cifs: fix reference leak for tlink

Don't leak a reference to tlink during the NOTIFY ioctl

Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
CC: Stable <stable@vger.kernel.org> # v5.6+

diff --git a/fs/cifs/ioctl.c b/fs/cifs/ioctl.c
index 4a73e63..dcde44f 100644 (file)
--- a/fs/cifs/ioctl.c
+++ b/fs/cifs/ioctl.c
@@ -169,6 +169,7 @@ long cifs_ioctl(struct file *filep, unsigned int command, unsigned long arg)
        unsigned int xid;
        struct cifsFileInfo *pSMBFile = filep->private_data;
        struct cifs_tcon *tcon;
+       struct tcon_link *tlink;
        struct cifs_sb_info *cifs_sb;
        __u64   ExtAttrBits = 0;
        __u64   caps;
@@ -307,13 +308,19 @@ long cifs_ioctl(struct file *filep, unsigned int command, unsigned long arg)
                                break;
                        }
                        cifs_sb = CIFS_SB(inode->i_sb);
-                       tcon = tlink_tcon(cifs_sb_tlink(cifs_sb));
+                       tlink = cifs_sb_tlink(cifs_sb);
+                       if (IS_ERR(tlink)) {
+                               rc = PTR_ERR(tlink);
+                               break;
+                       }
+                       tcon = tlink_tcon(tlink);
                        if (tcon && tcon->ses->server->ops->notify) {
                                rc = tcon->ses->server->ops->notify(xid,
                                                filep, (void __user *)arg);
                                cifs_dbg(FYI, "ioctl notify rc %d\n", rc);
                        } else
                                rc = -EOPNOTSUPP;
+                       cifs_put_tlink(tlink);
                        break;
                default:
                        cifs_dbg(FYI, "unsupported ioctl\n");