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malloc: make malloc fail with requests larger than PTRDIFF_MAX (BZ#23741)

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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.
This commit is contained in:
Adhemerval Zanella
2018-12-18 16:30:56 -02:00
parent 52faba65f8
commit 9bf8e29ca1
12 changed files with 227 additions and 88 deletions
Download Patch File Download Diff File Expand all files Collapse all files

49
malloc/tst-malloc-too-large.c
View File

@@ -72,13 +72,28 @@ test_large_allocations (size_t size)
void * ptr_to_realloc;
test_setup ();
DIAG_PUSH_NEEDS_COMMENT;
#if __GNUC_PREREQ (7, 0)
/* GCC 7 warns about too-large allocations; here we want to test
that they fail. */
DIAG_IGNORE_NEEDS_COMMENT (7, "-Walloc-size-larger-than=");
#endif
TEST_VERIFY (malloc (size) == NULL);
#if __GNUC_PREREQ (7, 0)
DIAG_POP_NEEDS_COMMENT;
#endif
TEST_VERIFY (errno == ENOMEM);
ptr_to_realloc = malloc (16);
TEST_VERIFY_EXIT (ptr_to_realloc != NULL);
test_setup ();
#if __GNUC_PREREQ (7, 0)
DIAG_IGNORE_NEEDS_COMMENT (7, "-Walloc-size-larger-than=");
#endif
TEST_VERIFY (realloc (ptr_to_realloc, size) == NULL);
#if __GNUC_PREREQ (7, 0)
DIAG_POP_NEEDS_COMMENT;
#endif
TEST_VERIFY (errno == ENOMEM);
free (ptr_to_realloc);
@@ -135,7 +150,13 @@ test_large_aligned_allocations (size_t size)
for (align = 1; align <= pagesize; align *= 2)
{
test_setup ();
#if __GNUC_PREREQ (7, 0)
DIAG_IGNORE_NEEDS_COMMENT (7, "-Walloc-size-larger-than=");
#endif
TEST_VERIFY (memalign (align, size) == NULL);
#if __GNUC_PREREQ (7, 0)
DIAG_POP_NEEDS_COMMENT;
#endif
TEST_VERIFY (errno == ENOMEM);
/* posix_memalign expects an alignment that is a power of 2 *and* a
@@ -151,7 +172,13 @@ test_large_aligned_allocations (size_t size)
if ((size % align) == 0)
{
test_setup ();
#if __GNUC_PREREQ (7, 0)
DIAG_IGNORE_NEEDS_COMMENT (7, "-Walloc-size-larger-than=");
#endif
TEST_VERIFY (aligned_alloc (align, size) == NULL);
#if __GNUC_PREREQ (7, 0)
DIAG_POP_NEEDS_COMMENT;
#endif
TEST_VERIFY (errno == ENOMEM);
}
}
@@ -159,11 +186,23 @@ test_large_aligned_allocations (size_t size)
/* Both valloc and pvalloc return page-aligned memory. */
test_setup ();
#if __GNUC_PREREQ (7, 0)
DIAG_IGNORE_NEEDS_COMMENT (7, "-Walloc-size-larger-than=");
#endif
TEST_VERIFY (valloc (size) == NULL);
#if __GNUC_PREREQ (7, 0)
DIAG_POP_NEEDS_COMMENT;
#endif
TEST_VERIFY (errno == ENOMEM);
test_setup ();
#if __GNUC_PREREQ (7, 0)
DIAG_IGNORE_NEEDS_COMMENT (7, "-Walloc-size-larger-than=");
#endif
TEST_VERIFY (pvalloc (size) == NULL);
#if __GNUC_PREREQ (7, 0)
DIAG_POP_NEEDS_COMMENT;
#endif
TEST_VERIFY (errno == ENOMEM);
}
@@ -226,6 +265,16 @@ do_test (void)
test_large_aligned_allocations (SIZE_MAX - i);
}
/* Allocation larger than PTRDIFF_MAX does play well with C standard,
since pointer subtraction within the object might overflow ptrdiff_t
resulting in undefined behavior. To prevent it malloc function fail
for such allocations. */
for (size_t i = 1; i <= FOURTEEN_ON_BITS; i++)
{
test_large_allocations (PTRDIFF_MAX + i);
test_large_aligned_allocations (PTRDIFF_MAX + i);
}
#if __WORDSIZE >= 64
/* On 64-bit targets, we need to test a much wider range of too-large
sizes, so we test at intervals of (1 << 50) that allocation sizes