When the malloc subsystem detects some kind of memory corruption,
depending on the configuration it prints the error, a backtrace, a
memory map and then aborts the process. In this process, the
backtrace() call may result in a call to malloc, resulting in
various kinds of problematic behavior.
In one case, the malloc it calls may detect a corruption and call
backtrace again, and a stack overflow may result due to the infinite
recursion. In another case, the malloc it calls may deadlock on an
arena lock with the malloc (or free, realloc, etc.) that detected the
corruption. In yet another case, if the program is linked with
pthreads, backtrace may do a pthread_once initialization, which
deadlocks on itself.
In all these cases, the program exit is not as intended. This is
avoidable by marking the arena that malloc detected a corruption on,
as unusable. The following patch does that. Features of this patch
are as follows:
- A flag is added to the mstate struct of the arena to indicate if the
arena is corrupt.
- The flag is checked whenever malloc functions try to get a lock on
an arena. If the arena is unusable, a NULL is returned, causing the
malloc to use mmap or try the next arena.
- malloc_printerr sets the corrupt flag on the arena when it detects a
corruption
- free does not concern itself with the flag at all. It is not
important since the backtrace workflow does not need free. A free
in a parallel thread may cause another corruption, but that's not
new
- The flag check and set are not atomic and may race. This is fine
since we don't care about contention during the flag check. We want
to make sure that the malloc call in the backtrace does not trip on
itself and all that action happens in the same thread and not across
threads.
I verified that the test case does not show any regressions due to
this patch. I also ran the malloc benchmarks and found an
insignificant difference in timings (< 2%).
* malloc/Makefile (tests): New test case tst-malloc-backtrace.
* malloc/arena.c (arena_lock): Check if arena is corrupt.
(reused_arena): Find a non-corrupt arena.
(heap_trim): Pass arena to unlink.
* malloc/hooks.c (malloc_check_get_size): Pass arena to
malloc_printerr.
(top_check): Likewise.
(free_check): Likewise.
(realloc_check): Likewise.
* malloc/malloc.c (malloc_printerr): Add arena argument.
(unlink): Likewise.
(munmap_chunk): Adjust.
(ARENA_CORRUPTION_BIT): New macro.
(arena_is_corrupt): Likewise.
(set_arena_corrupt): Likewise.
(sysmalloc): Use mmap if there are no usable arenas.
(_int_malloc): Likewise.
(__libc_malloc): Don't fail if arena_get returns NULL.
(_mid_memalign): Likewise.
(__libc_calloc): Likewise.
(__libc_realloc): Adjust for additional argument to
malloc_printerr.
(_int_free): Likewise.
(malloc_consolidate): Likewise.
(_int_realloc): Likewise.
(_int_memalign): Don't touch corrupt arenas.
* malloc/tst-malloc-backtrace.c: New test case.
This seems to have been left behind as an artifact of some old changes
and can now be merged. Verified that the only generated code change
on x86_64 is that of line numbers in asserts, like so:
@@ -27253,7 +27253,7 @@ Disassembly of section .text:
416f09: 48 89 42 20 mov %rax,0x20(%rdx)
416f0d: e9 7e f6 ff ff jmpq 416590 <_int_free+0x230>
416f12: b9 3f 9f 4a 00 mov $0x4a9f3f,%ecx
- 416f17: ba d5 0f 00 00 mov $0xfd5,%edx
+ 416f17: ba d6 0f 00 00 mov $0xfd6,%edx
416f1c: be a8 9b 4a 00 mov $0x4a9ba8,%esi
416f21: bf 6a 9c 4a 00 mov $0x4a9c6a,%edi
416f26: e8 45 e8 ff ff callq 415770 <__malloc_assert>
We are replacing all of the bespoke alignment code with
ALIGN_UP, ALIGN_DOWN, PTR_ALIGN_UP, and PTR_ALIGN_DOWN.
This cleans up malloc/malloc.c, malloc/arena.c, and
elf/dl-reloc.c. It also makes all the code consistently
use pagesize, and powerof2 as required.
Code size is reduced with the removal of precomputed
pagemask, and use of pagesize instead. No measurable
difference in performance.
No regressions on x86_64.
malloc_info is defined in the same file as malloc and free, but is not
an ISO C function, so should be a weak symbol. This patch makes it
so.
Tested for x86_64 (testsuite, and that disassembly of installed shared
libraries is unchanged by the patch).
[BZ #17570]
* malloc/malloc.c (malloc_info): Rename to __malloc_info and
define as weak alias of __malloc_info.
