On Sun, Jan 25, 2009 at 9:45 PM, Eric Sandeen <sandeen@xxxxxxxxxx> wrote:
> Manish Katiyar wrote:
>> On Tue, Jan 20, 2009 at 10:36 PM, Manish Katiyar <mkatiyar@xxxxxxxxx> wrote:
>>> ext2_quota_read doesn't bzeroes tmp_bh before calling ext2_get_block()
>>> where we access the b_size of it. Since it is a local variable it
>>> might contain some garbage. Make sure it is filled with zero before
>>> passing.
>>
>> Hi Ted/mingming,
>>
>> Any feedback on this ??
>
> This looks ok to me, Manish. I'm curious, did you see this fail in real
> life, and if so, what'd the failure look like?
Actually no......I realised this while going through the code. I was
also wondering why we haven't hit this till now. Since ext{3,4} don't
have this issue, the only reason I can think of is because ext2 with
quota is not very much used or somehow we are lucky.
>
> With the change, the tmp_bh bh_size is 0, so maxblocks down the
> get_block path is also 0, but I guess that works out ok.
Yes, but that is better than having a random garbage. Isn't it ?
Thanks -
Manish
>
> -Eric
>
>> Thanks -
>> Manish
>>
>>> Signed-off-by : Manish Katiyar <mkatiyar@xxxxxxxxx>
>>> ---
>>> fs/ext2/super.c | 4 ++--
>>> 1 files changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/fs/ext2/super.c b/fs/ext2/super.c
>>> index da8bdea..d10aa44 100644
>>> --- a/fs/ext2/super.c
>>> +++ b/fs/ext2/super.c
>>> @@ -1327,7 +1327,7 @@ static ssize_t ext2_quota_read(struct
>>> super_block *sb, int type, char *data,
>>> tocopy = sb->s_blocksize - offset < toread ?
>>> sb->s_blocksize - offset : toread;
>>>
>>> - tmp_bh.b_state = 0;
>>> + memset(&tmp_bh, 0, sizeof(struct buffer_head));
>>> err = ext2_get_block(inode, blk, &tmp_bh, 0);
>>> if (err < 0)
>>> return err;
>>> @@ -1366,7 +1366,7 @@ static ssize_t ext2_quota_write(struct
>>> super_block *sb, int type,
>>> tocopy = sb->s_blocksize - offset < towrite ?
>>> sb->s_blocksize - offset : towrite;
>>>
>>> - tmp_bh.b_state = 0;
>>> + memset(&tmp_bh, 0, sizeof(struct buffer_head));
>>> err = ext2_get_block(inode, blk, &tmp_bh, 1);
>>> if (err < 0)
>>> goto out;
>>> --
>>> 1.5.4.3
>>>
>>>
>>> Thanks -
>>> Manish
>>>
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