Re: [PATCH V2] xfs_repair: test for bad level in dir2 node

Mark Tinguely
2013-09-10T16:43:22Z

On 09/10/13 10:51, Eric Sandeen wrote:
> In traverse_int_dir2block(), the variable 'i' is the level in
> the tree, with 0 being a leaf node. In the "do" loop we
> start at the root, and work our way down to a leaf.
>
> If the first node we read is an interior node with NODE_MAGIC,
> but it tells us that its level is 0 (a leaf), this is clearly
> an inconsistency.
>
> Worse, we'd return with success, bno set, and only level[0]
> in the cursor initialized. Then down this path we'll
> segfault when accessing an uninitialized (and zeroed) member
> of the cursor's level array:
>
> process_node_dir2
> traverse_int_dir2block // returns 0 w/ bno set, only level[0] init'd
> process_leaf_level_dir2
> verify_dir2_path(mp, da_cursor, 0) // p_level == 0
> this_level = p_level + 1;
> node = cursor->level[this_level].bp->b_addr; // level[1] uninit& 0'd
>
> Fix this by recognizing that an interior node w/ level 0 is invalid, and
> error out as for other inconsistencies.
>
> By the time the level 0 test is done, we have already ensured that
> this block has XFS_DA[3]_NODE_MAGIC.
>
> Reported-by: Jan Yves Brueckner<jyb@gmx.com>
> Signed-off-by: Eric Sandeen<sandeen@redhat.com>
> ---
>
> V2: Drop re-test of hdr magic which is guaranteed to be NODE at this point.
> fix "interior inode" - s/b "interior node"
>
> My only testcase for this is Jan Yves Brueckner's badly corrupted
> filesystem image. With this change, we get i.e. :
>
> +bad level in interior inode for directory inode 39869938
> +corrupt block 6 in directory inode 39869957
> + will junk block
>
> diff --git a/repair/dir2.c b/repair/dir2.c
> index 05bd4b7..24db351 100644
> --- a/repair/dir2.c
> +++ b/repair/dir2.c
> @@ -220,6 +220,15 @@ _("bad record count in inode %" PRIu64 ", count = %d, max = %d\n"),
> */
> if (i == -1) {
> i = da_cursor->active = nodehdr.level;
> + /* Tests above ensure that we have NODE_MAGIC here */
> + if (i == 0) {
> + do_warn(
> +_("bad level 0 in interior node for directory inode %" PRIu64 "\n"),
> + da_cursor->ino);
> + libxfs_putbuf(bp);
> + i = -1;
> + goto error_out;
> + }
> if (i>= XFS_DA_NODE_MAXDEPTH) {
> do_warn(
> _("bad header depth for directory inode %" PRIu64 "\n"),
>

But moving the check out of the (i == -1) block, then the loop can check
all the intermediate nodes along the way and also the ending leaf.

--Mark.