[PATCH] ovl: Prevent rw remount when it should be ro mount

From: Seunghun Lee
Date: Thu Jan 01 2015 - 10:38:59 EST


Overlayfs should be mounted read-only when upper fs is r/o or nonexistend.
But now it can be remounted read-write and this can causes kernel panic.
So we should prevent read-write remount when the above situation.

Signed-off-by: Seunghun Lee <waydi1@xxxxxxxxx>
---
fs/overlayfs/super.c | 11 +++++++++++
1 file changed, 11 insertions(+)

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 84f3144..8944651 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -522,10 +522,21 @@ static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
return 0;
}

+static int ovl_remount(struct super_block *sb, int *flags, char *data)
+{
+ struct ovl_fs *ufs = sb->s_fs_info;
+
+ if (!ufs->upper_mnt || (ufs->upper_mnt->mnt_sb->s_flags & MS_RDONLY))
+ *flags |= MS_RDONLY;
+
+ return 0;
+}
+
static const struct super_operations ovl_super_operations = {
.put_super = ovl_put_super,
.statfs = ovl_statfs,
.show_options = ovl_show_options,
+ .remount_fs = ovl_remount,
};

enum {
--
2.1.3

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/