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Re: [PATCH] xfs_check: fix test for too-high level in v2 dir node

To: Mark Tinguely <tinguely@xxxxxxx>
Subject: Re: [PATCH] xfs_check: fix test for too-high level in v2 dir node
From: Eric Sandeen <sandeen@xxxxxxxxxxx>
Date: Wed, 18 Sep 2013 15:20:00 -0500
Cc: Eric Sandeen <sandeen@xxxxxxxxxx>, "'linux-xfs@xxxxxxxxxxx'" <linux-xfs@xxxxxxxxxxx>
Delivered-to: linux-xfs@xxxxxxxxxxx
In-reply-to: <523A0086.1080000@xxxxxxx>
References: <52322B67.80305@xxxxxxxxxx> <523A0086.1080000@xxxxxxx>
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:17.0) Gecko/20130801 Thunderbird/17.0.8
On 9/18/13 2:35 PM, Mark Tinguely wrote:
> On 09/12/13 16:00, Eric Sandeen wrote:
>> The test as it stands allows level == XFS_DA_NODE_MAXDEPTH (5),
>> but a max depth of 5 equates to level values of 0 through 4.
>>
>> Level 5 would be a depth of 6.
>>
>> Signed-off-by: Eric Sandeen<sandeen@xxxxxxxxxx>
>> ---
>>
> 
>> diff --git a/db/check.c b/db/check.c
>> index cbe55ba..d9e3e3f 100644
>> --- a/db/check.c
>> +++ b/db/check.c
>> @@ -3138,7 +3138,7 @@ process_leaf_node_dir_v2_int(
>>       case XFS_DA_NODE_MAGIC:
>>           node = iocur_top->data;
>>           xfs_da3_node_hdr_from_disk(&nodehdr, node);
>> -        if (nodehdr.level<  1 || nodehdr.level>  XFS_DA_NODE_MAXDEPTH) {
>> +        if (nodehdr.level<  1 || nodehdr.level>= XFS_DA_NODE_MAXDEPTH) {
>>               if (!sflag || v)
>>                   dbprintf(_("bad node block level %d for dir ino "
>>                        "%lld block %d\n"),
> 
> 
> I think the current code is correct.
> 
> 0 is a leaf. levels 1-XFS_DA_NODE_MAXDEPTH are nodes.
> Subtract 1 when used as an index.

        case XFS_DA_NODE_MAGIC:
                node = iocur_top->data;
                xfs_da3_node_hdr_from_disk(&nodehdr, node);
                        to->level = be16_to_cpu(from->hdr.__level);
                if (nodehdr.level < 1 || nodehdr.level > XFS_DA_NODE_MAXDEPTH) {

so nodehdr.level comes directly off the disk.

Hm, ok, let's look at the verifier, xfs_da3_node_verify:

xfs_da3_node_hdr_from_disk /* sets to->level = be16_to_cpu(from->hdr.__level) */

...

        if (ichdr.level == 0)
                return false;
        if (ichdr.level > XFS_DA_NODE_MAXDEPTH)
                return false;

ok, so 1 through XFS_DA_NODE_MAXDEPTH is valid for a generic node.  *shrug* ok
fine, I agree.  It's only xfs_check anyway.  ;)

Feel free to drop this patch then.

But now I'm trying to reconcile it w/ the code in repair,

                        i = da_cursor->active = nodehdr.level;
                        if (i < 1 || i >= XFS_DA_NODE_MAXDEPTH) {

which considers nodehdr.level == XFS_DA_NODE_MAXDEPTH to be problematic, because
i (== nodehdr.level) is used directly as an index into a 
level[XFS_DA_NODE_MAXDEPTH]-sized
array.

So confused.  :/  (Maybe the cursor array needs to be 1 bigger?)

-Eric

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