[PATCH 5.17 187/219] cifs: verify that tcon is valid before dereference in cifs_kill_sb

Greg Kroah-Hartman
2022-04-18T12:37:20Z

From: Ronnie Sahlberg <lsahlber@redhat.com>

commit 8b6c58458ee3206dde345fce327a4cb83e69caf9 upstream.

On umount, cifs_sb->tlink_tree might contain entries that do not represent
a valid tcon.
Check the tcon for error before we dereference it.

Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Cc: stable@vger.kernel.org
Reviewed-by: Shyam Prasad N <sprasad@microsoft.com>
Reported-by: Xiaoli Feng <xifeng@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/cifs/cifsfs.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -266,10 +266,11 @@ static void cifs_kill_sb(struct super_bl
* before we kill the sb.
*/
if (cifs_sb->root) {
- node = rb_first(root);
- while (node != NULL) {
+ for (node = rb_first(root); node; node = rb_next(node)) {
tlink = rb_entry(node, struct tcon_link, tl_rbnode);
tcon = tlink_tcon(tlink);
+ if (IS_ERR(tcon))
+ continue;
cfid = &tcon->crfid;
mutex_lock(&cfid->fid_mutex);
if (cfid->dentry) {
@@ -277,7 +278,6 @@ static void cifs_kill_sb(struct super_bl
cfid->dentry = NULL;
}
mutex_unlock(&cfid->fid_mutex);
- node = rb_next(node);
}

/* finally release root dentry */