[Bug libc/18093] New: Corrupted aux-cache causes ldconfig to segfault

[Bug libc/18093] New: Corrupted aux-cache causes ldconfig to segfault

[aurelien at aurel32 dot net]

https://sourceware.org/bugzilla/show_bug.cgi?id=18093

            Bug ID: 18093
           Summary: Corrupted aux-cache causes ldconfig to segfault
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
          Assignee: unassigned at sourceware dot org
          Reporter: aurelien at aurel32 dot net
                CC: drepper.fsp at gmail dot com

ldconfig is using an aux-cache to speed up the ld.so.cache update. It is read
by mmaping the file to a structure which contains data offsets used as
pointers. As they are not checked, it is not hard to get ldconfig to segfault
with a corrupted file. This happens for instance if the file is truncated,
which is common following a filesystem check after system crash.

This can be reproduced for example by truncating the file to roughly half of
it's size.

There is already in some code in elf/cache.c (load_aux_cache) to check for a
corrupted aux cache, but it happens not to be enough.

Patch to fix that will follow on the mailing list.

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[Bug libc/18093] Corrupted aux-cache causes ldconfig to segfault

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=18093

--- Comment #1 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
This is an automated email from the git hooks/post-receive script. It was
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the project "GNU C Library master sources".

The branch, master has been updated
       via  6a1cf708dd5681b517744d6d4fac02e4e4a0aa2e (commit)
      from  a2d4cf72c0ab07d4e58b42c01ac3ed2b95ca8d9b (commit)

Those revisions listed above that are new to this repository have
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- Log -----------------------------------------------------------------
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=6a1cf708dd5681b517744d6d4fac02e4e4a0aa2e

commit 6a1cf708dd5681b517744d6d4fac02e4e4a0aa2e
Author: Aurelien Jarno <aurelien@aurel32.net>
Date:   Wed Mar 11 21:03:50 2015 -0400

    Fix ldconfig segmentation fault with corrupted cache (Bug 18093).

    ldconfig is using an aux-cache to speed up the ld.so.cache update. It
    is read by mmaping the file to a structure which contains data offsets
    used as pointers. As they are not checked, it is not hard to get
    ldconfig to segfault with a corrupted file. This happens for instance if
    the file is truncated, which is common following a filesystem check
    following a system crash.

    This can be reproduced for example by truncating the file to roughly
    half of it's size.

    There is already some code in elf/cache.c (load_aux_cache) to check
    for a corrupted aux cache, but it happens to be broken and not enough.
    The test (aux_cache->nlibs >= aux_cache_size) compares the number of
    libs entry with the cache size. It's a non sense, as it basically
    assumes that each library entry is a 1 byte... Instead this commit
    computes the theoretical cache size using the headers and compares it
    to the real size.

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

Summary of changes:
 ChangeLog   |    6 ++++++
 NEWS        |    2 +-
 elf/cache.c |    4 +++-
 3 files changed, 10 insertions(+), 2 deletions(-)

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[Bug libc/18093] Corrupted aux-cache causes ldconfig to segfault

[aurelien at aurel32 dot net]

https://sourceware.org/bugzilla/show_bug.cgi?id=18093

Aurelien Jarno <aurelien at aurel32 dot net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #2 from Aurelien Jarno <aurelien at aurel32 dot net> ---
Fixed in master.

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