diff options
| author | Shyam Prasad N <sprasad@microsoft.com> | 2021-07-19 10:54:46 +0000 |
|---|---|---|
| committer | Steve French <stfrench@microsoft.com> | 2021-11-12 16:22:20 -0600 |
| commit | 724244cdb3828522109c88e56a0242537aefabe9 (patch) | |
| tree | 59f14fbd73adcbb3b89fc822d24b99f47883ea67 /fs/cifs/connect.c | |
| parent | 8e07757bece6e81b0b0910358ebceca3032bc6c7 (diff) | |
cifs: protect session channel fields with chan_lock
Introducing a new spin lock to protect all the channel related
fields in a cifs_ses struct. This lock should be taken
whenever dealing with the channel fields, and should be held
only for very short intervals which will not sleep.
Currently, all channel related fields in cifs_ses structure
are protected by session_mutex. However, this mutex is held for
long periods (sometimes while waiting for a reply from server).
This makes the codepath quite tricky to change.
Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
Reviewed-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: Steve French <stfrench@microsoft.com>
Diffstat (limited to 'fs/cifs/connect.c')
| -rw-r--r-- | fs/cifs/connect.c | 25 |
1 files changed, 22 insertions, 3 deletions
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c index 498ec05ca10d..09a532ed8fe4 100644 --- a/fs/cifs/connect.c +++ b/fs/cifs/connect.c @@ -1577,8 +1577,12 @@ static int match_session(struct cifs_ses *ses, struct smb3_fs_context *ctx) * If an existing session is limited to less channels than * requested, it should not be reused */ - if (ses->chan_max < ctx->max_channels) + spin_lock(&ses->chan_lock); + if (ses->chan_max < ctx->max_channels) { + spin_unlock(&ses->chan_lock); return 0; + } + spin_unlock(&ses->chan_lock); switch (ses->sectype) { case Kerberos: @@ -1713,6 +1717,7 @@ cifs_find_smb_ses(struct TCP_Server_Info *server, struct smb3_fs_context *ctx) void cifs_put_smb_ses(struct cifs_ses *ses) { unsigned int rc, xid; + unsigned int chan_count; struct TCP_Server_Info *server = ses->server; cifs_dbg(FYI, "%s: ses_count=%d\n", __func__, ses->ses_count); @@ -1754,12 +1759,24 @@ void cifs_put_smb_ses(struct cifs_ses *ses) list_del_init(&ses->smb_ses_list); spin_unlock(&cifs_tcp_ses_lock); + spin_lock(&ses->chan_lock); + chan_count = ses->chan_count; + spin_unlock(&ses->chan_lock); + /* close any extra channels */ - if (ses->chan_count > 1) { + if (chan_count > 1) { int i; - for (i = 1; i < ses->chan_count; i++) + for (i = 1; i < chan_count; i++) { + /* + * note: for now, we're okay accessing ses->chans + * without chan_lock. But when chans can go away, we'll + * need to introduce ref counting to make sure that chan + * is not freed from under us. + */ cifs_put_tcp_session(ses->chans[i].server, 0); + ses->chans[i].server = NULL; + } } sesInfoFree(ses); @@ -2018,9 +2035,11 @@ cifs_get_smb_ses(struct TCP_Server_Info *server, struct smb3_fs_context *ctx) mutex_lock(&ses->session_mutex); /* add server as first channel */ + spin_lock(&ses->chan_lock); ses->chans[0].server = server; ses->chan_count = 1; ses->chan_max = ctx->multichannel ? ctx->max_channels:1; + spin_unlock(&ses->chan_lock); rc = cifs_negotiate_protocol(xid, ses); if (!rc) |