| Message ID | 20241205123413.309388-1-nilay@linux.ibm.com |
|---|---|
| State | New |
| Headers | show |
| Series | [PATCHv2] cpumask: work around false-postive stringop-overread errors | expand |
On Fri, Dec 06, 2024 at 02:39:58PM +0530, Nilay Shroff wrote: > > Thank you Yuri for insightful comments! Please see my responses inline... > > On 12/5/24 21:53, Yury Norov wrote: > > On Thu, Dec 05, 2024 at 06:04:09PM +0530, Nilay Shroff wrote: > >> While building the powerpc code using gcc 13, I came across following > >> errors generated for kernel/padata.c file: > >> > >> CC kernel/padata.o > >> In file included from ./include/linux/string.h:390, > >> from ./arch/powerpc/include/asm/paca.h:16, > >> from ./arch/powerpc/include/asm/current.h:13, > >> from ./include/linux/thread_info.h:23, > >> from ./include/asm-generic/preempt.h:5, > >> from ./arch/powerpc/include/generated/asm/preempt.h:1, > >> from ./include/linux/preempt.h:79, > >> from ./include/linux/spinlock.h:56, > >> from ./include/linux/swait.h:7, > >> from ./include/linux/completion.h:12, > >> from kernel/padata.c:14: > >> In function ‘bitmap_copy’, > >> inlined from ‘cpumask_copy’ at ./include/linux/cpumask.h:839:2, > >> inlined from ‘__padata_set_cpumasks’ at kernel/padata.c:730:2: > >> ./include/linux/fortify-string.h:114:33: error: ‘__builtin_memcpy’ reading between 257 and 536870904 bytes from a region of size 256 [-Werror=stringop-overread] > >> 114 | #define __underlying_memcpy __builtin_memcpy > >> | ^ > >> ./include/linux/fortify-string.h:633:9: note: in expansion of macro ‘__underlying_memcpy’ > >> 633 | __underlying_##op(p, q, __fortify_size); \ > >> | ^~~~~~~~~~~~~ > >> ./include/linux/fortify-string.h:678:26: note: in expansion of macro ‘__fortify_memcpy_chk’ > >> 678 | #define memcpy(p, q, s) __fortify_memcpy_chk(p, q, s, \ > >> | ^~~~~~~~~~~~~~~~~~~~ > >> ./include/linux/bitmap.h:259:17: note: in expansion of macro ‘memcpy’ > >> 259 | memcpy(dst, src, len); > >> | ^~~~~~ > >> kernel/padata.c: In function ‘__padata_set_cpumasks’: > >> kernel/padata.c:713:48: note: source object ‘pcpumask’ of size [0, 256] > >> 713 | cpumask_var_t pcpumask, > >> | ~~~~~~~~~~~~~~^~~~~~~~ > >> In function ‘bitmap_copy’, > >> inlined from ‘cpumask_copy’ at ./include/linux/cpumask.h:839:2, > >> inlined from ‘__padata_set_cpumasks’ at kernel/padata.c:730:2: > >> ./include/linux/fortify-string.h:114:33: error: ‘__builtin_memcpy’ reading between 257 and 536870904 bytes from a region of size 256 [-Werror=stringop-overread] > >> 114 | #define __underlying_memcpy __builtin_memcpy > >> | ^ > >> ./include/linux/fortify-string.h:633:9: note: in expansion of macro ‘__underlying_memcpy’ > >> 633 | __underlying_##op(p, q, __fortify_size); \ > >> | ^~~~~~~~~~~~~ > >> ./include/linux/fortify-string.h:678:26: note: in expansion of macro ‘__fortify_memcpy_chk’ > >> 678 | #define memcpy(p, q, s) __fortify_memcpy_chk(p, q, s, \ > >> | ^~~~~~~~~~~~~~~~~~~~ > >> ./include/linux/bitmap.h:259:17: note: in expansion of macro ‘memcpy’ > >> 259 | memcpy(dst, src, len); > >> | ^~~~~~ > >> kernel/padata.c: In function ‘__padata_set_cpumasks’: > >> kernel/padata.c:713:48: note: source object ‘pcpumask’ of size [0, 256] > >> 713 | cpumask_var_t pcpumask, > >> | ~~~~~~~~~~~~~~^~~~~~~~ > >> > >> Apparently, above errors only manifests with GCC 13.x and config option > >> CONFIG_FORTIFY_SOURCE. Furthermore, if I use gcc 11.x or gcc 12.x then I > >> don't encounter above errors. Prima facie, these errors appear to be false- > > > > If it works for pre-GCC13, and likely for clang, you shouldn't disable it > > for them. It should be enabled for CONFIG_FORTIFY_SOURCE=n, as well. > > > > Check config CC_NO_ARRAY_BOUNDS for an example of how versioned flags > > are implemented. > > > > >> positive. Brian informed me that currently some efforts are underway by > >> GCC developers to emit more verbose information when GCC detects string > >> overflow errors and that might help to further narrow down the root cause > >> of this error. > > > > I'm 100% sure that Brian is a great person and his information is > > absolutely correct and complete. But this is just not how we write > > commit messages. > > > > Please avoid personal references, vague statements and news from > > the future. > > > Sure, I would do the needful for future patches. > > >> So for now, silence these errors using -Wno-stringop- > >> overread gcc option while building kernel/padata.c file until we find the > >> root cause. > > > > You didn't provide any evidence that this warning is specific for padata. > > > > Let me just show you the test matrix for the stringop-overread error: > > ARCH PowerPC: > compiler CONFIG_FORTIFY_SOURCE -Werror=stringop-overread > gcc 11.x Y N > gcc 11.x N N > gcc 12.x Y N > gcc 12.x N N > gcc 13.x Y Y > gcc 13.x N N > clang 18.x Y N > clang 18.x N N > > ARCH x86_64: > compiler CONFIG_FORTIFY_SOURCE -Werror=stringop-overread > gcc 11.x Y N > gcc 11.x N N > gcc 12.x Y N > gcc 12.x N N > gcc 13.x Y N > gcc 13.x N N > clang 18.x Y N > clang 18.x N N > > >From the above matrix, we could see that the sringop-overread error is only encountered > when we use gcc 13 on PowerPC machine and the stringop-overread error is seen only when we > enable CONFIG_FORTIFY_SOURCE. Furthermore, so far I've only encountered this error while > compiling kernel/padata.c file. > > > And indeed the subject states that this is a cpumasks-related warninig. > > Cpumask is a global subsystem. If you believe that this warning is > > false-positive, it may show up for any other random victim. Please > > suppress it globally. > > > Yes you were correct, this warning might appear for any other random victims. But as > I mentioned earlier, so far I've only encountered it with kernel/padata.c file. > So, if we want to reduce the blast radius then wouldn't it be sufficient to just silence > it only while compiling kernel/padata.c file? Or do you still suggest disabling it at > global level would be more helpful? I'm OK with either way moving forward. Please let > me know. You will reduce the radius significantly if you limit sringop-overread suppression to a specific config, compiler and architecture. Silencing random files is a gambling.
