6.6-stable review patch. If anyone has any objections, please let me know.
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From: Shyam Prasad N sprasad@microsoft.com
[ Upstream commit ee36a3b345c433a846effcdcfba437c2298eeda5 ]
Following a successful cifs_tree_connect, we have the code to scale up/down the number of channels in the session. However, it is not protected by a lock today.
As a result, this code can be executed by several processes that select the same channel. The core functions handle this well, as they pick chan_lock. However, we've seen cases where smb2_reconnect throws some warnings.
To fix that, this change introduces a flags bitmap inside the cifs_ses structure. A new flag type is used to ensure that only one process enters this section at any time.
Signed-off-by: Shyam Prasad N sprasad@microsoft.com Signed-off-by: Steve French stfrench@microsoft.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/smb/client/cifsglob.h | 3 +++ fs/smb/client/smb2pdu.c | 18 +++++++++++++++++- 2 files changed, 20 insertions(+), 1 deletion(-)
diff --git a/fs/smb/client/cifsglob.h b/fs/smb/client/cifsglob.h index f794b16095e43..dcc41fe33b705 100644 --- a/fs/smb/client/cifsglob.h +++ b/fs/smb/client/cifsglob.h @@ -1018,6 +1018,8 @@ struct cifs_chan { __u8 signkey[SMB3_SIGN_KEY_SIZE]; };
+#define CIFS_SES_FLAG_SCALE_CHANNELS (0x1) + /* * Session structure. One of these for each uid session with a particular host */ @@ -1050,6 +1052,7 @@ struct cifs_ses { enum securityEnum sectype; /* what security flavor was specified? */ bool sign; /* is signing required? */ bool domainAuto:1; + unsigned int flags; __u16 session_flags; __u8 smb3signingkey[SMB3_SIGN_KEY_SIZE]; __u8 smb3encryptionkey[SMB3_ENC_DEC_KEY_SIZE]; diff --git a/fs/smb/client/smb2pdu.c b/fs/smb/client/smb2pdu.c index 5d9c87d2e1e01..ce2d28537bc8a 100644 --- a/fs/smb/client/smb2pdu.c +++ b/fs/smb/client/smb2pdu.c @@ -399,6 +399,15 @@ smb2_reconnect(__le16 smb2_command, struct cifs_tcon *tcon, goto out; }
+ spin_lock(&ses->ses_lock); + if (ses->flags & CIFS_SES_FLAG_SCALE_CHANNELS) { + spin_unlock(&ses->ses_lock); + mutex_unlock(&ses->session_mutex); + goto skip_add_channels; + } + ses->flags |= CIFS_SES_FLAG_SCALE_CHANNELS; + spin_unlock(&ses->ses_lock); + if (!rc && (server->capabilities & SMB2_GLOBAL_CAP_MULTI_CHANNEL)) { mutex_unlock(&ses->session_mutex); @@ -428,15 +437,22 @@ smb2_reconnect(__le16 smb2_command, struct cifs_tcon *tcon, if (ses->chan_max > ses->chan_count && ses->iface_count && !SERVER_IS_CHAN(server)) { - if (ses->chan_count == 1) + if (ses->chan_count == 1) { cifs_server_dbg(VFS, "supports multichannel now\n"); + queue_delayed_work(cifsiod_wq, &tcon->query_interfaces, + (SMB_INTERFACE_POLL_INTERVAL * HZ)); + }
cifs_try_adding_channels(ses); } } else { mutex_unlock(&ses->session_mutex); } + skip_add_channels: + spin_lock(&ses->ses_lock); + ses->flags &= ~CIFS_SES_FLAG_SCALE_CHANNELS; + spin_unlock(&ses->ses_lock);
if (smb2_command != SMB2_INTERNAL_CMD) mod_delayed_work(cifsiod_wq, &server->reconnect, 0);