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cifs: avoid race during socket reconnect between send and recv

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When a TCP connection gets reestablished by the sender in cifs_reconnect,
There is a chance for race condition with demultiplex thread waiting in
cifs_readv_from_socket on the old socket. It will now return -ECONNRESET.

This condition is handled by comparing socket pointer before and after
sock_recvmsg. If the socket pointer has changed, we should not call
cifs_reconnect again, but instead retry with new socket.

Also fixed another bug in my prev mchan commits.
We should always reestablish session (even if binding) on a channel
that needs reconnection.

Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
This commit is contained in:
Shyam Prasad N
2021-10-25 05:44:10 +00:00
committed by Steve French
parent 73f9bfbe3d
commit bda487ac4b
3 changed files with 6 additions and 24 deletions
Download Patch File Download Diff File Expand all files Collapse all files

14
fs/cifs/connect.c
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@@ -172,12 +172,11 @@ static void
cifs_mark_tcp_ses_conns_for_reconnect(struct TCP_Server_Info *server,
bool mark_smb_session)
{
unsigned int num_sessions = 0;
struct TCP_Server_Info *pserver;
struct cifs_ses *ses;
struct cifs_tcon *tcon;
struct mid_q_entry *mid, *nmid;
struct list_head retry_list;
struct TCP_Server_Info *pserver;
server->maxBuf = 0;
server->max_read = 0;
@@ -199,17 +198,13 @@ cifs_mark_tcp_ses_conns_for_reconnect(struct TCP_Server_Info *server,
if (!mark_smb_session && cifs_chan_needs_reconnect(ses, server))
goto next_session;
if (mark_smb_session)
CIFS_SET_ALL_CHANS_NEED_RECONNECT(ses);
else
cifs_chan_set_need_reconnect(ses, server);
cifs_chan_set_need_reconnect(ses, server);
/* If all channels need reconnect, then tcon needs reconnect */
if (!mark_smb_session && !CIFS_ALL_CHANS_NEED_RECONNECT(ses))
goto next_session;
ses->status = CifsNeedReconnect;
num_sessions++;
list_for_each_entry(tcon, &ses->tcon_list, tcon_list) {
tcon->need_reconnect = true;
@@ -223,16 +218,13 @@ next_session:
}
spin_unlock(&cifs_tcp_ses_lock);
if (num_sessions == 0)
return;
/*
* before reconnecting the tcp session, mark the smb session (uid)
* and the tid bad so they are not used until reconnected
*/
cifs_dbg(FYI, "%s: marking sessions and tcons for reconnect\n",
cifs_dbg(FYI, "%s: marking sessions and tcons for reconnect and tearing down socket\n",
__func__);
/* do not want to be sending data on a socket we are freeing */
cifs_dbg(FYI, "%s: tearing down socket\n", __func__);
mutex_lock(&server->srv_mutex);
if (server->ssocket) {
cifs_dbg(FYI, "State: 0x%x Flags: 0x%lx\n", server->ssocket->state,