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authorArjun Shankar <arjun.is@lostca.se>2018-01-18 16:47:06 +0000
committerArjun Shankar <arjun@redhat.com>2018-01-18 17:55:45 +0100
commit8e448310d74b283c5cd02b9ed7fb997b47bf9b22 (patch)
treea5cb99be6773177cf14683cbf10ecbc34a7dc82c /malloc
parent80647883cf5847c8b6b0197e9703eb04222496b6 (diff)
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Fix integer overflows in internal memalign and malloc functions [BZ #22343]
When posix_memalign is called with an alignment less than MALLOC_ALIGNMENT and a requested size close to SIZE_MAX, it falls back to malloc code (because the alignment of a block returned by malloc is sufficient to satisfy the call). In this case, an integer overflow in _int_malloc leads to posix_memalign incorrectly returning successfully. Upon fixing this and writing a somewhat thorough regression test, it was discovered that when posix_memalign is called with an alignment larger than MALLOC_ALIGNMENT (so it uses _int_memalign instead) and a requested size close to SIZE_MAX, a different integer overflow in _int_memalign leads to posix_memalign incorrectly returning successfully. Both integer overflows affect other memory allocation functions that use _int_malloc (one affected malloc in x86) or _int_memalign as well. This commit fixes both integer overflows. In addition to this, it adds a regression test to guard against false successful allocations by the following memory allocation functions when called with too-large allocation sizes and, where relevant, various valid alignments: malloc, realloc, calloc, reallocarray, memalign, posix_memalign, aligned_alloc, valloc, and pvalloc.
Diffstat (limited to 'malloc')
-rw-r--r--malloc/Makefile1
-rw-r--r--malloc/malloc.c30
-rw-r--r--malloc/tst-malloc-too-large.c253
3 files changed, 276 insertions, 8 deletions
diff --git a/malloc/Makefile b/malloc/Makefile
index 4266c2b66b3..17873e67c4b 100644
--- a/malloc/Makefile
+++ b/malloc/Makefile
@@ -36,6 +36,7 @@ tests := mallocbug tst-malloc tst-valloc tst-calloc tst-obstack \
tst-alloc_buffer \
tst-malloc-tcache-leak \
tst-malloc_info \
+ tst-malloc-too-large \
tests-static := \
tst-interpose-static-nothread \
diff --git a/malloc/malloc.c b/malloc/malloc.c
index f5aafd2c051..7889fb19613 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -1224,14 +1224,21 @@ nextchunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
MINSIZE : \
((req) + SIZE_SZ + MALLOC_ALIGN_MASK) & ~MALLOC_ALIGN_MASK)
-/* Same, except also perform argument check */
-
-#define checked_request2size(req, sz) \
- if (REQUEST_OUT_OF_RANGE (req)) { \
- __set_errno (ENOMEM); \
- return 0; \
- } \
- (sz) = request2size (req);
+/* Same, except also perform an argument and result check. First, we check
+ that the padding done by request2size didn't result in an integer
+ overflow. Then we check (using REQUEST_OUT_OF_RANGE) that the resulting
+ size isn't so large that a later alignment would lead to another integer
+ overflow. */
+#define checked_request2size(req, sz) \
+({ \
+ (sz) = request2size (req); \
+ if (((sz) < (req)) \
+ || REQUEST_OUT_OF_RANGE (sz)) \
+ { \
+ __set_errno (ENOMEM); \
+ return 0; \
+ } \
+})
/*
--------------- Physical chunk operations ---------------
@@ -4678,6 +4685,13 @@ _int_memalign (mstate av, size_t alignment, size_t bytes)
*/
+ /* Check for overflow. */
+ if (nb > SIZE_MAX - alignment - MINSIZE)
+ {
+ __set_errno (ENOMEM);
+ return 0;
+ }
+
/* Call malloc with worst case padding to hit alignment. */
m = (char *) (_int_malloc (av, nb + alignment + MINSIZE));
diff --git a/malloc/tst-malloc-too-large.c b/malloc/tst-malloc-too-large.c
new file mode 100644
index 00000000000..10fb1365280
--- /dev/null
+++ b/malloc/tst-malloc-too-large.c
@@ -0,0 +1,253 @@
+/* Test and verify that too-large memory allocations fail with ENOMEM.
