Overlayfs should be mounted read-only when upper-fs is read-only or nonexistent.
But now it can be remounted read-write and this can cause kernel panic.
So we should prevent read-write remount when the above situation happens.
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
--
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