On Wed, Aug 03, 2016 at 12:57:28PM -0700, Liu Bo wrote:
> When btree node (level = 1) has nritems which equals to zero,
> we can end up with panic due to insert_ptr()'s
>
> BUG_ON(slot > nritems);
>
> where slot is 1 and nritems is 0, as copy_for_split() calls
> insert_ptr(.., path->slots[1] + 1, ...);
>
> A invalid value results in the whole mess, this adds the check
> for btree's node nritems so that we stop reading block when
> when something is wrong.
>
> Signed-off-by: Liu Bo <bo.li.liu@xxxxxxxxxx>
> ---
> fs/btrfs/disk-io.c | 17 +++++++++++++++++
> 1 file changed, 17 insertions(+)
>
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index 37d1780..a5a22be 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -612,6 +612,20 @@ static noinline int check_leaf(struct btrfs_root *root,
> return 0;
> }
>
> +static noinline int check_node(struct btrfs_root *root,
> + struct extent_buffer *node)
> +{
> + unsigned long nr = btrfs_header_nritems(node);
> +
> + if (nr <= 0 || nr >= BTRFS_NODEPTRS_PER_BLOCK(root)) {
nr is unsigned, so it's just "== 0"
and the BTRFS_NODEPTRS_PER_BLOCK value is inclusive, which should
explain Holger's findings.
493 * sizeof (btrfs_key_ptr) + sizeof (btrfs_header) + slack = nodesize
493 * 33 + 101 + slack = 16k (the closest value)
gives slack = 14 (smaller than sizeof (btrfs_key_ptr))
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
