| Message ID | 1511438786-32436-1-git-send-email-adhemerval.zanella@linaro.org |
|---|---|
| State | New |
| Headers | show |
| Series | posix: Call internal free on fallback p{read,write}v on Linux (BZ#22457) | expand |
On 11/23/2017 01:06 PM, Adhemerval Zanella wrote: > As described in BZ#22457 an interpose malloc can free an invalid > pointer for fallback preadv implementation. Fortunately this is > just and issue on microblaze-linux-gnu running kernels older than > 3.15. > > This patch fixes it by calling internal free (__libc_free). Another > possible option would be replace posix_memalign/free with a mmap/unmap, > however this is pessimization since it will two more syscalls necessary > for each preadv/pwritev call. This will break static malloc interposition because some of the functions in malloc/malloc.o are not weak. With an interposed malloc, the glibc malloc may not have been initialized, so you will have to supply your own locking here, too. I think you should use mmap/munmap. Thanks, Florian
On 23/11/2017 10:25, Florian Weimer wrote: > On 11/23/2017 01:06 PM, Adhemerval Zanella wrote: >> As described in BZ#22457 an interpose malloc can free an invalid >> pointer for fallback preadv implementation. Fortunately this is >> just and issue on microblaze-linux-gnu running kernels older than >> 3.15. >> >> This patch fixes it by calling internal free (__libc_free). Another >> possible option would be replace posix_memalign/free with a mmap/unmap, >> however this is pessimization since it will two more syscalls necessary >> for each preadv/pwritev call. > > This will break static malloc interposition because some of the functions in malloc/malloc.o are not weak. > > With an interposed malloc, the glibc malloc may not have been initialized, so you will have to supply your own locking here, too. > > I think you should use mmap/munmap. Sigh, so it basically means we can't use internal malloc symbol to avoid interposition. Right, mmap seems a better alternative for this.
diff --git a/include/malloc.h b/include/malloc.h index d4cd9a5..4b99dbc 100644 --- a/include/malloc.h +++ b/include/malloc.h @@ -14,5 +14,20 @@ extern __typeof (__malloc_check_init) __malloc_check_init attribute_hidden; struct malloc_state; typedef struct malloc_state *mstate; +extern void * __libc_malloc (size_t) attribute_hidden; +libc_hidden_proto (__libc_malloc) + +extern void __libc_free (void*) attribute_hidden; +libc_hidden_proto (__libc_free) + +extern void * __libc_realloc (void *, size_t) attribute_hidden; +libc_hidden_proto (__libc_realloc) + +extern void * __libc_memalign (size_t, size_t) attribute_hidden; +libc_hidden_proto (__libc_memalign) + +extern int __libc_mallopt (int, int) attribute_hidden; +libc_hidden_proto (__libc_mallopt) + # endif /* !_ISOMAC */ #endif diff --git a/malloc/malloc.c b/malloc/malloc.c index 2999ac4..5746193 100644 --- a/malloc/malloc.c +++ b/malloc/malloc.c @@ -500,8 +500,6 @@ void *(*__morecore)(ptrdiff_t) = __default_morecore; differs across systems, but is in all cases less than the maximum representable value of a size_t. */ -void* __libc_malloc(size_t); -libc_hidden_proto (__libc_malloc) /* free(void* p) @@ -514,8 +512,6 @@ libc_hidden_proto (__libc_malloc) when possible, automatically trigger operations that give back unused memory to the system, thus reducing program footprint. */ -void __libc_free(void*); -libc_hidden_proto (__libc_free) /* calloc(size_t n_elements, size_t element_size); @@ -551,8 +547,6 @@ void* __libc_calloc(size_t, size_t); The old unix realloc convention of allowing the last-free'd chunk to be used as an argument to realloc is not supported. */ -void* __libc_realloc(void*, size_t); -libc_hidden_proto (__libc_realloc) /* memalign(size_t alignment, size_t n); @@ -566,8 +560,6 @@ libc_hidden_proto (__libc_realloc) Overreliance on memalign is a sure way to fragment space. */ -void* __libc_memalign(size_t, size_t); -libc_hidden_proto (__libc_memalign) /* valloc(size_t n); @@ -599,8 +591,6 @@ void* __libc_valloc(size_t); M_MMAP_THRESHOLD -3 128*1024 any (or 0 if no MMAP support) M_MMAP_MAX -4 65536 any (0 disables use of mmap) */ -int __libc_mallopt(int, int); -libc_hidden_proto (__libc_mallopt) /* diff --git a/sysdeps/posix/preadv_common.c b/sysdeps/posix/preadv_common.c index 37efdc0..c650435 100644 --- a/sysdeps/posix/preadv_common.c +++ b/sysdeps/posix/preadv_common.c @@ -78,6 +78,6 @@ PREADV (int fd, const struct iovec *vector, int count, OFF_T offset) } end: - free (buffer); + __libc_free (buffer); return bytes_read; } diff --git a/sysdeps/posix/pwritev_common.c b/sysdeps/posix/pwritev_common.c index 0383065..6c364f8 100644 --- a/sysdeps/posix/pwritev_common.c +++ b/sysdeps/posix/pwritev_common.c @@ -66,7 +66,7 @@ PWRITEV (int fd, const struct iovec *vector, int count, OFF_T offset) ssize_t ret = PWRITE (fd, buffer, bytes, offset); - free (buffer); + __libc_free (buffer); return ret; }