According to commit "vfs: parse: deal with zero length string value", kernel will set the param->string to null pointer in vfs_parse_fs_string() if fs string has zero length. Yet the problem is that, ceph_parse_mount_param() will dereferences the param->string, without checking whether it is a null pointer, which may trigger a null-ptr-deref bug. This patch solves it by adding sanity check on param->string in ceph_parse_mount_param(). Signed-off-by: Hawkins Jiawei <yin31149@xxxxxxxxx> --- fs/ceph/super.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/ceph/super.c b/fs/ceph/super.c index 3fc48b43cab0..341e23fe29eb 100644 --- a/fs/ceph/super.c +++ b/fs/ceph/super.c @@ -417,6 +417,9 @@ static int ceph_parse_mount_param(struct fs_context *fc, param->string = NULL; break; case Opt_mds_namespace: + if (!param->string) + return invalfc(fc, "Bad value '%s' for mount option '%s'\n", + param->string, param->key); if (!namespace_equals(fsopt, param->string, strlen(param->string))) return invalfc(fc, "Mismatching mds_namespace"); kfree(fsopt->mds_namespace); -- 2.25.1
