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Thu, 5 Dec 2024 12:34:59 +0000 (GMT) From: Nilay Shroff To: linux-kernel@vger.kernel.org Cc: Nilay Shroff , briannorris@chromium.org, kees@kernel.org, nathan@kernel.org, yury.norov@gmail.com, steffen.klassert@secunet.com, daniel.m.jordan@oracle.com, linux-crypto@vger.kernel.org, linux@weissschuh.net, gjoyce@ibm.com Subject: [PATCHv2] cpumask: work around false-postive stringop-overread errors Date: Thu, 5 Dec 2024 18:04:09 +0530 Message-ID: <20241205123413.309388-1-nilay@linux.ibm.com> X-Mailer: git-send-email 2.45.2 Precedence: bulk X-Mailing-List: linux-crypto@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: GcK8_Kxy7R5GmRzrur814ZPhoJ1XsabR X-Proofpoint-GUID: QSKJ51AB-5YuxaLZqJTASMV__SCsY58l X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1051,Hydra:6.0.680,FMLib:17.12.62.30 definitions=2024-10-15_01,2024-10-11_01,2024-09-30_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1011 impostorscore=0 mlxscore=0 suspectscore=0 mlxlogscore=999 priorityscore=1501 bulkscore=0 phishscore=0 adultscore=0 malwarescore=0 spamscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2411120000 definitions=main-2412050090 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 Signed-off-by: Nilay Shroff Acked-by: Greg Kroah-Hartman --- 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(+) 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