On Thu, Dec 05, 2024 at 06:04:09PM +0530, Nilay Shroff wrote: > While building the powerpc code using gcc 13, I came across following > errors generated for kernel/padata.c file: > > CC kernel/padata.o > In file included from ./include/linux/string.h:390, > from ./arch/powerpc/include/asm/paca.h:16, > from ./arch/powerpc/include/asm/current.h:13, > from ./include/linux/thread_info.h:23, > from ./include/asm-generic/preempt.h:5, > from ./arch/powerpc/include/generated/asm/preempt.h:1, > from ./include/linux/preempt.h:79, > from ./include/linux/spinlock.h:56, > from ./include/linux/swait.h:7, > from ./include/linux/completion.h:12, > from kernel/padata.c:14: > In function ‘bitmap_copy’, > inlined from ‘cpumask_copy’ at ./include/linux/cpumask.h:839:2, > inlined from ‘__padata_set_cpumasks’ at kernel/padata.c:730:2: > ./include/linux/fortify-string.h:114:33: error: ‘__builtin_memcpy’ reading between 257 and 536870904 bytes from a region of size 256 [-Werror=stringop-overread] > 114 | #define __underlying_memcpy __builtin_memcpy > | ^ > ./include/linux/fortify-string.h:633:9: note: in expansion of macro ‘__underlying_memcpy’ > 633 | __underlying_##op(p, q, __fortify_size); \ > | ^~~~~~~~~~~~~ > ./include/linux/fortify-string.h:678:26: note: in expansion of macro ‘__fortify_memcpy_chk’ > 678 | #define memcpy(p, q, s) __fortify_memcpy_chk(p, q, s, \ > | ^~~~~~~~~~~~~~~~~~~~ > ./include/linux/bitmap.h:259:17: note: in expansion of macro ‘memcpy’ > 259 | memcpy(dst, src, len); > | ^~~~~~ > kernel/padata.c: In function ‘__padata_set_cpumasks’: > kernel/padata.c:713:48: note: source object ‘pcpumask’ of size [0, 256] > 713 | cpumask_var_t pcpumask, > | ~~~~~~~~~~~~~~^~~~~~~~ > In function ‘bitmap_copy’, > inlined from ‘cpumask_copy’ at ./include/linux/cpumask.h:839:2, > inlined from ‘__padata_set_cpumasks’ at kernel/padata.c:730:2: > ./include/linux/fortify-string.h:114:33: error: ‘__builtin_memcpy’ reading between 257 and 536870904 bytes from a region of size 256 [-Werror=stringop-overread] > 114 | #define __underlying_memcpy __builtin_memcpy > | ^ > ./include/linux/fortify-string.h:633:9: note: in expansion of macro ‘__underlying_memcpy’ > 633 | __underlying_##op(p, q, __fortify_size); \ > | ^~~~~~~~~~~~~ > ./include/linux/fortify-string.h:678:26: note: in expansion of macro ‘__fortify_memcpy_chk’ > 678 | #define memcpy(p, q, s) __fortify_memcpy_chk(p, q, s, \ > | ^~~~~~~~~~~~~~~~~~~~ > ./include/linux/bitmap.h:259:17: note: in expansion of macro ‘memcpy’ > 259 | memcpy(dst, src, len); > | ^~~~~~ > kernel/padata.c: In function ‘__padata_set_cpumasks’: > kernel/padata.c:713:48: note: source object ‘pcpumask’ of size [0, 256] > 713 | cpumask_var_t pcpumask, > | ~~~~~~~~~~~~~~^~~~~~~~ > > Apparently, above errors only manifests with GCC 13.x and config option > CONFIG_FORTIFY_SOURCE. Furthermore, if I use gcc 11.x or gcc 12.x then I > don't encounter above errors. Prima facie, these errors appear to be false- > positive. Brian informed me that currently some efforts are underway by > GCC developers to emit more verbose information when GCC detects string > overflow errors and that might help to further narrow down the root cause > of this error. So for now, silence these errors using -Wno-stringop- > overread gcc option while building kernel/padata.c file until we find the > root cause. I'm hitting this now on Linus's tree using gcc14 on x86-64 so this isn't just a problem with your arch. Let me try this patch locally and see if it helps... thanks, greg k-h
On Sat, Dec 07, 2024 at 12:43:19PM +0100, Greg KH wrote: > On Thu, Dec 05, 2024 at 06:04:09PM +0530, Nilay Shroff wrote: > > While building the powerpc code using gcc 13, I came across following > > errors generated for kernel/padata.c file: > > > > CC kernel/padata.o > > In file included from ./include/linux/string.h:390, > > from ./arch/powerpc/include/asm/paca.h:16, > > from ./arch/powerpc/include/asm/current.h:13, > > from ./include/linux/thread_info.h:23, > > from ./include/asm-generic/preempt.h:5, > > from ./arch/powerpc/include/generated/asm/preempt.h:1, > > from ./include/linux/preempt.h:79, > > from ./include/linux/spinlock.h:56, > > from ./include/linux/swait.h:7, > > from ./include/linux/completion.h:12, > > from kernel/padata.c:14: > > In function ‘bitmap_copy’, > > inlined from ‘cpumask_copy’ at ./include/linux/cpumask.h:839:2, > > inlined from ‘__padata_set_cpumasks’ at kernel/padata.c:730:2: > > ./include/linux/fortify-string.h:114:33: error: ‘__builtin_memcpy’ reading between 257 and 536870904 bytes from a region of size 256 [-Werror=stringop-overread] > > 114 | #define __underlying_memcpy __builtin_memcpy > > | ^ > > ./include/linux/fortify-string.h:633:9: note: in expansion of macro ‘__underlying_memcpy’ > > 633 | __underlying_##op(p, q, __fortify_size); \ > > | ^~~~~~~~~~~~~ > > ./include/linux/fortify-string.h:678:26: note: in expansion of macro ‘__fortify_memcpy_chk’ > > 678 | #define memcpy(p, q, s) __fortify_memcpy_chk(p, q, s, \ > > | ^~~~~~~~~~~~~~~~~~~~ > > ./include/linux/bitmap.h:259:17: note: in expansion of macro ‘memcpy’ > > 259 | memcpy(dst, src, len); > > | ^~~~~~ > > kernel/padata.c: In function ‘__padata_set_cpumasks’: > > kernel/padata.c:713:48: note: source object ‘pcpumask’ of size [0, 256] > > 713 | cpumask_var_t pcpumask, > > | ~~~~~~~~~~~~~~^~~~~~~~ > > In function ‘bitmap_copy’, > > inlined from ‘cpumask_copy’ at ./include/linux/cpumask.h:839:2, > > inlined from ‘__padata_set_cpumasks’ at kernel/padata.c:730:2: > > ./include/linux/fortify-string.h:114:33: error: ‘__builtin_memcpy’ reading between 257 and 