On Fri, Jan 12, 2018 at 02:04:24PM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
>
> In the attribute leaf verifier, we can check for obviously bad values of
> firstused and count so that later attempts at lasthash don't run off the
> end of the memory buffer. Found by ones fuzzing hdr.count in xfs/400 with
> KASAN.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> ---
> fs/xfs/libxfs/xfs_attr_leaf.c | 19 ++++++++++++++-----
> 1 file changed, 14 insertions(+), 5 deletions(-)
>
>
> diff --git a/fs/xfs/libxfs/xfs_attr_leaf.c b/fs/xfs/libxfs/xfs_attr_leaf.c
> index 6fddce7..712d458 100644
> --- a/fs/xfs/libxfs/xfs_attr_leaf.c
> +++ b/fs/xfs/libxfs/xfs_attr_leaf.c
> @@ -249,12 +249,13 @@ xfs_attr3_leaf_hdr_to_disk(
>
> static xfs_failaddr_t
> xfs_attr3_leaf_verify(
> - struct xfs_buf *bp)
> + struct xfs_buf *bp)
> {
> - struct xfs_mount *mp = bp->b_target->bt_mount;
> - struct xfs_attr_leafblock *leaf = bp->b_addr;
> - struct xfs_perag *pag = bp->b_pag;
> - struct xfs_attr3_icleaf_hdr ichdr;
> + struct xfs_attr3_icleaf_hdr ichdr;
> + struct xfs_mount *mp = bp->b_target->bt_mount;
> + struct xfs_attr_leafblock *leaf = bp->b_addr;
> + struct xfs_perag *pag = bp->b_pag;
> + struct xfs_attr_leaf_entry *entries;
>
> xfs_attr3_leaf_hdr_from_disk(mp->m_attr_geo, &ichdr, leaf);
>
> @@ -282,6 +283,14 @@ xfs_attr3_leaf_verify(
> if (pag && pag->pagf_init && ichdr.count == 0)
> return __this_address;
>
> + if (ichdr.firstused > mp->m_attr_geo->blksize)
> + return __this_address;
> +
> + entries = xfs_attr3_leaf_entryp(bp->b_addr);
> + if ((char *)&entries[ichdr.count] >=
> + (char *)bp->b_addr + ichdr.firstused)
> + return __this_address;
> +
Hmm, this check confuses me a bit. Should we not consider the header
size in this calculation? (A comment would be useful either way..)
Brian
> /* XXX: need to range check rest of attr header values */
> /* XXX: hash order check? */
>
>
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