+ Copyright (C) 2018 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+/* Bug 22375 reported a regression in malloc where if after malloc'ing then
+ free'ing a small block of memory, malloc is then called with a really
+ large size argument (close to SIZE_MAX): instead of returning NULL and
+ setting errno to ENOMEM, malloc incorrectly returns the previously
+ allocated block instead. Bug 22343 reported a similar case where
+ posix_memalign incorrectly returns successfully when called with an with
+ a really large size argument.
+
+ Both of these were caused by integer overflows in the allocator when it
+ was trying to pad the requested size to allow for book-keeping or
+ alignment. This test guards against such bugs by repeatedly allocating
+ and freeing small blocks of memory then trying to allocate various block
+ sizes larger than the memory bus width of 64-bit targets, or almost
+ as large as SIZE_MAX on 32-bit targets supported by glibc. In each case,
+ it verifies that such impossibly large allocations correctly fail. */
+
+
+#include <stdlib.h>
+#include <malloc.h>
+#include <errno.h>
+#include <stdint.h>
+#include <sys/resource.h>
+#include <libc-diag.h>
+#include <support/check.h>
+#include <unistd.h>
+#include <sys/param.h>
+
+
+/* This function prepares for each 'too-large memory allocation' test by
+ performing a small successful malloc/free and resetting errno prior to
+ the actual test. */
+static void
+test_setup (void)
+{
+ void *volatile ptr = malloc (16);
+ TEST_VERIFY_EXIT (ptr != NULL);
+ free (ptr);
+ errno = 0;
+}
+
+
+/* This function tests each of:
+ - malloc (SIZE)
+ - realloc (PTR_FOR_REALLOC, SIZE)
+ - for various values of NMEMB:
+ - calloc (NMEMB, SIZE/NMEMB)
+ - calloc (SIZE/NMEMB, NMEMB)
+ - reallocarray (PTR_FOR_REALLOC, NMEMB, SIZE/NMEMB)
+ - reallocarray (PTR_FOR_REALLOC, SIZE/NMEMB, NMEMB)
+ and precedes each of these tests with a small malloc/free before it. */
+static void
+test_large_allocations (size_t size)
+{
+ void * ptr_to_realloc;
+
+ test_setup ();
+ TEST_VERIFY (malloc (size) == NULL);
+ TEST_VERIFY (errno == ENOMEM);
+
+ ptr_to_realloc = malloc (16);
+ TEST_VERIFY_EXIT (ptr_to_realloc != NULL);
+ test_setup ();
+ TEST_VERIFY (realloc (ptr_to_realloc, size) == NULL);
+ TEST_VERIFY (errno == ENOMEM);
+ free (ptr_to_realloc);
+
+ for (size_t nmemb = 1; nmemb <= 8; nmemb *= 2)
+ if ((size % nmemb) == 0)
+ {
+ test_setup ();
+ TEST_VERIFY (calloc (nmemb, size / nmemb) == NULL);
+ TEST_VERIFY (errno == ENOMEM);
+
+ test_setup ();
+ TEST_VERIFY (calloc (size / nmemb, nmemb) == NULL);
+ TEST_VERIFY (errno == ENOMEM);
+
+ ptr_to_realloc = malloc (16);
+ TEST_VERIFY_EXIT (ptr_to_realloc != NULL);
+ test_setup ();
+ TEST_VERIFY (reallocarray (ptr_to_realloc, nmemb, size / nmemb) == NULL);
+ TEST_VERIFY (errno == ENOMEM);
+ free (ptr_to_realloc);
+
+ ptr_to_realloc = malloc (16);
+ TEST_VERIFY_EXIT (ptr_to_realloc != NULL);
+ test_setup ();
+ TEST_VERIFY (reallocarray (ptr_to_realloc, size / nmemb, nmemb) == NULL);
+ TEST_VERIFY (errno == ENOMEM);
+ free (ptr_to_realloc);
+ }
+ else
+ break;
+}
+
+
+static long pagesize;
+
+/* This function tests the following aligned memory allocation functions
+ using several valid alignments and precedes each allocation test with a
+ small malloc/free before it:
+ memalign, posix_memalign, aligned_alloc, valloc, pvalloc. */
+static void
+test_large_aligned_allocations (size_t size)
+{
+ /* ptr stores the result of posix_memalign but since all those calls