536870904 bytes from a region of size 256 [-Werror=stringop-overread] > > 114 | #define __underlying_memcpy __builtin_memcpy > > | ^ > > ./include/linux/fortify-string.h:633:9: note: in expansion of macro ‘__underlying_memcpy’ > > 633 | __underlying_##op(p, q, __fortify_size); \ > > | ^~~~~~~~~~~~~ > > ./include/linux/fortify-string.h:678:26: note: in expansion of macro ‘__fortify_memcpy_chk’ > > 678 | #define memcpy(p, q, s) __fortify_memcpy_chk(p, q, s, \ > > | ^~~~~~~~~~~~~~~~~~~~ > > ./include/linux/bitmap.h:259:17: note: in expansion of macro ‘memcpy’ > > 259 | memcpy(dst, src, len); > > | ^~~~~~ > > kernel/padata.c: In function ‘__padata_set_cpumasks’: > > kernel/padata.c:713:48: note: source object ‘pcpumask’ of size [0, 256] > > 713 | cpumask_var_t pcpumask, > > | ~~~~~~~~~~~~~~^~~~~~~~ > > > > Apparently, above errors only manifests with GCC 13.x and config option > > CONFIG_FORTIFY_SOURCE. Furthermore, if I use gcc 11.x or gcc 12.x then I > > don't encounter above errors. Prima facie, these errors appear to be false- > > positive. Brian informed me that currently some efforts are underway by > > GCC developers to emit more verbose information when GCC detects string > > overflow errors and that might help to further narrow down the root cause > > of this error. So for now, silence these errors using -Wno-stringop- > > overread gcc option while building kernel/padata.c file until we find the > > root cause. > > I'm hitting this now on Linus's tree using gcc14 on x86-64 so this isn't > just a problem with your arch. > > Let me try this patch locally and see if it helps... Yes, fixes the build for me, so either this is a real fix, or something else needs to be done for it, so I'll give a: Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> for now. thanks, greg k-h
On 12/7/24 17:14, Greg KH wrote: > On Sat, Dec 07, 2024 at 12:43:19PM +0100, Greg KH wrote: >> On Thu, Dec 05, 2024 at 06:04:09PM +0530, Nilay Shroff wrote: >>> While building the powerpc code using gcc 13, I came across following >>> errors generated for kernel/padata.c file: >>> >>> CC kernel/padata.o >>> In file included from ./include/linux/string.h:390, >>> from ./arch/powerpc/include/asm/paca.h:16, >>> from ./arch/powerpc/include/asm/current.h:13, >>> from ./include/linux/thread_info.h:23, >>> from ./include/asm-generic/preempt.h:5, >>> from ./arch/powerpc/include/generated/asm/preempt.h:1, >>> from ./include/linux/preempt.h:79, >>> from ./include/linux/spinlock.h:56, >>> from ./include/linux/swait.h:7, >>> from ./include/linux/completion.h:12, >>> from kernel/padata.c:14: >>> In function ‘bitmap_copy’, >>> inlined from ‘cpumask_copy’ at ./include/linux/cpumask.h:839:2, >>> inlined from ‘__padata_set_cpumasks’ at kernel/padata.c:730:2: >>> ./include/linux/fortify-string.h:114:33: error: ‘__builtin_memcpy’ reading between 257 and 536870904 bytes from a region of size 256 [-Werror=stringop-overread] >>> 114 | #define __underlying_memcpy __builtin_memcpy >>> | ^ >>> ./include/linux/fortify-string.h:633:9: note: in expansion of macro ‘__underlying_memcpy’ >>> 633 | __underlying_##op(p, q, __fortify_size); \ >>> | ^~~~~~~~~~~~~ >>> ./include/linux/fortify-string.h:678:26: note: in expansion of macro ‘__fortify_memcpy_chk’ >>> 678 | #define memcpy(p, q, s) __fortify_memcpy_chk(p, q, s, \ >>> | ^~~~~~~~~~~~~~~~~~~~ >>> ./include/linux/bitmap.h:259:17: note: in expansion of macro ‘memcpy’ >>> 259 | memcpy(dst, src, len); >>> | ^~~~~~ >>> kernel/padata.c: In function ‘__padata_set_cpumasks’: >>> kernel/padata.c:713:48: note: source object ‘pcpumask’ of size [0, 256] >>> 713 | cpumask_var_t pcpumask, >>> | ~~~~~~~~~~~~~~^~~~~~~~ >>> In function ‘bitmap_copy’, >>> inlined from ‘cpumask_copy’ at ./include/linux/cpumask.h:839:2, >>> inlined from ‘__padata_set_cpumasks’ at kernel/padata.c:730:2: >>> ./include/linux/fortify-string.h:114:33: error: ‘__builtin_memcpy’ reading between 257 and 536870904 bytes from a region of size 256 [-Werror=stringop-overread] >>> 114 | #define __underlying_memcpy __builtin_memcpy >>> | ^ >>> ./include/linux/fortify-string.h:633:9: note: in expansion of macro ‘__underlying_memcpy’ >>> 633 | __underlying_##op(p, q, __fortify_size); \ >>> | ^~~~~~~~~~~~~ >>> ./include/linux/fortify-string.h:678:26: note: in expansion of macro ‘__fortify_memcpy_chk’ >>> 678 | #define memcpy(p, q, s) __fortify_memcpy_chk(p, q, s, \ >>> | ^~~~~~~~~~~~~~~~~~~~ >>> ./include/linux/bitmap.h:259:17: note: in expansion of macro ‘memcpy’ >>> 259 | memcpy(dst, src, len); >>> | ^~~~~~ >>> kernel/padata.c: In function ‘__padata_set_cpumasks’: >>> kernel/padata.c:713:48: note: source object ‘pcpumask’ of size [0, 256] >>> 713 | cpumask_var_t pcpumask, >>> | ~~~~~~~~~~~~~~^~~~~~~~ >>> >>> Apparently, above errors only manifests with GCC 13.x and config option >>> CONFIG_FORTIFY_SOURCE. Furthermore, if I use gcc 11.x or gcc 12.x then I >>> don't encounter above errors. Prima facie, these errors appear to be false- >>> positive. Brian informed me that currently some efforts are underway by >>> GCC developers to emit more verbose information when GCC detects string >>> overflow errors and that might help to further narrow down the root cause >>> of this error. So for now, silence these errors using -Wno-stringop- >>> overread gcc option while building kernel/padata.c file until we find the >>> root cause. >> >> I'm hitting this now on Linus's tree using gcc14 on x86-64 so this isn't >> just a problem with your arch. Thanks Greg for confirming that this is not isolated to PowerPC!! >> >> Let me try this patch locally and see if it helps... > > Yes, fixes the build for me, so either this is a real fix, or something > else needs to be done for it, so I'll give a: > > Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > > for now. Okay so now we've an evidence confirming that this is no longer PowerPC specific issue. Hence as Yury suggested, in another mail[1], fixing this error by disabling stringop-overread globally for GCC13+ and CONFIG_FORTIFY_SOURCE=n, I will spin a new patch and submit it. [1] https://lore.kernel.org/all/Z1HTdtvNjm-nZSvJ@yury-ThinkPad/ Thanks, --Nilay
