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[PATCH] Fix possible memory corruption in xfs_readlink

To: xfs@xxxxxxxxxxx
Subject: [PATCH] Fix possible memory corruption in xfs_readlink
From: Carlos Maiolino <cmaiolino@xxxxxxxxxx>
Date: Tue, 18 Oct 2011 02:18:58 -0200
Cc: Carlos Maiolino <cmaiolino@xxxxxxxxxx>
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.

Signed-off-by: Carlos Maiolino <cmaiolino@xxxxxxxxxx>
---
 fs/xfs/xfs_vnodeops.c |   11 ++++++++---
 1 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/fs/xfs/xfs_vnodeops.c b/fs/xfs/xfs_vnodeops.c
index 51fc429..c3288be 100644
--- a/fs/xfs/xfs_vnodeops.c
+++ b/fs/xfs/xfs_vnodeops.c
@@ -123,13 +123,18 @@ 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 > MAXPATHLEN) {
+               xfs_alert(mp, "%s: inode (%llu) symlink length (%d) too long",
+                        __func__, (unsigned long long)ip->i_ino, 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';
-- 
1.7.6.2

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