FAILED: patch "[PATCH] cifs: lock chan_lock outside match_session" failed to apply to 5.15-stable tree

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 2f4e429c846972c8405951a9ff7a82aceeca7461
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '[email protected]' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

2f4e429c8469 ("cifs: lock chan_lock outside match_session")
d7d7a66aacd6 ("cifs: avoid use of global locks for high contention data") 9543c8ab3016 ("cifs: list_for_each() -> list_for_each_entry()") af3a6d1018f0 ("cifs: update cifs_ses::ip_addr after failover")
b54034a73baf ("cifs: during reconnect, update interface if necessary") cc391b694ff0 ("cifs: fix potential deadlock in direct reclaim") 5752bf645f9d ("cifs: avoid parallel session setups on same channel") dd3cd8709ed5 ("cifs: use new enum for ses_status")
1a6a41d4cedd ("cifs: do not use tcpStatus after negotiate completes") cd70a3e8988a ("cifs: use correct lock type in cifs_reconnect()") fb39d30e2272 ("cifs: force new session setup and tcon for dfs") 9a005bea4f59 ("Merge tag '5.18-smb3-fixes-part2' of git://git.samba.org/sfrench/cifs-2.6")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 2f4e429c846972c8405951a9ff7a82aceeca7461 Mon Sep 17 00:00:00 2001
From: Shyam Prasad N <[email protected]>
Date: Mon, 20 Feb 2023 13:02:11 +0000
Subject: [PATCH] cifs: lock chan_lock outside match_session

Coverity had rightly indicated a possible deadlock due to chan_lock being done inside match_session. All callers of match_* functions should pick up the necessary locks and call them.

index 49b37594e991..f42cc7077312 100644
@@ -1721,7 +1721,7 @@ cifs_get_tcp_session(struct smb3_fs_context *ctx,
 	return ERR_PTR(rc);
 }
 
-/* this function must be called with ses_lock held */
+/* this function must be called with ses_lock and chan_lock held */
 static int match_session(struct cifs_ses *ses, struct smb3_fs_context *ctx)
 {
 	if (ctx->sectype != Unspecified &&

@@ -1732,12 +1732,8 @@ 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
 	 */
-	spin_lock(&ses->chan_lock);
-	if (ses->chan_max < ctx->max_channels) {
-		spin_unlock(&ses->chan_lock);
+	if (ses->chan_max < ctx->max_channels)
 		return 0;
-	}
-	spin_unlock(&ses->chan_lock);
 
 	switch (ses->sectype) {
 	case Kerberos:

@@ -1865,10 +1861,13 @@ cifs_find_smb_ses(struct TCP_Server_Info *server, struct smb3_fs_context *ctx)
 			spin_unlock(&ses->ses_lock);
 			continue;
 		}
+		spin_lock(&ses->chan_lock);
 		if (!match_session(ses, ctx)) {
+			spin_unlock(&ses->chan_lock);
 			spin_unlock(&ses->ses_lock);
 			continue;
 		}
+		spin_unlock(&ses->chan_lock);
 		spin_unlock(&ses->ses_lock);
 
 		++ses->ses_count;

@@ -2693,6 +2692,7 @@ cifs_match_super(struct super_block *sb, void *data)
 
 	spin_lock(&tcp_srv->srv_lock);
 	spin_lock(&ses->ses_lock);
+	spin_lock(&ses->chan_lock);
 	spin_lock(&tcon->tc_lock);
 	if (!match_server(tcp_srv, ctx, dfs_super_cmp) ||
 	    !match_session(ses, ctx) ||

@@ -2705,6 +2705,7 @@ cifs_match_super(struct super_block *sb, void *data)
 	rc = compare_mount_options(sb, mnt_data);
 out:
 	spin_unlock(&tcon->tc_lock);
+	spin_unlock(&ses->chan_lock);
 	spin_unlock(&ses->ses_lock);
 	spin_unlock(&tcp_srv->srv_lock);