isofs: Do not return EACCES for unknown filesystems

When isofs_mount() is called to mount a device read-write, it returns
EACCES even before it checks that the device actually contains an isofs
filesystem. This may confuse mount(8) which then tries to mount all
subsequent filesystem types in read-only mode.

Fix the problem by returning EACCES only once we verify that the device
indeed contains an iso9660 filesystem.

CC: stable@vger.kernel.org
Fixes: 17b7f7cf58926844e1dd40f5eb5348d481deca6a
Reported-by: Kent Overstreet <kent.overstreet@gmail.com>
Reported-by: Karel Zak <kzak@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>

1 files changed, 5 insertions, 3 deletions

diff --git a/fs/isofs/inode.c b/fs/isofs/inode.c
index ad0c745ebad7..871c8b392099 100644
--- a/fs/isofs/inode.c
+++ b/fs/isofs/inode.c
@@ -687,6 +687,11 @@ static int isofs_fill_super(struct super_block *s, void *data, int silent)
         pri_bh = NULL;
 
 root_found:
+        /* We don't support read-write mounts */
+        if (!(s->s_flags & MS_RDONLY)) {
+                error = -EACCES;
+                goto out_freebh;
+        }
 
         if (joliet_level && (pri == NULL || !opt.rock)) {
                 /* This is the case of Joliet with the norock mount flag.
@@ -1501,9 +1506,6 @@ struct inode *__isofs_iget(struct super_block *sb,
 static struct dentry *isofs_mount(struct file_system_type *fs_type,
         int flags, const char *dev_name, void *data)
 {
-        /* We don't support read-write mounts */
-        if (!(flags & MS_RDONLY))
-                return ERR_PTR(-EACCES);
         return mount_bdev(fs_type, flags, dev_name, data, isofs_fill_super);
 }