linux-ext4 - Re: [PATCH v2] ext4: avoid eh_entries overflow before insert extent

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Date:	Fri, 24 Jun 2011 16:27:29 +0800
From:	Robin Dong <hao.bigrat@...il.com>
To:	Yongqiang Yang <xiaoqiangnk@...il.com>
Cc:	Eric Sandeen <sandeen@...hat.com>, linux-ext4@...r.kernel.org,
	Robin Dong <sanbai@...bao.com>
Subject: Re: [PATCH v2] ext4: avoid eh_entries overflow before insert extent_idx

2011/6/24 Yongqiang Yang <xiaoqiangnk@...il.com>:
> On Thu, Jun 23, 2011 at 10:57 PM, Eric Sandeen <sandeen@...hat.com> wrote:
>> On 6/23/11 3:47 AM, Robin Dong wrote:
>>> If eh_entries is equal to (or greater than) eh_max, the operation of
>>> inserting new extent_idx will make number of entries overflow.
>>> So check eh_entries before inserting the new extent_idx.
>>
>> Do you have any testcase you can share which shows this bug?
> I am not sure if Robin has any test case.
>
> According to code, I think there is no bug case.  Because this
> function is called by ext4_ext_split() and ext4_ext_split() is called
> only if the index block has free space.
>
> I think the right logic should be as this patch shows, that is, we
> should lookup the capacity before insertion.

Exactly!  :-)

-- 
--
Best Regard
Robin Dong


>
> Yongqiang.
>>
>> Thanks,
>> -Eric
>>
>>> Signed-off-by: Robin Dong <sanbai@...bao.com>
>>> ---
>>>  fs/ext4/extents.c |   18 ++++++++++--------
>>>  1 files changed, 10 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
>>> index eb63c7b..792e77e 100644
>>> --- a/fs/ext4/extents.c
>>> +++ b/fs/ext4/extents.c
>>> @@ -776,6 +776,16 @@ static int ext4_ext_insert_index(handle_t *handle, struct inode *inode,
>>>                                logical, le32_to_cpu(curp->p_idx->ei_block));
>>>               return -EIO;
>>>       }
>>> +
>>> +     if (unlikely(le16_to_cpu(curp->p_hdr->eh_entries)
>>> +                          >= le16_to_cpu(curp->p_hdr->eh_max))) {
>>> +             EXT4_ERROR_INODE(inode,
>>> +                              "eh_entries %d >= eh_max %d!",
>>> +                              le16_to_cpu(curp->p_hdr->eh_entries),
>>> +                              le16_to_cpu(curp->p_hdr->eh_max));
>>> +             return -EIO;
>>> +     }
>>> +
>>>       len = EXT_MAX_INDEX(curp->p_hdr) - curp->p_idx;
>>>       if (logical > le32_to_cpu(curp->p_idx->ei_block)) {
>>>               /* insert after */
>>> @@ -805,14 +815,6 @@ static int ext4_ext_insert_index(handle_t *handle, struct inode *inode,
>>>       ext4_idx_store_pblock(ix, ptr);
>>>       le16_add_cpu(&curp->p_hdr->eh_entries, 1);
>>>
>>> -     if (unlikely(le16_to_cpu(curp->p_hdr->eh_entries)
>>> -                          > le16_to_cpu(curp->p_hdr->eh_max))) {
>>> -             EXT4_ERROR_INODE(inode,
>>> -                              "eh_entries %d > eh_max %d!",
>>> -                              le16_to_cpu(curp->p_hdr->eh_entries),
>>> -                              le16_to_cpu(curp->p_hdr->eh_max));
>>> -             return -EIO;
>>> -     }
>>>       if (unlikely(ix > EXT_LAST_INDEX(curp->p_hdr))) {
>>>               EXT4_ERROR_INODE(inode, "ix > EXT_LAST_INDEX!");
>>>               return -EIO;
>>
>> --
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>>
>
>
>
> --
> Best Wishes
> Yongqiang Yang
>
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