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authorShyam Prasad N <sprasad@microsoft.com>2023-11-14 07:58:23 +0300
committerSteve French <stfrench@microsoft.com>2023-11-14 20:39:35 +0300
commit5eef12c4e3230f2025dc46ad8c4a3bc19978e5d7 (patch)
tree65c5e067176016ff515419542b41b47c1bbc6044 /fs/smb/client
parent29954d5b1e0d67a4cd61c30c2201030c97e94b1e (diff)
downloadlinux-5eef12c4e3230f2025dc46ad8c4a3bc19978e5d7.tar.xz
cifs: fix lock ordering while disabling multichannel
The code to handle the case of server disabling multichannel was picking iface_lock with chan_lock held. This goes against the lock ordering rules, as iface_lock is a higher order lock (even if it isn't so obvious). This change fixes the lock ordering by doing the following in that order for each secondary channel: 1. store iface and server pointers in local variable 2. remove references to iface and server in channels 3. unlock chan_lock 4. lock iface_lock 5. dec ref count for iface 6. unlock iface_lock 7. dec ref count for server 8. lock chan_lock again Since this function can only be called in smb2_reconnect, and that cannot be called by two parallel processes, we should not have races due to dropping chan_lock between steps 3 and 8. Fixes: ee1d21794e55 ("cifs: handle when server stops supporting multichannel") Reported-by: Paulo Alcantara <pc@manguebit.com> Signed-off-by: Shyam Prasad N <sprasad@microsoft.com> Signed-off-by: Steve French <stfrench@microsoft.com>
Diffstat (limited to 'fs/smb/client')
-rw-r--r--fs/smb/client/sess.c22
1 files changed, 13 insertions, 9 deletions
diff --git a/fs/smb/client/sess.c b/fs/smb/client/sess.c
index 0bb2ac929061..8b2d7c1ca428 100644
--- a/fs/smb/client/sess.c
+++ b/fs/smb/client/sess.c
@@ -322,28 +322,32 @@ cifs_disable_secondary_channels(struct cifs_ses *ses)
iface = ses->chans[i].iface;
server = ses->chans[i].server;
+ /*
+ * remove these references first, since we need to unlock
+ * the chan_lock here, since iface_lock is a higher lock
+ */
+ ses->chans[i].iface = NULL;
+ ses->chans[i].server = NULL;
+ spin_unlock(&ses->chan_lock);
+
if (iface) {
spin_lock(&ses->iface_lock);
kref_put(&iface->refcount, release_iface);
- ses->chans[i].iface = NULL;
iface->num_channels--;
if (iface->weight_fulfilled)
iface->weight_fulfilled--;
spin_unlock(&ses->iface_lock);
}
- spin_unlock(&ses->chan_lock);
- if (server && !server->terminate) {
- server->terminate = true;
- cifs_signal_cifsd_for_reconnect(server, false);
- }
- spin_lock(&ses->chan_lock);
-
if (server) {
- ses->chans[i].server = NULL;
+ if (!server->terminate) {
+ server->terminate = true;
+ cifs_signal_cifsd_for_reconnect(server, false);
+ }
cifs_put_tcp_session(server, false);
}
+ spin_lock(&ses->chan_lock);
}
done: