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xfs: Fix possible memory corruption in xfs_readlink 

Fixes a possible memory corruption when the link is larger than
MAXPATHLEN and XFS_DEBUG is not enabled. This also remove the
S_ISLNK assert, since the inode mode is checked previously in
xfs_readlink_by_handle() and via VFS.

Updated to address concerns raised by Ben Hutchings about the loose
attention paid to 32- vs 64-bit values, and the lack of handling a
potentially negative pathlen value:
 - Changed type of "pathlen" to be xfs_fsize_t, to match that of
   ip->i_d.di_size
 - Added checking for a negative pathlen to the too-long pathlen
   test, and generalized the message that gets reported in that case
   to reflect the change
As a result, if a negative pathlen were encountered, this function
would return EFSCORRUPTED (and would fail an assertion for a debug
build)--just as would a too-long pathlen.

Signed-off-by: Alex Elder <aelder@sgi.com>
Signed-off-by: Carlos Maiolino <cmaiolino@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Carlos Maiolino 2011-11-07 16:10:24 +00:00 committed by Alex Elder
parent 1ea6b8f489
commit b52a360b2a
1 changed files with 10 additions and 4 deletions
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14
fs/xfs/xfs_vnodeops.c
View File

@ -112,7 +112,7 @@ xfs_readlink(
char *link)
{
xfs_mount_t *mp = ip->i_mount;
int pathlen;
xfs_fsize_t pathlen;
int error = 0;
trace_xfs_readlink(ip);
@ -122,13 +122,19 @@ xfs_readlink(
xfs_ilock(ip, XFS_ILOCK_SHARED);
ASSERT(S_ISLNK(ip->i_d.di_mode));
ASSERT(ip->i_d.di_size <= MAXPATHLEN);
pathlen = ip->i_d.di_size;
if (!pathlen)
goto out;
if (pathlen < 0 || pathlen > MAXPATHLEN) {
xfs_alert(mp, "%s: inode (%llu) bad symlink length (%lld)",
__func__, (unsigned long long) ip->i_ino,
(long long) pathlen);
ASSERT(0);
return XFS_ERROR(EFSCORRUPTED);
}
if (ip->i_df.if_flags & XFS_IFINLINE) {
memcpy(link, ip->i_df.if_u1.if_data, pathlen);
link[pathlen] = '\0';