linux-kernel - [PATCH 3.16 113/305] smb3: do not attempt cifs operation in smb3 query info error path

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Message-ID: <lsq.1549201508.174683592@decadent.org.uk>
Date:   Sun, 03 Feb 2019 14:45:08 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Ronnie Sahlberg" <lsahlber@...hat.com>,
        "Steve French" <stfrench@...rosoft.com>
Subject: [PATCH 3.16 113/305] smb3: do not attempt cifs operation in smb3
 query info error path

3.16.63-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Steve French <stfrench@...rosoft.com>

commit 1e77a8c204c9d1b655c61751b8ad0fde22421dbb upstream.

If backupuid mount option is sent, we can incorrectly retry
(on access denied on query info) with a cifs (FindFirst) operation
on an smb3 mount which causes the server to force the session close.

We set backup intent on open so no need for this fallback.

See kernel bugzilla 201435

Signed-off-by: Steve French <stfrench@...rosoft.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@...hat.com>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 fs/cifs/inode.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -735,7 +735,15 @@ cifs_get_inode_info(struct inode **inode
 	} else if (rc == -EREMOTE) {
 		cifs_create_dfs_fattr(&fattr, sb);
 		rc = 0;
-	} else if (rc == -EACCES && backup_cred(cifs_sb)) {
+	} else if ((rc == -EACCES) && backup_cred(cifs_sb) &&
+		   (strcmp(server->vals->version_string, SMB1_VERSION_STRING)
+		      == 0)) {
+			/*
+			 * For SMB2 and later the backup intent flag is already
+			 * sent if needed on open and there is no path based
+			 * FindFirst operation to use to retry with
+			 */
+
 			srchinf = kzalloc(sizeof(struct cifs_search_info),
 						GFP_KERNEL);
 			if (srchinf == NULL) {