On Sun, Dec 08, 2024 at 03:51:10PM +0530, Nilay Shroff wrote: > > > On 12/7/24 17:14, Greg KH wrote: > > On Sat, Dec 07, 2024 at 12:43:19PM +0100, Greg KH wrote: > >> On Thu, Dec 05, 2024 at 06:04:09PM +0530, Nilay Shroff wrote: > >>> While building the powerpc code using gcc 13, I came across following > >>> errors generated for kernel/padata.c file: > >>> > >>> CC kernel/padata.o > >>> In file included from ./include/linux/string.h:390, > >>> from ./arch/powerpc/include/asm/paca.h:16, > >>> from ./arch/powerpc/include/asm/current.h:13, > >>> from ./include/linux/thread_info.h:23, > >>> from ./include/asm-generic/preempt.h:5, > >>> from ./arch/powerpc/include/generated/asm/preempt.h:1, > >>> from ./include/linux/preempt.h:79, > >>> from ./include/linux/spinlock.h:56, > >>> from ./include/linux/swait.h:7, > >>> from ./include/linux/completion.h:12, > >>> from kernel/padata.c:14: > >>> In function ‘bitmap_copy’, > >>> inlined from ‘cpumask_copy’ at ./include/linux/cpumask.h:839:2, > >>> inlined from ‘__padata_set_cpumasks’ at kernel/padata.c:730:2: > >>> ./include/linux/fortify-string.h:114:33: error: ‘__builtin_memcpy’ reading between 257 and 536870904 bytes from a region of size 256 [-Werror=stringop-overread] > >>> 114 | #define __underlying_memcpy __builtin_memcpy > >>> | ^ > >>> ./include/linux/fortify-string.h:633:9: note: in expansion of macro ‘__underlying_memcpy’ > >>> 633 | __underlying_##op(p, q, __fortify_size); \ > >>> | ^~~~~~~~~~~~~ > >>> ./include/linux/fortify-string.h:678:26: note: in expansion of macro ‘__fortify_memcpy_chk’ > >>> 678 | #define memcpy(p, q, s) __fortify_memcpy_chk(p, q, s, \ > >>> | ^~~~~~~~~~~~~~~~~~~~ > >>> ./include/linux/bitmap.h:259:17: note: in expansion of macro ‘memcpy’ > >>> 259 | memcpy(dst, src, len); > >>> | ^~~~~~ > >>> kernel/padata.c: In function ‘__padata_set_cpumasks’: > >>> kernel/padata.c:713:48: note: source object ‘pcpumask’ of size [0, 256] > >>> 713 | cpumask_var_t pcpumask, > >>> | ~~~~~~~~~~~~~~^~~~~~~~ > >>> In function ‘bitmap_copy’, > >>> inlined from ‘cpumask_copy’ at ./include/linux/cpumask.h:839:2, > >>> inlined from ‘__padata_set_cpumasks’ at kernel/padata.c:730:2: > >>> ./include/linux/fortify-string.h:114:33: error: ‘__builtin_memcpy’ reading between 257 and 536870904 bytes from a region of size 256 [-Werror=stringop-overread] > >>> 114 | #define __underlying_memcpy __builtin_memcpy > >>> | ^ > >>> ./include/linux/fortify-string.h:633:9: note: in expansion of macro ‘__underlying_memcpy’ > >>> 633 | __underlying_##op(p, q, __fortify_size); \ > >>> | ^~~~~~~~~~~~~ > >>> ./include/linux/fortify-string.h:678:26: note: in expansion of macro ‘__fortify_memcpy_chk’ > >>> 678 | #define memcpy(p, q, s) __fortify_memcpy_chk(p, q, s, \ > >>> | ^~~~~~~~~~~~~~~~~~~~ > >>> ./include/linux/bitmap.h:259:17: note: in expansion of macro ‘memcpy’ > >>> 259 | memcpy(dst, src, len); > >>> | ^~~~~~ > >>> kernel/padata.c: In function ‘__padata_set_cpumasks’: > >>> kernel/padata.c:713:48: note: source object ‘pcpumask’ of size [0, 256] > >>> 713 | cpumask_var_t pcpumask, > >>> | ~~~~~~~~~~~~~~^~~~~~~~ > >>> > >>> Apparently, above errors only manifests with GCC 13.x and config option > >>> CONFIG_FORTIFY_SOURCE. Furthermore, if I use gcc 11.x or gcc 12.x then I > >>> don't encounter above errors. Prima facie, these errors appear to be false- > >>> positive. Brian informed me that currently some efforts are underway by > >>> GCC developers to emit more verbose information when GCC detects string > >>> overflow errors and that might help to further narrow down the root cause > >>> of this error. So for now, silence these errors using -Wno-stringop- > >>> overread gcc option while building kernel/padata.c file until we find the > >>> root cause. > >> > >> I'm hitting this now on Linus's tree using gcc14 on x86-64 so this isn't > >> just a problem with your arch. > Thanks Greg for confirming that this is not isolated to PowerPC!! > >> > >> Let me try this patch locally and see if it helps... > > > > Yes, fixes the build for me, so either this is a real fix, or something > > else needs to be done for it, so I'll give a: > > > > Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > > > > for now. > Okay so now we've an evidence confirming that this is no longer PowerPC specific > issue. Hence as Yury suggested, in another mail[1], fixing this error by disabling > stringop-overread globally for GCC13+ and CONFIG_FORTIFY_SOURCE=n, I will spin a > new patch and submit it. > > [1] https://lore.kernel.org/all/Z1HTdtvNjm-nZSvJ@yury-ThinkPad/ That feels wrong, unless this is a compiler bug. And if it's a compiler bug, can we fix the compiler please or at least submit a bug to the gcc developers? I'm slowly moving all my boxes/builds over to using clang to build the kernel due to rust kernel work, so I guess I can do that here as well as I don't think this issue shows up for that compiler, right? thanks, greg k-h
