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[Bug malloc/16159] malloc_printerr() deadlock, when calling malloc_printerr() again


https://sourceware.org/bugzilla/show_bug.cgi?id=16159

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https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=fff94fa2245612191123a8015eac94eb04f001e2

commit fff94fa2245612191123a8015eac94eb04f001e2
Author: Siddhesh Poyarekar <siddhesh@redhat.com>
Date:   Tue May 19 06:40:37 2015 +0530

    Avoid deadlock in malloc on backtrace (BZ #16159)

    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.

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=99db95db37b4fd95986fadb263e4180b7381d10d

commit 99db95db37b4fd95986fadb263e4180b7381d10d
Author: Siddhesh Poyarekar <siddhesh@redhat.com>
Date:   Tue May 19 06:36:29 2015 +0530

    Succeed if make check does not report any errors

    The conditional that evaluates if there are any FAILed test cases
    currently always fails, since we ensure it fails if we find any
    unexpected results in tests.sum and it would obviously fail if it does
    not find failed results in tests.sum.  This patch fixes this by simply
    inverting the result of the egrep, i.e. succeed if egrep fails (to
    find failed results) and fail if it succeeds.

    Tested with 'make subdirs=localedata check' and 'make subdirs=locale
    check' where all tests succeed and with 'make subdirs=elf check' where
    a couple of tests fail for me.

         * Makefile (summarize-tests): Fix return value on success.

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=920d70128baa41ce6ce3b1b4771fe912f8d1691a

commit 920d70128baa41ce6ce3b1b4771fe912f8d1691a
Author: Siddhesh Poyarekar <siddhesh@redhat.com>
Date:   Tue May 19 06:35:37 2015 +0530

    Add envz_remove to the libc manual

    I was told that Ma Shimao submitted a patch to add envz_remove to the
    libc manual, but the patch could not be accepted since he does not
    have a copyright assignment in place.  I have been woefully behind on
    libc-alpha recently and have not seen the patch or the discussion
    thread.  I have also not read the man page for envz_remove, so
    Alexandre Oliva asked me if I could write this independently and post
    a patch.  The patch below is the result of the same - I have written
    it based on the implementation in string/envz.c and Alex told me via
    email that the function is AS, AC and MT-safe like envz_strip.

    I assume Alex and Carlos cannot review this since they have been
    tainted by the original patch (I haven't even tried to look for a link
    to it since I don't want to be tainted) so someone else will have to
    review this.  If there are no reviewers till the end of the week, I
    will commit this since I believe there is a chance that there are no
    other reviewers who haven't read that thread.

        * manual/string.texi (Envz Functions): Add envz_remove.

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog                                          |   35 ++++
 Makefile                                           |    2 +-
 NEWS                                               |   20 +-
 malloc/Makefile                                    |    6 +-
 malloc/arena.c                                     |   22 ++-
 malloc/hooks.c                                     |   12 +-
 malloc/malloc.c                                    |  173 ++++++++++++--------
 .../tst-detach1.c => malloc/tst-malloc-backtrace.c |   49 +++---
 manual/string.texi                                 |    8 +
 9 files changed, 213 insertions(+), 114 deletions(-)
 copy nptl/tst-detach1.c => malloc/tst-malloc-backtrace.c (57%)

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