diff options
| author | Shyam Prasad N <sprasad@microsoft.com> | 2023-11-14 04:58:23 +0000 |
|---|---|---|
| committer | Steve French <stfrench@microsoft.com> | 2023-11-14 11:39:35 -0600 |
| commit | 5eef12c4e3230f2025dc46ad8c4a3bc19978e5d7 (patch) | |
| tree | 65c5e067176016ff515419542b41b47c1bbc6044 | |
| parent | 29954d5b1e0d67a4cd61c30c2201030c97e94b1e (diff) | |
| download | linux-rcu-5eef12c4e3230f2025dc46ad8c4a3bc19978e5d7.tar.gz | |
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>
| -rw-r--r-- | fs/smb/client/sess.c | 22 |
1 files changed, 13 insertions, 9 deletions
diff --git a/fs/smb/client/sess.c b/fs/smb/client/sess.c index 0bb2ac9290617..8b2d7c1ca4284 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: |