Due to my bad review suggestion for the fix for BZ #15089 a check
was removed from systrim to prevent sbrk being called with a zero
argument. Add the check back to avoid this useless work.
ChangeLog:
2014-06-19 Will Newton <will.newton@linaro.org>
* malloc/malloc.c (systrim): If extra is zero then return
early.
The current malloc_info xml output only has information about
allocations on the heap. Display information about number of mappings
and total mmapped size to this to complete the picture.
The nested function mi_arena was removed from malloc_info
and made into a non-nested static inline function of the same
name with the correct set of arguments passed from malloc_info.
This enables building glibc with compilers that don't support
nested functions. Future work on malloc_info should remove these
functions entirely to support JSON format output. Therefore we
do the minimum required to remove the nested function.
MALLOC_DEBUG is set optionally on the command line. Default the value
to zero if it is not set on the command line, and test its value
with #if rather than #ifdef. Verified the code is identical before
and after this change apart from line numbers.
ChangeLog:
2014-04-11 Will Newton <will.newton@linaro.org>
* malloc/malloc.c [!MALLOC_DEBUG]: #define MALLOC_DEBUG
to zero if it is not defined elsewhere. (mtrim): Test
the value of MALLOC_DEBUG with #if rather than #ifdef.
Objections were raised surrounding the calloc simplification
and it is better to revert the patch, continue discussions
and then submit a new patch for inclusion with all issues
fully addressed.
To make future improvements of allocator simpler we could for now calloc
just call malloc and memset. With that we could omit a changes that
would duplicate malloc changes anyway.
Perform sanity check only if we have_lock. Due to lockless nature of fastbins
we need to be careful derefencing pointers to fastbin entries (chunksize(old)
in this case) in multithreaded environments.
The fix is to add have_lock to the if-condition checks. The rest of the patch
only makes code more readable.
* malloc/malloc.c (_int_free): Perform sanity check only if we
have_lock.
A very large alignment argument passed to mealign/posix_memalign
causes _int_memalign to enter an infinite loop. Limit the maximum
alignment value to the maximum representable power of two to
prevent this from happening.
Changelog:
2013-10-30 Will Newton <will.newton@linaro.org>
[BZ #16038]
* malloc/hooks.c (memalign_check): Limit alignment to the
maximum representable power of two.
* malloc/malloc.c (__libc_memalign): Likewise.
* malloc/tst-memalign.c (do_test): Add test for very
large alignment values.
* malloc/tst-posix_memalign.c (do_test): Likewise.
for ChangeLog
* malloc/arena.c (new_heap): New memory_heap_new probe.
(grow_heap): New memory_heap_more probe.
(shrink_heap): New memory_heap_less probe.
(heap_trim): New memory_heap_free probe.
* malloc/malloc.c (sysmalloc): New memory_sbrk_more probe.
(systrim): New memory_sbrk_less probe.
* manual/probes.texi: Document them.
A large bytes parameter to memalign could cause an integer overflow
and corrupt allocator internals. Check the overflow does not occur
before continuing with the allocation.
ChangeLog:
2013-09-11 Will Newton <will.newton@linaro.org>
[BZ #15857]
* malloc/malloc.c (__libc_memalign): Check the value of bytes
does not overflow.
A large bytes parameter to valloc could cause an integer overflow
and corrupt allocator internals. Check the overflow does not occur
before continuing with the allocation.
ChangeLog:
2013-09-11 Will Newton <will.newton@linaro.org>
[BZ #15856]
* malloc/malloc.c (__libc_valloc): Check the value of bytes
does not overflow.
A large bytes parameter to pvalloc could cause an integer overflow
and corrupt allocator internals. Check the overflow does not occur
before continuing with the allocation.
ChangeLog:
2013-09-11 Will Newton <will.newton@linaro.org>
[BZ #15855]
* malloc/malloc.c (__libc_pvalloc): Check the value of bytes
does not overflow.
Introduce (only on Linux) and use a HAVE_MREMAP symbol to advertize mremap
availability.
Move the malloc-sysdep.h include from arena.c to malloc.c, since what is
provided by malloc-sysdep.h is needed earlier in malloc.c, before the inclusion
of arena.c.
[BZ #1349]
malloc_usable_size returns the usable size in an allocated chunk,
which may be >= the requested size. In the case of MALLOC_CHECK_ being
exported to > 0 however, only the requested size is usable, since a
magic value is written at the end of the request size to trap writes
beyond request bounds. Hence, when MALLOC_CHECK_ is exported to > 0,
malloc_usable_size() should return the request size.
