Author: delphij
Date: Wed Dec 10 08:18:22 2014
New Revision: 275665
URL: https://svnweb.freebsd.org/changeset/base/275665
Log:
In r268924 __fflush was modified so that when write(2) was not successful,
_p and _w are adjusted to account for the partial write (if any).
However, _p and _w should not be unconditionally adjusted and should only
be changed when we actually wrote some bytes, or the accumulated accounting
error will eventually result in a heap buffer overflow.
Reported by: adrian and alfred (Norse Corporation)
Security: FreeBSD-SA-14:27.stdio
Security: CVE-2014-8611
Modified:
head/lib/libc/stdio/fflush.c
Modified: head/lib/libc/stdio/fflush.c
==============================================================================
--- head/lib/libc/stdio/fflush.c Wed Dec 10 06:43:16 2014
(r275664)
+++ head/lib/libc/stdio/fflush.c Wed Dec 10 08:18:22 2014
(r275665)
@@ -124,11 +124,13 @@ __sflush(FILE *fp)
t = _swrite(fp, (char *)p, n);
if (t <= 0) {
/* Reset _p and _w. */
- if (p > fp->_p) /* Some was written. */
+ if (p > fp->_p) {
+ /* Some was written. */
memmove(fp->_p, p, n);
- fp->_p += n;
- if ((fp->_flags & (__SLBF | __SNBF)) == 0)
- fp->_w -= n;
+ fp->_p += n;
+ if ((fp->_flags & (__SLBF | __SNBF)) == 0)
+ fp->_w -= n;
+ }
fp->_flags |= __SERR;
return (EOF);
}
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