Commit b52a360b authored Nov 07, 2011 by Carlos Maiolino Committed by Alex Elder Nov 08, 2011

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>

parent 1ea6b8f4

fs/xfs/xfs_vnodeops.c

+10 −4

Original line number	Diff line number	Diff line
		@@ -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';