* malloc.c/arena.c (reused_arena): New parameter, avoid_arena.
When avoid_arena is set, don't retry in the that arena. Pick the
next one, whatever it might be.
(arena_get2): New parameter avoid_arena, pass through to reused_arena.
(arena_lock): Pass in new parameter to arena_get2.
* malloc/malloc.c (__libc_memalign): Pass in new parameter to
arena_get2.
(__libc_malloc): Unify retrying after main arena failure with
__libc_memalign version.
(__libc_valloc, __libc_pvalloc, __libc_calloc): Likewise.
With atomic fastbins the checks performed can race with concurrent
modifications of the arena. If we detect a problem re-do the test
after getting the lock.
The following patch fixes catomic_compare_and_exchange_*_rel definitions
(which were never used and weren't correct) and uses
catomic_compare_and_exchange_val_rel in _int_free. Comparing to the
pre-2009-07-02 --enable-experimental-malloc state the generated code should
be identical on all arches other than ppc/ppc64 and on ppc/ppc64 should use
lwsync instead of isync barrier.
2009-04-16 Ulrich Drepper <drepper@redhat.com>
[BZ #9957]
* malloc/malloc.c (force_reg): Define.
(sYSMALLOc): Load hook variable into variable
before test and force into register.
(sYSTRIm): Likewise.
(public_mALLOc): Force hook value into register.
(public_fREe): Likewise.
(public_rEALLOc): Likewise.
(public_mEMALIGn): Likewise.
(public_vALLOc): Likewise.
(public_pVALLOc): Likewise.
(public_cALLOc): Likewise.
(__posix_memalign): Likewise.
* malloc/arena.c (ptmalloc_init): Load hook variable into variable
before test and force into register.
* malloc/hooks.c (top_check): Likewise.
(public_s_ET_STATe): Pretty printing.
* resolv/res_send.c (send_dg): Don't just ignore the result we got
in case we only receive one reply in single-request mode.
Change all callers.
(_int_realloc): Likewise.
All _int_* functions are now static.
* malloc/hooks.c: Change all callers to _int_free and _int_realloc.
* malloc/arena.c: Likewise.
* include/malloc.h: Remove now unnecessary declarations of the _int_*
functions.
mTRIm for all of them.
(mTRIm): Additionally iterate over all free blocks and use madvise
to free memory for all those blocks which contain at least one
memory page.
* malloc/malloc.c (do_check_malloc_state): Minimal cleanups.
(public_sET_STATe): If ms->version < 3, put all chunks into
unsorted chunks and clear {fd,bk}_nextsize fields of largebin
chunks.
* malloc/malloc.c [MALLOC_DEBUG]: Revert 2007-05-13 changes.
* malloc/hooks.c: Likewise.
* malloc/arena.c: Likewise.
* malloc/malloc.c (do_check_malloc_state): Don't assert
n_mmaps is not greater than n_mmaps_max. This removes the need
for the previous change.
* malloc/Makefile (CFLAGS-malloc.c): Revert accidental
2007-05-07 commit.
2007-04-30 Ulrich Drepper <drepper@redhat.com>
Jakub Jelinek <jakub@redhat.com>
[BZ #4349]
* malloc/malloc.c: Keep separate list for first blocks on the bin
lists with a given size. This helps skipping over list elements
we know won't fit in two places.
Inspired by a patch by Tomash Brechko <tomash.brechko@gmail.com>.
2006-10-17 Jakub Jelinek <jakub@redhat.com>
* sunrpc/xdr_mem.c (xdrmem_setpos): Don't compare addresses
as signed longs, check for x_base + pos overflow.
* sunrpc/Makefile (tests): Add tst-xdrmem2.
* sunrpc/tst-xdrmem2.c: New test.
2006-10-18 Ulrich Drepper <drepper@redhat.com>
* elf/dl-lookup.c (_dl_lookup_symbol_x): Add warning to
_dl_lookup_symbol_x code.
2006-10-17 Jakub Jelinek <jakub@redhat.com>
* elf/dl-runtime.c: Include sysdep-cancel.h.
(_dl_fixup, _dl_profile_fixup): Use __rtld_mrlock_* and
scoperec->nusers only if !SINGLE_THREAD_P. Use atomic_*
instead of catomic_* macros.
* elf/dl-sym.c: Include sysdep-cancel.h.
(do_sym): Use __rtld_mrlock_* and scoperec->nusers only
if !SINGLE_THREAD_P. Use atomic_* instead of catomic_* macros.