On 12/8/24 18:58, Greg KH wrote: > On Sun, Dec 08, 2024 at 03:51:10PM +0530, Nilay Shroff wrote: >> >> >> On 12/7/24 17:14, Greg KH wrote: >>> On Sat, Dec 07, 2024 at 12:43:19PM +0100, Greg KH wrote: >>>> On Thu, Dec 05, 2024 at 06:04:09PM +0530, Nilay Shroff wrote: >>>>> While building the powerpc code using gcc 13, I came across following >>>>> errors generated for kernel/padata.c file: >>>>> >>>>> CC kernel/padata.o >>>>> In file included from ./include/linux/string.h:390, >>>>> from ./arch/powerpc/include/asm/paca.h:16, >>>>> from ./arch/powerpc/include/asm/current.h:13, >>>>> from ./include/linux/thread_info.h:23, >>>>> from ./include/asm-generic/preempt.h:5, >>>>> from ./arch/powerpc/include/generated/asm/preempt.h:1, >>>>> from ./include/linux/preempt.h:79, >>>>> from ./include/linux/spinlock.h:56, >>>>> from ./include/linux/swait.h:7, >>>>> from ./include/linux/completion.h:12, >>>>> from kernel/padata.c:14: >>>>> In function ‘bitmap_copy’, >>>>> inlined from ‘cpumask_copy’ at ./include/linux/cpumask.h:839:2, >>>>> inlined from ‘__padata_set_cpumasks’ at kernel/padata.c:730:2: >>>>> ./include/linux/fortify-string.h:114:33: error: ‘__builtin_memcpy’ reading between 257 and 536870904 bytes from a region of size 256 [-Werror=stringop-overread] >>>>> 114 | #define __underlying_memcpy __builtin_memcpy >>>>> | ^ >>>>> ./include/linux/fortify-string.h:633:9: note: in expansion of macro ‘__underlying_memcpy’ >>>>> 633 | __underlying_##op(p, q, __fortify_size); \ >>>>> | ^~~~~~~~~~~~~ >>>>> ./include/linux/fortify-string.h:678:26: note: in expansion of macro ‘__fortify_memcpy_chk’ >>>>> 678 | #define memcpy(p, q, s) __fortify_memcpy_chk(p, q, s, \ >>>>> | ^~~~~~~~~~~~~~~~~~~~ >>>>> ./include/linux/bitmap.h:259:17: note: in expansion of macro ‘memcpy’ >>>>> 259 | memcpy(dst, src, len); >>>>> | ^~~~~~ >>>>> kernel/padata.c: In function ‘__padata_set_cpumasks’: >>>>> kernel/padata.c:713:48: note: source object ‘pcpumask’ of size [0, 256] >>>>> 713 | cpumask_var_t pcpumask, >>>>> | ~~~~~~~~~~~~~~^~~~~~~~ >>>>> In function ‘bitmap_copy’, >>>>> inlined from ‘cpumask_copy’ at ./include/linux/cpumask.h:839:2, >>>>> inlined from ‘__padata_set_cpumasks’ at kernel/padata.c:730:2: >>>>> ./include/linux/fortify-string.h:114:33: error: ‘__builtin_memcpy’ reading between 257 and 536870904 bytes from a region of size 256 [-Werror=stringop-overread] >>>>> 114 | #define __underlying_memcpy __builtin_memcpy >>>>> | ^ >>>>> ./include/linux/fortify-string.h:633:9: note: in expansion of macro ‘__underlying_memcpy’ >>>>> 633 | __underlying_##op(p, q, __fortify_size); \ >>>>> | ^~~~~~~~~~~~~ >>>>> ./include/linux/fortify-string.h:678:26: note: in expansion of macro ‘__fortify_memcpy_chk’ >>>>> 678 | #define memcpy(p, q, s) __fortify_memcpy_chk(p, q, s, \ >>>>> | ^~~~~~~~~~~~~~~~~~~~ >>>>> ./include/linux/bitmap.h:259:17: note: in expansion of macro ‘memcpy’ >>>>> 259 | memcpy(dst, src, len); >>>>> | ^~~~~~ >>>>> kernel/padata.c: In function ‘__padata_set_cpumasks’: >>>>> kernel/padata.c:713:48: note: source object ‘pcpumask’ of size [0, 256] >>>>> 713 | cpumask_var_t pcpumask, >>>>> | ~~~~~~~~~~~~~~^~~~~~~~ >>>>> >>>>> Apparently, above errors only manifests with GCC 13.x and config option >>>>> CONFIG_FORTIFY_SOURCE. Furthermore, if I use gcc 11.x or gcc 12.x then I >>>>> don't encounter above errors. Prima facie, these errors appear to be false- >>>>> positive. Brian informed me that currently some efforts are underway by >>>>> GCC developers to emit more verbose information when GCC detects string >>>>> overflow errors and that might help to further narrow down the root cause >>>>> of this error. So for now, silence these errors using -Wno-stringop- >>>>> overread gcc option while building kernel/padata.c file until we find the >>>>> root cause. >>>> >>>> I'm hitting this now on Linus's tree using gcc14 on x86-64 so this isn't >>>> just a problem with your arch. >> Thanks Greg for confirming that this is not isolated to PowerPC!! >>>> >>>> Let me try this patch locally and see if it helps... >>> >>> Yes, fixes the build for me, so either this is a real fix, or something >>> else needs to be done for it, so I'll give a: >>> >>> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> >>> >>> for now. >> Okay so now we've an evidence confirming that this is no longer PowerPC specific >> issue. Hence as Yury suggested, in another mail[1], fixing this error by disabling >> stringop-overread globally for GCC13+ and CONFIG_FORTIFY_SOURCE=n, I will spin a >> new patch and submit it. >> >> [1] https://lore.kernel.org/all/Z1HTdtvNjm-nZSvJ@yury-ThinkPad/ > > That feels wrong, unless this is a compiler bug. And if it's a compiler > bug, can we fix the compiler please or at least submit a bug to the gcc > developers? > Yes this seems to be a compiler bug. Please see here : [1] https://lore.kernel.org/all/202411021337.85E9BB06@keescook/ [2] https://gcc.gnu.org/pipermail/gcc-patches/2024-October/666872.html > I'm slowly moving all my boxes/builds over to using clang to build the > kernel due to rust kernel work, so I guess I can do that here as well as > I don't think this issue shows up for that compiler, right? > Yes this error doesn't show up for LLVM/clang. We've two options here: 1) To disable this error globally for GCC-13+ until we find the root cause. Maybe when GCC folks add more diagnostics and contexts around -Wstringop-* compiler warning as discussed in [2] above. or 2) Silence this error only for file kernel/padata.c compiling which this error manifests as of today. Yury suggested option #1 above so that we may avoid random victims hitting this error. What do you suggest? Thanks, --Nilay
