cifs: close sget() races

have ->s_fs_info set by the set() callback passed to sget()

Acked-by: Pavel Shilovsky <piastryyy@gmail.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 9 insertions, 3 deletions

diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 46960b7ee433..ba2b2da360d3 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -629,6 +629,13 @@ out:
         return dparent;
 }
 
+static int cifs_set_super(struct super_block *sb, void *data)
+{
+        struct cifs_mnt_data *mnt_data = data;
+        sb->s_fs_info = mnt_data->cifs_sb;
+        return set_anon_super(sb, NULL);
+}
+
 static struct dentry *
 cifs_do_mount(struct file_system_type *fs_type,
               int flags, const char *dev_name, void *data)
@@ -678,14 +685,14 @@ cifs_do_mount(struct file_system_type *fs_type,
         mnt_data.cifs_sb = cifs_sb;
         mnt_data.flags = flags;
 
-        sb = sget(fs_type, cifs_match_super, set_anon_super, &mnt_data);
+        sb = sget(fs_type, cifs_match_super, cifs_set_super, &mnt_data);
         if (IS_ERR(sb)) {
                 root = ERR_CAST(sb);
                 cifs_umount(cifs_sb);
                 goto out;
         }
 
-        if (sb->s_fs_info) {
+        if (sb->s_root) {
                 cFYI(1, "Use existing superblock");
                 cifs_umount(cifs_sb);
                 goto out_shared;
@@ -694,7 +701,6 @@ cifs_do_mount(struct file_system_type *fs_type,
         sb->s_flags = flags;
         /* BB should we make this contingent on mount parm? */
         sb->s_flags |= MS_NODIRATIME | MS_NOATIME;
-        sb->s_fs_info = cifs_sb;
 
         rc = cifs_read_super(sb);
         if (rc) {