From: Sachin Prabhu <sprabhu@redhat.com>
Date: Fri, 29 Jul 2016 21:38:20 +0000 (+0100)
Subject: Compare prepaths when comparing superblocks
X-Git-Tag: v3.16.49~9
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f204fa8b8d4809edc87cf137ba684fbfd03b7c1c;p=thirdparty%2Fkernel%2Fstable.git

Compare prepaths when comparing superblocks

commit c1d8b24d18192764fe82067ec6aa8d4c3bf094e0 upstream.

The patch
fs/cifs: make share unaccessible at root level mountable
makes use of prepaths when any component of the underlying path is
inaccessible.

When mounting 2 separate shares having different prepaths but are other
wise similar in other respects, we end up sharing superblocks when we
shouldn't be doing so.

Signed-off-by: Sachin Prabhu <sprabhu@redhat.com>
Tested-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Steve French <smfrench@gmail.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 6d36a1e7a2646..5f2a16751aa7b 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -2751,6 +2751,24 @@ compare_mount_options(struct super_block *sb, struct cifs_mnt_data *mnt_data)
 	return 1;
 }
 
+static int
+match_prepath(struct super_block *sb, struct cifs_mnt_data *mnt_data)
+{
+	struct cifs_sb_info *old = CIFS_SB(sb);
+	struct cifs_sb_info *new = mnt_data->cifs_sb;
+
+	if (old->mnt_cifs_flags & CIFS_MOUNT_USE_PREFIX_PATH) {
+		if (!(new->mnt_cifs_flags & CIFS_MOUNT_USE_PREFIX_PATH))
+			return 0;
+		/* The prepath should be null terminated strings */
+		if (strcmp(new->prepath, old->prepath))
+			return 0;
+
+		return 1;
+	}
+	return 0;
+}
+
 int
 cifs_match_super(struct super_block *sb, void *data)
 {
@@ -2778,7 +2796,8 @@ cifs_match_super(struct super_block *sb, void *data)
 
 	if (!match_server(tcp_srv, volume_info) ||
 	    !match_session(ses, volume_info) ||
-	    !match_tcon(tcon, volume_info->UNC)) {
+	    !match_tcon(tcon, volume_info->UNC) ||
+	    !match_prepath(sb, mnt_data)) {
 		rc = 0;
 		goto out;
 	}