On Sun, Dec 08, 2024 at 07:21:48PM +0530, Nilay Shroff wrote: > > > On 12/8/24 18:58, Greg KH wrote: > > On Sun, Dec 08, 2024 at 03:51:10PM +0530, Nilay Shroff wrote: > >> > >> > >> On 12/7/24 17:14, Greg KH wrote: > >>> On Sat, Dec 07, 2024 at 12:43:19PM +0100, Greg KH wrote: > >>>> On Thu, Dec 05, 2024 at 06:04:09PM +0530, Nilay Shroff wrote: > >>>>> While building the powerpc code using gcc 13, I came across following > >>>>> errors generated for kernel/padata.c file: > >>>>> > >>>>> CC kernel/padata.o > >>>>> In file included from ./include/linux/string.h:390, > >>>>> from ./arch/powerpc/include/asm/paca.h:16, > >>>>> from ./arch/powerpc/include/asm/current.h:13, > >>>>> from ./include/linux/thread_info.h:23, > >>>>> from ./include/asm-generic/preempt.h:5, > >>>>> from ./arch/powerpc/include/generated/asm/preempt.h:1, > >>>>> from ./include/linux/preempt.h:79, > >>>>> from ./include/linux/spinlock.h:56, > >>>>> from ./include/linux/swait.h:7, > >>>>> from ./include/linux/completion.h:12, > >>>>> from kernel/padata.c:14: > >>>>> In function ‘bitmap_copy’, > >>>>> inlined from ‘cpumask_copy’ at ./include/linux/cpumask.h:839:2, > >>>>> inlined from ‘__padata_set_cpumasks’ at kernel/padata.c:730:2: > >>>>> ./include/linux/fortify-string.h:114:33: error: ‘__builtin_memcpy’ reading between 257 and 536870904 bytes from a region of size 256 [-Werror=stringop-overread] > >>>>> 114 | #define __underlying_memcpy __builtin_memcpy > >>>>> | ^ > >>>>> ./include/linux/fortify-string.h:633:9: note: in expansion of macro ‘__underlying_memcpy’ > >>>>> 633 | __underlying_##op(p, q, __fortify_size); \ > >>>>> | ^~~~~~~~~~~~~ > >>>>> ./include/linux/fortify-string.h:678:26: note: in expansion of macro ‘__fortify_memcpy_chk’ > >>>>> 678 | #define memcpy(p, q, s) __fortify_memcpy_chk(p, q, s, \ > >>>>> | ^~~~~~~~~~~~~~~~~~~~ > >>>>> ./include/linux/bitmap.h:259:17: note: in expansion of macro ‘memcpy’ > >>>>> 259 | memcpy(dst, src, len); > >>>>> | ^~~~~~ > >>>>> kernel/padata.c: In function ‘__padata_set_cpumasks’: > >>>>> kernel/padata.c:713:48: note: source object ‘pcpumask’ of size [0, 256] > >>>>> 713 | cpumask_var_t pcpumask, > >>>>> | ~~~~~~~~~~~~~~^~~~~~~~ > >>>>> In function ‘bitmap_copy’, > >>>>> inlined from ‘cpumask_copy’ at ./include/linux/cpumask.h:839:2, > >>>>> inlined from ‘__padata_set_cpumasks’ at kernel/padata.c:730:2: > >>>>> ./include/linux/fortify-string.h:114:33: error: ‘__builtin_memcpy’ reading between 257 and 536870904 bytes from a region of size 256 [-Werror=stringop-overread] > >>>>> 114 | #define __underlying_memcpy __builtin_memcpy > >>>>> | ^ > >>>>> ./include/linux/fortify-string.h:633:9: note: in expansion of macro ‘__underlying_memcpy’ > >>>>> 633 | __underlying_##op(p, q, __fortify_size); \ > >>>>> | ^~~~~~~~~~~~~ > >>>>> ./include/linux/fortify-string.h:678:26: note: in expansion of macro ‘__fortify_memcpy_chk’ > >>>>> 678 | #define memcpy(p, q, s) __fortify_memcpy_chk(p, q, s, \ > >>>>> | ^~~~~~~~~~~~~~~~~~~~ > >>>>> ./include/linux/bitmap.h:259:17: note: in expansion of macro ‘memcpy’ > >>>>> 259 | memcpy(dst, src, len); > >>>>> | ^~~~~~ > >>>>> kernel/padata.c: In function ‘__padata_set_cpumasks’: > >>>>> kernel/padata.c:713:48: note: source object ‘pcpumask’ of size [0, 256] > >>>>> 713 | cpumask_var_t pcpumask, > >>>>> | ~~~~~~~~~~~~~~^~~~~~~~ > >>>>> > >>>>> Apparently, above errors only manifests with GCC 13.x and config option > >>>>> CONFIG_FORTIFY_SOURCE. Furthermore, if I use gcc 11.x or gcc 12.x then I > >>>>> don't encounter above errors. Prima facie, these errors appear to be false- > >>>>> positive. Brian informed me that currently some efforts are underway by > >>>>> GCC developers to emit more verbose information when GCC detects string > >>>>> overflow errors and that might help to further narrow down the root cause > >>>>> of this error. So for now, silence these errors using -Wno-stringop- > >>>>> overread gcc option while building kernel/padata.c file until we find the > >>>>> root cause. > >>>> > >>>> I'm hitting this now on Linus's tree using gcc14 on x86-64 so this isn't > >>>> just a problem with your arch. > >> Thanks Greg for confirming that this is not isolated to PowerPC!! > >>>> > >>>> Let me try this patch locally and see if it helps... > >>> > >>> Yes, fixes the build for me, so either this is a real fix, or something > >>> else needs to be done for it, so I'll give a: > >>> > >>> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > >>> > >>> for now. > >> Okay so now we've an evidence confirming that this is no longer PowerPC specific > >> issue. Hence as Yury suggested, in another mail[1], fixing this error by disabling > >> stringop-overread globally for GCC13+ and CONFIG_FORTIFY_SOURCE=n, I will spin a > >> new patch and submit it. > >> > >> [1] https://lore.kernel.org/all/Z1HTdtvNjm-nZSvJ@yury-ThinkPad/ > > > > That feels wrong, unless this is a compiler bug. And if it's a compiler > > bug, can we fix the compiler please or at least submit a bug to the gcc > > developers? > > > Yes this seems to be a compiler bug. Please see here : > [1] https://lore.kernel.org/all/202411021337.85E9BB06@keescook/ > [2] https://gcc.gnu.org/pipermail/gcc-patches/2024-October/666872.html > > > I'm slowly moving all my boxes/builds over to using clang to build the > > kernel due to rust kernel work, so I guess I can do that here as well as > > I don't think this issue shows up for that compiler, right? > > > Yes this error doesn't show up for LLVM/clang. We've two options here: > 1) To disable this error globally for GCC-13+ until we find the root cause. Maybe when > GCC folks add more diagnostics and contexts around -Wstringop-* compiler warning as > discussed in [2] above. > or > 2) Silence this error only for file kernel/padata.c compiling which this error manifests > as of today. > > Yury suggested option #1 above so that we may avoid random victims hitting this error. > What do you suggest? I suggest the hardening maintainers should decide, as this is their area and feature they are supporting, not me :) thanks, greg k-h
