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authorSeunghun Lee <waydi1@gmail.com>2015-01-03 02:26:49 +0900
committerMiklos Szeredi <mszeredi@suse.cz>2015-01-08 14:47:21 +0100
commit3cdf6fe91041b3afd6761f76254f7b6cbe8020fc (patch)
tree5ec7e50d2280727e59da23dd6af59c12d3c009d2
parenta425c037f3dd8a56469158ab5f37beb46402d958 (diff)
downloadlinux-3cdf6fe91041b3afd6761f76254f7b6cbe8020fc.tar.gz
ovl: Prevent rw remount when it should be ro mount
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@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
-rw-r--r--fs/overlayfs/super.c12
1 files changed, 12 insertions, 0 deletions
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 9e94f4a..b90952f 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -525,10 +525,22 @@ 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 (!(*flags & MS_RDONLY) &&
+ (!ufs->upper_mnt || (ufs->upper_mnt->mnt_sb->s_flags & MS_RDONLY)))
+ return -EROFS;
+
+ 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 {