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cifs: verify that tcon is valid before dereference in cifs_kill_sb 

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>
This commit is contained in:
Ronnie Sahlberg 2022-04-13 10:02:17 +10:00 committed by Steve French
parent 64c4a37ac0
commit 8b6c58458e
1 changed files with 3 additions and 3 deletions
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6
fs/cifs/cifsfs.c
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@ -266,10 +266,11 @@ static void cifs_kill_sb(struct super_block *sb)
* before we kill the sb. * before we kill the sb.
*/ */
if (cifs_sb->root) { if (cifs_sb->root) {
node = rb_first(root); for (node = rb_first(root); node; node = rb_next(node)) {
while (node != NULL) {
tlink = rb_entry(node, struct tcon_link, tl_rbnode); tlink = rb_entry(node, struct tcon_link, tl_rbnode);
tcon = tlink_tcon(tlink); tcon = tlink_tcon(tlink);
if (IS_ERR(tcon))
continue;
cfid = &tcon->crfid; cfid = &tcon->crfid;
mutex_lock(&cfid->fid_mutex); mutex_lock(&cfid->fid_mutex);
if (cfid->dentry) { if (cfid->dentry) {
@ -277,7 +278,6 @@ static void cifs_kill_sb(struct super_block *sb)
cfid->dentry = NULL; cfid->dentry = NULL;
} }
mutex_unlock(&cfid->fid_mutex); mutex_unlock(&cfid->fid_mutex);
node = rb_next(node);
} }
/* finally release root dentry */ /* finally release root dentry */