On 12/8/24 19:27, Greg KH wrote: > On Sun, Dec 08, 2024 at 07:21:48PM +0530, Nilay Shroff wrote: >> >> >> On 12/8/24 18:58, Greg KH wrote: >>> On Sun, Dec 08, 2024 at 03:51:10PM +0530, Nilay Shroff wrote: >>>> >>>> >>>> On 12/7/24 17:14, Greg KH wrote: >>>>> On Sat, Dec 07, 2024 at 12:43:19PM +0100, Greg KH wrote: >>>>>> On Thu, Dec 05, 2024 at 06:04:09PM +0530, Nilay Shroff wrote: >>>>>>> While building the powerpc code using gcc 13, I came across following >>>>>>> errors generated for kernel/padata.c file: >>>>>>> >>>>>>> CC kernel/padata.o >>>>>>> In file included from ./include/linux/string.h:390, >>>>>>> from ./arch/powerpc/include/asm/paca.h:16, >>>>>>> from ./arch/powerpc/include/asm/current.h:13, >>>>>>> from ./include/linux/thread_info.h:23, >>>>>>> from ./include/asm-generic/preempt.h:5, >>>>>>> from ./arch/powerpc/include/generated/asm/preempt.h:1, >>>>>>> from ./include/linux/preempt.h:79, >>>>>>> from ./include/linux/spinlock.h:56, >>>>>>> from ./include/linux/swait.h:7, >>>>>>> from ./include/linux/completion.h:12, >>>>>>> from kernel/padata.c:14: >>>>>>> In function ‘bitmap_copy’, >>>>>>> inlined from ‘cpumask_copy’ at ./include/linux/cpumask.h:839:2, >>>>>>> inlined from ‘__padata_set_cpumasks’ at kernel/padata.c:730:2: >>>>>>> ./include/linux/fortify-string.h:114:33: error: ‘__builtin_memcpy’ reading between 257 and 536870904 bytes from a region of size 256 [-Werror=stringop-overread] >>>>>>> 114 | #define __underlying_memcpy __builtin_memcpy >>>>>>> | ^ >>>>>>> ./include/linux/fortify-string.h:633:9: note: in expansion of macro ‘__underlying_memcpy’ >>>>>>> 633 | __underlying_##op(p, q, __fortify_size); \ >>>>>>> | ^~~~~~~~~~~~~ >>>>>>> ./include/linux/fortify-string.h:678:26: note: in expansion of macro ‘__fortify_memcpy_chk’ >>>>>>> 678 | #define memcpy(p, q, s) __fortify_memcpy_chk(p, q, s, \ >>>>>>> | ^~~~~~~~~~~~~~~~~~~~ >>>>>>> ./include/linux/bitmap.h:259:17: note: in expansion of macro ‘memcpy’ >>>>>>> 259 | memcpy(dst, src, len); >>>>>>> | ^~~~~~ >>>>>>> kernel/padata.c: In function ‘__padata_set_cpumasks’: >>>>>>> kernel/padata.c:713:48: note: source object ‘pcpumask’ of size [0, 256] >>>>>>> 713 | cpumask_var_t pcpumask, >>>>>>> | ~~~~~~~~~~~~~~^~~~~~~~ >>>>>>> In function ‘bitmap_copy’, >>>>>>> inlined from ‘cpumask_copy’ at ./include/linux/cpumask.h:839:2, >>>>>>> inlined from ‘__padata_set_cpumasks’ at kernel/padata.c:730:2: >>>>>>> ./include/linux/fortify-string.h:114:33: error: ‘__builtin_memcpy’ reading between 257 and 536870904 bytes from a region of size 256 [-Werror=stringop-overread] >>>>>>> 114 | #define __underlying_memcpy __builtin_memcpy >>>>>>> | ^ >>>>>>> ./include/linux/fortify-string.h:633:9: note: in expansion of macro ‘__underlying_memcpy’ >>>>>>> 633 | __underlying_##op(p, q, __fortify_size); \ >>>>>>> | ^~~~~~~~~~~~~ >>>>>>> ./include/linux/fortify-string.h:678:26: note: in expansion of macro ‘__fortify_memcpy_chk’ >>>>>>> 678 | #define memcpy(p, q, s) __fortify_memcpy_chk(p, q, s, \ >>>>>>> | ^~~~~~~~~~~~~~~~~~~~ >>>>>>> ./include/linux/bitmap.h:259:17: note: in expansion of macro ‘memcpy’ >>>>>>> 259 | memcpy(dst, src, len); >>>>>>> | ^~~~~~ >>>>>>> kernel/padata.c: In function ‘__padata_set_cpumasks’: >>>>>>> kernel/padata.c:713:48: note: source object ‘pcpumask’ of size [0, 256] >>>>>>> 713 | cpumask_var_t pcpumask, >>>>>>> | ~~~~~~~~~~~~~~^~~~~~~~ >>>>>>> >>>>>>> Apparently, above errors only manifests with GCC 13.x and config option >>>>>>> CONFIG_FORTIFY_SOURCE. Furthermore, if I use gcc 11.x or gcc 12.x then I >>>>>>> don't encounter above errors. Prima facie, these errors appear to be false- >>>>>>> positive. Brian informed me that currently some efforts are underway by >>>>>>> GCC developers to emit more verbose information when GCC detects string >>>>>>> overflow errors and that might help to further narrow down the root cause >>>>>>> of this error. So for now, silence these errors using -Wno-stringop- >>>>>>> overread gcc option while building kernel/padata.c file until we find the >>>>>>> root cause. >>>>>> >>>>>> I'm hitting this now on Linus's tree using gcc14 on x86-64 so this isn't >>>>>> just a problem with your arch. >>>> Thanks Greg for confirming that this is not isolated to PowerPC!! >>>>>> >>>>>> Let me try this patch locally and see if it helps... >>>>> >>>>> Yes, fixes the build for me, so either this is a real fix, or something >>>>> else needs to be done for it, so I'll give a: >>>>> >>>>> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> >>>>> >>>>> for now. >>>> Okay so now we've an evidence confirming that this is no longer PowerPC specific >>>> issue. Hence as Yury suggested, in another mail[1], fixing this error by disabling >>>> stringop-overread globally for GCC13+ and CONFIG_FORTIFY_SOURCE=n, I will spin a >>>> new patch and submit it. >>>> >>>> [1] https://lore.kernel.org/all/Z1HTdtvNjm-nZSvJ@yury-ThinkPad/ >>> >>> That feels wrong, unless this is a compiler bug. And if it's a compiler >>> bug, can we fix the compiler please or at least submit a bug to the gcc >>> developers? >>> >> Yes this seems to be a compiler bug. Please see here : >> [1] https://lore.kernel.org/all/202411021337.85E9BB06@keescook/ >> [2] https://gcc.gnu.org/pipermail/gcc-patches/2024-October/666872.html >> >>> I'm slowly moving all my boxes/builds over to using clang to build the >>> kernel due to rust kernel work, so I guess I can do that here as well as >>> I don't think this issue shows up for that compiler, right? >>> >> Yes this error doesn't show up for LLVM/clang. We've two options here: >> 1) To disable this error globally for GCC-13+ until we find the root cause. Maybe when >> GCC folks add more diagnostics and contexts around -Wstringop-* compiler warning as >> discussed in [2] above. >> or >> 2) Silence this error only for file kernel/padata.c compiling which this error manifests >> as of today. >> >> Yury suggested option #1 above so that we may avoid random victims hitting this error. >> What do you suggest? > > I suggest the hardening maintainers should decide, as this is their area > and feature they are supporting, not me :) > Alright, then I would go ahead with option #1, as Yury suggested, for now while I spin next patch and keep in Cc all hardening maintainers to decide the disposition. Thanks, --Nilay
diff --git a/kernel/Makefile b/kernel/Makefile index 87866b037fbe..03242d8870c7 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -120,6 +120,10 @@ obj-$(CONFIG_CFI_CLANG) += cfi.o obj-$(CONFIG_PERF_EVENTS) += events/ obj-$(CONFIG_USER_RETURN_NOTIFIER) += user-return-notifier.o + +# Silence the false positive stringop-overread errors on GCC 13+ +CFLAGS_padata.o += $(call cc-disable-warning, stringop-overread) + obj-$(CONFIG_PADATA) += padata.o obj-$(CONFIG_JUMP_LABEL) += jump_label.o obj-$(CONFIG_CONTEXT_TRACKING) += context_tracking.o
While building the powerpc code using gcc 13, I came across following errors generated for kernel/padata.c file: CC kernel/padata.o In file included from ./include/linux/string.h:390, from ./arch/powerpc/include/asm/paca.h:16, from ./arch/powerpc/include/asm/current.h:13, from ./include/linux/thread_info.h:23, from ./include/asm-generic/preempt.h:5, from ./arch/powerpc/include/generated/asm/preempt.h:1, from ./include/linux/preempt.h:79, from ./include/linux/spinlock.h:56, from ./include/linux/swait.h:7, from ./include/linux/completion.h:12, from kernel/padata.c:14: In function ‘bitmap_copy’, inlined from ‘cpumask_copy’ at ./include/linux/cpumask.h:839:2, inlined from ‘__padata_set_cpumasks’ at kernel/padata.c:730:2: ./include/linux/fortify-string.h:114:33: error: ‘__builtin_memcpy’ reading between 257 and 536870904 bytes from a region of size 256 [-Werror=stringop-overread] 114 | #define __underlying_memcpy __builtin_memcpy | ^ ./include/linux/fortify-string.h:633:9: note: in expansion of macro ‘__underlying_memcpy’ 633 | __underlying_##op(p, q, __fortify_size); \ | ^~~~~~~~~~~~~ ./include/linux/fortify-string.h:678:26: note: in expansion of macro ‘__fortify_memcpy_chk’ 678 | #define memcpy(p, q, s) __fortify_memcpy_chk(p, q, s, \ | ^~~~~~~~~~~~~~~~~~~~ ./include/linux/bitmap.h:259:17: note: in expansion of macro ‘memcpy’ 259 | memcpy(dst, src, len); | ^~~~~~ kernel/padata.c: In function ‘__padata_set_cpumasks’: kernel/padata.c:713:48: note: source object ‘pcpumask’ of size [0, 256] 713 | cpumask_var_t pcpumask, | ~~~~~~~~~~~~~~^~~~~~~~ In function ‘bitmap_copy’, inlined from ‘cpumask_copy’ at ./include/linux/cpumask.h:839:2, inlined from ‘__padata_set_cpumasks’ at kernel/padata.c:730:2: ./include/linux/fortify-string.h:114:33: error: ‘__builtin_memcpy’ reading between 257 and 536870904 bytes from a region of size 256 [-Werror=stringop-overread] 114 | #define __underlying_memcpy __builtin_memcpy | ^ ./include/linux/fortify-string.h:633:9: note: in expansion of macro ‘__underlying_memcpy’ 633 | __underlying_##op(p, q, __fortify_size); \ | ^~~~~~~~~~~~~ ./include/linux/fortify-string.h:678:26: note: in expansion of macro ‘__fortify_memcpy_chk’ 678 | #define memcpy(p, q, s) __fortify_memcpy_chk(p, q, s, \ | ^~~~~~~~~~~~~~~~~~~~ ./include/linux/bitmap.h:259:17: note: in expansion of macro ‘memcpy’ 259 | memcpy(dst, src, len); | ^~~~~~ kernel/padata.c: In function ‘__padata_set_cpumasks’: kernel/padata.c:713:48: note: source object ‘pcpumask’ of size [0, 256] 713 | cpumask_var_t pcpumask, | ~~~~~~~~~~~~~~^~~~~~~~ Apparently, above errors only manifests with GCC 13.x and config option CONFIG_FORTIFY_SOURCE. Furthermore, if I use gcc 11.x or gcc 12.x then I don't encounter above errors. Prima facie, these errors appear to be false- positive. Brian informed me that currently some efforts are underway by GCC developers to emit more verbose information when GCC detects string overflow errors and that might help to further narrow down the root cause of this error. So for now, silence these errors using -Wno-stringop- overread gcc option while building kernel/padata.c file until we find the root cause. Link: https://lore.kernel.org/all/7cbbd751-8332-4ab2-afa7-8c353834772a@linux.ibm.com/ Cc: briannorris@chromium.org Cc: kees@kernel.org Cc: nathan@kernel.org Cc: yury.norov@gmail.com Cc: steffen.klassert@secunet.com Cc: daniel.m.jordan@oracle.com Cc: linux-crypto@vger.kernel.org Cc: linux@weissschuh.net Cc: gjoyce@ibm.com Reviewed-by: Brian Norris <briannorris@chromium.org> Signed-off-by: Nilay Shroff <nilay@linux.ibm.com> --- Changes from v1: - Fix spell error in the commit message (Brian Norris) - Add commentary around change to note that changes are needed to avoid false positive on gcc 13+ (Brian Norris) - Add the kerenl/padata.c file maintainers (Brian Norris) --- kernel/Makefile | 4 ++++ 1 file changed, 4 insertions(+)