+ should fail, posix_memalign should never change ptr. We set it to
+ NULL here and later on we check that it remains NULL after each
+ posix_memalign call. */
+ void * ptr = NULL;
+
+ size_t align;
+
+ /* All aligned memory allocation functions expect an alignment that is a
+ power of 2. Given this, we test each of them with every valid
+ alignment from 1 thru PAGESIZE. */
+ for (align = 1; align <= pagesize; align *= 2)
+ {
+ test_setup ();
+ TEST_VERIFY (memalign (align, size) == NULL);
+ TEST_VERIFY (errno == ENOMEM);
+
+ /* posix_memalign expects an alignment that is a power of 2 *and* a
+ multiple of sizeof (void *). */
+ if ((align % sizeof (void *)) == 0)
+ {
+ test_setup ();
+ TEST_VERIFY (posix_memalign (&ptr, align, size) == ENOMEM);
+ TEST_VERIFY (ptr == NULL);
+ }
+
+ /* aligned_alloc expects a size that is a multiple of alignment. */
+ if ((size % align) == 0)
+ {
+ test_setup ();
+ TEST_VERIFY (aligned_alloc (align, size) == NULL);
+ TEST_VERIFY (errno == ENOMEM);
+ }
+ }
+
+ /* Both valloc and pvalloc return page-aligned memory. */
+
+ test_setup ();
+ TEST_VERIFY (valloc (size) == NULL);
+ TEST_VERIFY (errno == ENOMEM);
+
+ test_setup ();
+ TEST_VERIFY (pvalloc (size) == NULL);
+ TEST_VERIFY (errno == ENOMEM);
+}
+
+
+#define FOURTEEN_ON_BITS ((1UL << 14) - 1)
+#define FIFTY_ON_BITS ((1UL << 50) - 1)
+
+
+static int
+do_test (void)
+{
+
+#if __WORDSIZE >= 64
+
+ /* This test assumes that none of the supported targets have an address
+ bus wider than 50 bits, and that therefore allocations for sizes wider
+ than 50 bits will fail. Here, we ensure that the assumption continues
+ to be true in the future when we might have address buses wider than 50
+ bits. */
+
+ struct rlimit alloc_size_limit
+ = {
+ .rlim_cur = FIFTY_ON_BITS,
+ .rlim_max = FIFTY_ON_BITS
+ };
+
+ setrlimit (RLIMIT_AS, &alloc_size_limit);
+
+#endif /* __WORDSIZE >= 64 */
+
+ 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
+
+ /* Aligned memory allocation functions need to be tested up to alignment
+ size equivalent to page size, which should be a power of 2. */
+ pagesize = sysconf (_SC_PAGESIZE);
+ TEST_VERIFY_EXIT (powerof2 (pagesize));
+
+ /* Loop 1: Ensure that all allocations with SIZE close to SIZE_MAX, i.e.
+ in the range (SIZE_MAX - 2^14, SIZE_MAX], fail.
+
+ We can expect that this range of allocation sizes will always lead to
+ an allocation failure on both 64 and 32 bit targets, because:
+
+ 1. no currently supported 64-bit target has an address bus wider than
+ 50 bits -- and (2^64 - 2^14) is much wider than that;
+
+ 2. on 32-bit targets, even though 2^32 is only 4 GB and potentially
+ addressable, glibc itself is more than 2^14 bytes in size, and
+ therefore once glibc is loaded, less than (2^32 - 2^14) bytes remain
+ available. */
+
+ for (size_t i = 0; i <= FOURTEEN_ON_BITS; i++)
+ {
+ test_large_allocations (SIZE_MAX - i);
+ test_large_aligned_allocations (SIZE_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
+ ranging from SIZE_MAX down to (1 << 50) fail:
+ The 14 MSBs are decremented starting from "all ON" going down to 1,
+ the 50 LSBs are "all ON" and then "all OFF" during every iteration. */
+ for (size_t msbs = FOURTEEN_ON_BITS; msbs >= 1; msbs--)
+ {
+ size_t size = (msbs << 50) | FIFTY_ON_BITS;
+ test_large_allocations (size);
+ test_large_aligned_allocations (size);
+
+ size = msbs << 50;
+ test_large_allocations (size);
+ test_large_aligned_allocations (size);
+ }
+#endif /* __WORDSIZE >= 64 */
+
+ DIAG_POP_NEEDS_COMMENT;
+
+ return 0;
+}
+
+
+#include <support/test-driver.c>