init: fix read-write root mount

If mount flags don't have MS_RDONLY, iso9660 returns EACCES without actually
checking if it's an iso image.

This tricks mount_block_root() into retrying with MS_RDONLY.  This results
in a read-only root despite the "rw" boot parameter if the actual
filesystem was checked after iso9660.

I believe the behavior of iso9660 is okay, while that of mount_block_root()
is not.  It should rather try all types without MS_RDONLY and only then
retry with MS_RDONLY.

This change also makes the code more robust against the case when EACCES is
returned despite MS_RDONLY, which would've resulted in a lockup.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 4 insertions, 2 deletions

diff --git a/init/do_mounts.c b/init/do_mounts.c
index 9b3565c41502..eb410083e8e0 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -395,8 +395,6 @@ retry:
                         case 0:
                                 goto out;
                         case -EACCES:
-                                flags |= MS_RDONLY;
-                                goto retry;
                         case -EINVAL:
                                 continue;
                 }
@@ -419,6 +417,10 @@ retry:
 #endif
                 panic("VFS: Unable to mount root fs on %s", b);
         }
+        if (!(flags & MS_RDONLY)) {
+                flags |= MS_RDONLY;
+                goto retry;
+        }
 
         printk("List of all partitions:\n");
         printk_all_partitions();