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From: Ben Myers <bpm@sgi.com>
To: greg@kroah.com, stable@vger.kernel.org
Cc: bpm@sgi.com, Alex Elder <aelder@sgi.com>,
	Carlos Maiolino <cmaiolino@redhat.com>,
	xfs@oss.sgi.com
Subject: [PATCH 5/6] xfs: Fix possible memory corruption in xfs_readlink
Date: Wed, 30 Nov 2011 12:10:59 -0600	[thread overview]
Message-ID: <1322676660-22945-6-git-send-email-bpm@sgi.com> (raw)
In-Reply-To: <1322676660-22945-1-git-send-email-bpm@sgi.com>

From: Carlos Maiolino <cmaiolino@redhat.com>

commit b52a360b2aa1c59ba9970fb0f52bbb093fcc7a24 upstream.

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>
---
 fs/xfs/xfs_vnodeops.c |   14 ++++++++++----
 1 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/fs/xfs/xfs_vnodeops.c b/fs/xfs/xfs_vnodeops.c
index 51fc429..b9e2873 100644
--- a/fs/xfs/xfs_vnodeops.c
+++ b/fs/xfs/xfs_vnodeops.c
@@ -113,7 +113,7 @@ xfs_readlink(
 	char		*link)
 {
 	xfs_mount_t	*mp = ip->i_mount;
-	int		pathlen;
+	xfs_fsize_t	pathlen;
 	int		error = 0;
 
 	trace_xfs_readlink(ip);
@@ -123,13 +123,19 @@ 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';
-- 
1.7.8.rc0.46.g5ae0f

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  parent reply	other threads:[~2011-11-30 17:58 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-11-23 21:38 [PATCH 0/6] XFS update for 3.1-stable Ben Myers
2011-11-23 21:38 ` [PATCH 1/6] xfs: don't serialise direct IO reads on page cache checks Ben Myers
2011-11-23 21:38 ` [PATCH 2/6] xfs: avoid direct I/O write vs buffered I/O race Ben Myers
2011-11-23 21:38 ` [PATCH 3/6] xfs: Return -EIO when xfs_vn_getattr() failed Ben Myers
2011-11-23 21:38 ` [PATCH 4/6] xfs: fix buffer flushing during unmount Ben Myers
2011-11-23 21:38 ` [PATCH 5/6] xfs: Fix possible memory corruption in xfs_readlink Ben Myers
2011-11-23 21:38 ` [PATCH 6/6] xfs: use doalloc flag in xfs_qm_dqattach_one() Ben Myers
2011-11-28 11:00 ` [PATCH 0/6] XFS update for 3.1-stable Christoph Hellwig
2011-11-28 13:48   ` Greg KH
2011-11-28 16:54     ` Ben Myers
2011-11-28 21:40       ` Greg KH
2011-11-30 18:10         ` XFS update for 3.1-stable (resent) Ben Myers
2011-11-30 18:10           ` [PATCH 1/6] xfs: don't serialise direct IO reads on page cache checks Ben Myers
2011-11-30 18:10           ` [PATCH 2/6] xfs: avoid direct I/O write vs buffered I/O race Ben Myers
2011-11-30 18:10           ` [PATCH 3/6] xfs: Return -EIO when xfs_vn_getattr() failed Ben Myers
2011-11-30 18:10           ` [PATCH 4/6] xfs: fix buffer flushing during unmount Ben Myers
2011-11-30 18:10           ` Ben Myers [this message]
2011-11-30 18:11           ` [PATCH 6/6] xfs: use doalloc flag in xfs_qm_dqattach_one() Ben Myers
  -- strict thread matches above, loose matches on Subject: below --
2011-12-01 23:27 [PATCH 0/6] XFS update for 3.1-stable (again) Ben Myers
2011-12-01 23:27 ` [PATCH 5/6] xfs: Fix possible memory corruption in xfs_readlink Ben Myers

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