btrfs: validate qgroup inherit for SNAP_CREATE_V2 ioctl

The problem is we're copying "inherit" from user space but we don't
necessarily know that we're copying enough data for a 64 byte
struct.  Then the next problem is that 'inherit' has a variable size
array at the end, and we have to verify that array is the size we
expected.

Fixes: 6f72c7e20dba ("Btrfs: add qgroup inheritance")
CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index a8c60d4..1b837c0 100644 (file)
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1935,7 +1935,10 @@ static noinline int btrfs_ioctl_snap_create_v2(struct file *file,
        if (vol_args->flags & BTRFS_SUBVOL_RDONLY)
                readonly = true;
        if (vol_args->flags & BTRFS_SUBVOL_QGROUP_INHERIT) {
-               if (vol_args->size > PAGE_SIZE) {
+               u64 nums;
+
+               if (vol_args->size < sizeof(*inherit) ||
+                   vol_args->size > PAGE_SIZE) {
                        ret = -EINVAL;
                        goto free_args;
                }
@@ -1944,6 +1947,20 @@ static noinline int btrfs_ioctl_snap_create_v2(struct file *file,
                        ret = PTR_ERR(inherit);
                        goto free_args;
                }
+
+               if (inherit->num_qgroups > PAGE_SIZE ||
+                   inherit->num_ref_copies > PAGE_SIZE ||
+                   inherit->num_excl_copies > PAGE_SIZE) {
+                       ret = -EINVAL;
+                       goto free_inherit;
+               }
+
+               nums = inherit->num_qgroups + 2 * inherit->num_ref_copies +
+                      2 * inherit->num_excl_copies;
+               if (vol_args->size != struct_size(inherit, qgroups, nums)) {
+                       ret = -EINVAL;
+                       goto free_inherit;
+               }
        }
 
        ret = __btrfs_ioctl_snap_create(file, vol_args->name, vol_args->fd,