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Re: hardlink(1) has buffer overflows, is unsafe on changing trees
From: Solar Designer <solar () openwall com>
Date: Sat, 22 Oct 2011 04:56:21 +0400

On Fri, Oct 21, 2011 at 03:29:41PM +0530, Huzaifa Sidhpurwala wrote:
On 10/20/2011 08:27 PM, Josh Bressers wrote:

The hardlink(1) program from Fedora is susceptible to buffer overflows of
fixed-size nambuf1 and nambuf2 buffers when run on a tree with deeply
nested directories and/or with long directory or file names.  I was able
to reproduce the problem (got a segfault) by running the program on a
directory containing 20 nested directories with 250-character names.

CVE-2011-3630 hardlink buffer overflows
https://bugzilla.redhat.com/show_bug.cgi?id=746709

FORTIFY_SOURCE should really be able to catch this buffer overflow.
The buffer being overflown here in in BSS, But strcat() is used to 
append to this buffer and __builtin___strcat_chk catches it, resulting 
in the program being terminated.

Besides the strcpy() and strcat() with obviously known target buffer
size, there are also:

          strcpy (stpcpy (nambuf2, n2), ".$$$___cleanit___$$$");

and:

      strcpy (p, di->d_name);

where "p" points somewhere inside nambuf1.

These will just need different reproducers.

Alexander


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