ocfs2: Don't walk off the end of fast symlinks.

commit 1fc8a117865b54590acd773a55fbac9221b018f0 upstream.

ocfs2 fast symlinks are NUL terminated strings stored inline in the
inode data area.  However, disk corruption or a local attacker could, in
theory, remove that NUL.  Because we're using strlen() (my fault,
introduced in a731d1 when removing vfs_follow_link()), we could walk off
the end of that string.

Signed-off-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/fs/ocfs2/symlink.c b/fs/ocfs2/symlink.c
index 32499d213fc4f80f37efde6f71196283236896bf..9975457c981f904ca18a512dd7bcbe0f092ac664 100644 (file)
--- a/fs/ocfs2/symlink.c
+++ b/fs/ocfs2/symlink.c
@@ -128,7 +128,7 @@ static void *ocfs2_fast_follow_link(struct dentry *dentry,
        }
 
        /* Fast symlinks can't be large */
-       len = strlen(target);
+       len = strnlen(target, ocfs2_fast_symlink_chars(inode->i_sb));
        link = kzalloc(len + 1, GFP_NOFS);
        if (!link) {
                status = -ENOMEM;