[PATCH] Fix possible memory corruption in xfs_readlink

[Carlos Maiolino]

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 at redhat.com>
---
 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..9ca6676 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_emerg(mp, "%s: inode (%lld) 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