linux-kernel - Re: [PATCH] staging: erofs: fix unexpected out-of-bound data access

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Date:   Fri, 12 Apr 2019 17:38:12 +0800
From:   Gao Xiang <gaoxiang25@...wei.com>
To:     Chao Yu <yuchao0@...wei.com>
CC:     Ming Lei <ming.lei@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        <devel@...verdev.osuosl.org>, LKML <linux-kernel@...r.kernel.org>,
        <linux-erofs@...ts.ozlabs.org>, Chao Yu <chao@...nel.org>,
        Miao Xie <miaoxie@...wei.com>, <weidu.du@...wei.com>,
        "Fang Wei" <fangwei1@...wei.com>
Subject: Re: [PATCH] staging: erofs: fix unexpected out-of-bound data access

Hi Chao,

On 2019/4/12 17:28, Chao Yu wrote:
> On 2019/4/11 18:55, Gao Xiang wrote:
>> Unexpected out-of-bound data will be read in erofs_read_raw_page
>> after commit 07173c3ec276 ("block: enable multipage bvecs") since
>> one iovec could have multiple pages.
>>
>> Let's fix as what Ming's pointed out in the previous email.
> 
> It will be better to add link address of discussion thread in your commit
> message, since discussion includes more details about how this issue happens.

Thanks for your suggestion.
OK, I will send v2 and add the corresponding link :)

Thanks,
Gao Xiang

> 
>>
>> Suggested-by: Ming Lei <ming.lei@...hat.com>
>> Signed-off-by: Gao Xiang <gaoxiang25@...wei.com>
> 
> Reviewed-by: Chao Yu <yuchao0@...wei.com>
> 
> Thanks,
> 
>> ---
>>
>> It should be fixed from linux-5.1-rc after multi-page bvec feature.
>>
>> Thanks,
>> Gao Xiang
>>
>>  drivers/staging/erofs/data.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/staging/erofs/data.c b/drivers/staging/erofs/data.c
>> index 0714061ba888..c64ec76643d4 100644
>> --- a/drivers/staging/erofs/data.c
>> +++ b/drivers/staging/erofs/data.c
>> @@ -304,7 +304,7 @@ static inline struct bio *erofs_read_raw_page(struct bio *bio,
>>  	*last_block = current_block;
>>  
>>  	/* shift in advance in case of it followed by too many gaps */
>> -	if (unlikely(bio->bi_vcnt >= bio->bi_max_vecs)) {
>> +	if (bio->bi_iter.bi_size >= bio->bi_max_vecs * PAGE_SIZE) {
>>  		/* err should reassign to 0 after submitting */
>>  		err = 0;
>>  		goto submit_bio_out;
>>