* elf/dl-close.c: Include sysdep-cancel.h.
(_dl_close): Use __rtld_mrlock_* and scoperec->nusers only
if !SINGLE_THREAD_P. Use atomic_* instead of catomic_* macros.
* elf/dl-open.c: Include sysdep-cancel.h.
(dl_open_worker): Use __rtld_mrlock_* and scoperec->nusers only
if !SINGLE_THREAD_P. Use atomic_* instead of catomic_* macros.
2006-10-17 Jakub Jelinek <jakub@redhat.com>
[BZ #3313]
* malloc/malloc.c (malloc_consolidate): Set maxfb to address of last
fastbin rather than end of fastbin array.
2006-10-18 Ulrich Drepper <drepper@redhat.com>
* sysdeps/i386/i486/bits/atomic.h (catomic_decrement): Use correct
body macro.
* sysdeps/x86_64/bits/atomic.h
(__arch_c_compare_and_exchange_val_64_acq): Add missing casts.
(catomic_decrement): Use correct body macro.
2006-10-17 Jakub Jelinek <jakub@redhat.com>
* include/atomic.h: Add a unique prefix to all local variables
in macros.
* csu/tst-atomic.c (do_test): Test also catomic_* macros.
* include/link.h: Include <rtld-lowlevel.h>. Define struct
* malloc/malloc.c (malloc_consolidate): Don't use get_fast_max to
determine highest fast bin to consolidate, always look into all of
them.
(do_check_malloc_state): Only require for empty bins for large
sizes in main arena.
* malloc/malloc.c (sYSMALLOc): Only call grow_heap if
(long) (MINSIZE + nb - old_size) is positive.
* malloc/arena.c (grow_heap): When growing bail even if new_size
is negative.
ld.so.
* malloc/malloc.c (_int_malloc): Use full list insert and not
shortcut which assumes the list is empty for large requests
too.
* elf/tst-addr1.c (do_test): Allow i.dli_sname "_IO_printf".
2006-08-27 Ulrich Drepper <drepper@redhat.com>
[BZ #2684]
* malloc/malloc.c (public_rEALLOc): Try harder by using other
arenas if allocation failed.
Patch mostly by Jan Edler <jan.edler@indexengines.com>.
waste bins[0..1].
(malloc_state): Reduce bins size by 2.
(_int_malloc): Fix test for large enough buffer for early termination.
When no unsorted block matches perfectly and an exiting block has
to be split, use full list insert and not shortcut which assumes
the list is empty.
platforms define as 1MB. For 64-bit platforms as 32MB. The lower
limit is needed to avoid the exploding of the address space
requirement for secondary heaps.
* malloc/arena.c (HEAP_MAX_SIZE): Define using
DEFAULT_MMAP_THRESHOLD_MAX if it is defined.
* sysdeps/mach/hurd/fchmodat.c: New file.
* sysdeps/mach/hurd/fchownat.c: New file.
* sysdeps/mach/hurd/fxstatat.c: New file.
* sysdeps/mach/hurd/fxstatat64.c: New file.
* sysdeps/mach/hurd/linkat.c: New file.
* sysdeps/mach/hurd/mkdirat.c: New file.
* sysdeps/mach/hurd/openat.c: New file.
* sysdeps/mach/hurd/openat64.c: New file.
* sysdeps/mach/hurd/symlinkat.c: New file.
* sysdeps/mach/hurd/unlinkat.c: New file.
* sysdeps/mach/hurd/xmknod.c (__xmknod): Just call __xmknodat.
Guts move to ...
* sysdeps/mach/hurd/xmknodat.c: ... here, new file.
* hurd/lookup-at.c: New file.
* hurd/Makefile (routines): Add it.
* hurd/hurd/fd.h: Declare __file_name_lookup_at,
__file_name_split_at and __directory_name_split_at.
* hurd/hurd/lookup.h: Declare {,__}hurd_directory_name_split.
* hurd/hurdlookup.c (__hurd_directory_name_split): Use __memrchr
unconditionally.
* sysdeps/mach/hurd/open.c: Define {,__,__libc_,}open64 as aliases.
* sysdeps/mach/hurd/open64.c: New file.
The correct value differs only on powerpc32, and for now changing it
there is causing more trouble than it's worth.
* malloc/arena.c: Add compile-time sanity check on padding calculation.
2006-03-05 Jakub Jelinek <jakub@redhat.com>
* malloc/arena.c (heap_info): Adjust the padding size if
MALLOC_ALIGNMENT > 2 * SIZE_SZ.
