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author | Adhemerval Zanella <adhemerval.zanella@linaro.org> | 2018-12-18 16:30:56 -0200 |
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committer | Adhemerval Zanella <adhemerval.zanella@linaro.org> | 2019-04-18 17:30:06 -0300 |
commit | 9bf8e29ca136094f73f69f725f15c51facc97206 (patch) | |
tree | f79f17de093731f502dee183888a491d88263f78 /NEWS | |
parent | 52faba65f84ee5a8d82ff813bcfa0ee5f4d480cf (diff) | |
download | glibc-9bf8e29ca136094f73f69f725f15c51facc97206.tar.gz glibc-9bf8e29ca136094f73f69f725f15c51facc97206.tar.xz glibc-9bf8e29ca136094f73f69f725f15c51facc97206.zip |
malloc: make malloc fail with requests larger than PTRDIFF_MAX (BZ#23741)
As discussed previously on libc-alpha [1], this patch follows up the idea and add both the __attribute_alloc_size__ on malloc functions (malloc, calloc, realloc, reallocarray, valloc, pvalloc, and memalign) and limit maximum requested allocation size to up PTRDIFF_MAX (taking into consideration internal padding and alignment). This aligns glibc with gcc expected size defined by default warning -Walloc-size-larger-than value which warns for allocation larger than PTRDIFF_MAX. It also aligns with gcc expectation regarding libc and expected size, such as described in PR#67999 [2] and previously discussed ISO C11 issues [3] on libc-alpha. From the RFC thread [4] and previous discussion, it seems that consensus is only to limit such requested size for malloc functions, not the system allocation one (mmap, sbrk, etc.). The implementation changes checked_request2size to check for both overflow and maximum object size up to PTRDIFF_MAX. No additional checks are done on sysmalloc, so it can still issue mmap with values larger than PTRDIFF_T depending on the requested size. The __attribute_alloc_size__ is for functions that return a pointer only, which means it cannot be applied to posix_memalign (see remarks in GCC PR#87683 [5]). The runtimes checks to limit maximum requested allocation size does applies to posix_memalign. Checked on x86_64-linux-gnu and i686-linux-gnu. [1] https://sourceware.org/ml/libc-alpha/2018-11/msg00223.html [2] https://gcc.gnu.org/bugzilla//show_bug.cgi?id=67999 [3] https://sourceware.org/ml/libc-alpha/2011-12/msg00066.html [4] https://sourceware.org/ml/libc-alpha/2018-11/msg00224.html [5] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87683 [BZ #23741] * malloc/hooks.c (malloc_check, realloc_check): Use __builtin_add_overflow on overflow check and adapt to checked_request2size change. * malloc/malloc.c (__libc_malloc, __libc_realloc, _mid_memalign, __libc_pvalloc, __libc_calloc, _int_memalign): Limit maximum allocation size to PTRDIFF_MAX. (REQUEST_OUT_OF_RANGE): Remove macro. (checked_request2size): Change to inline function and limit maximum requested size to PTRDIFF_MAX. (__libc_malloc, __libc_realloc, _int_malloc, _int_memalign): Limit maximum allocation size to PTRDIFF_MAX. (_mid_memalign): Use _int_memalign call for overflow check. (__libc_pvalloc): Use __builtin_add_overflow on overflow check. (__libc_calloc): Use __builtin_mul_overflow for overflow check and limit maximum requested size to PTRDIFF_MAX. * malloc/malloc.h (malloc, calloc, realloc, reallocarray, memalign, valloc, pvalloc): Add __attribute_alloc_size__. * stdlib/stdlib.h (malloc, realloc, reallocarray, valloc): Likewise. * malloc/tst-malloc-too-large.c (do_test): Add check for allocation larger than PTRDIFF_MAX. * malloc/tst-memalign.c (do_test): Disable -Walloc-size-larger-than= around tests of malloc with negative sizes. * malloc/tst-posix_memalign.c (do_test): Likewise. * malloc/tst-pvalloc.c (do_test): Likewise. * malloc/tst-valloc.c (do_test): Likewise. * malloc/tst-reallocarray.c (do_test): Replace call to reallocarray with resulting size allocation larger than PTRDIFF_MAX with reallocarray_nowarn. (reallocarray_nowarn): New function. * NEWS: Mention the malloc function semantic change.
Diffstat (limited to 'NEWS')
-rw-r--r-- | NEWS | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/NEWS b/NEWS index b58e2469d4..db1ca8125b 100644 --- a/NEWS +++ b/NEWS @@ -160,6 +160,12 @@ Deprecated and removed features, and other changes affecting compatibility: as all functions that call vscanf, vfscanf, or vsscanf are annotated with __attribute__ ((format (scanf, ...))). +* Memory allocation functions malloc, calloc, realloc, reallocarray, valloc, + pvalloc, memalign, and posix_memalign fail now with total object size + larger than PTRDIFF_MAX. This is to avoid potential undefined behavior with + pointer subtraction within the allocated object, where results might + overflow the ptrdiff_t type. + Changes to build and runtime requirements: * Python 3.4 or later is required to build the GNU C Library. |