On Tue, Aug 16, 2016 at 06:50:00PM +0200, David Sterba wrote: > 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....@oracle.com> > > --- > > 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))
Oh, right, I made a mistake when getting the assumption from insert_ptr(), it should be nr > BTRFS_NODEPTRS_PER_BLOCK(root). Thanks, -liubo -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html