Re: [PATCH] net/rds: Fix a use after free in rds_message_map_pages

[lyl2019@mail.ustc.edu.cn]

Just as a reminder,
there has been no reply to this message for more than a week.

Could someone help to fix this issue?

> -----原始邮件-----
> 发件人: "Lv Yunlong" <lyl2019@mail.ustc.edu.cn>
> 发送时间: 2021-03-11 16:46:16 (星期四)
> 收件人: santosh.shilimkar@oracle.com, davem@davemloft.net, kuba@kernel.org
> 抄送: netdev@vger.kernel.org, linux-rdma@vger.kernel.org, rds-devel@oss.oracle.com, linux-kernel@vger.kernel.org, "Lv Yunlong" <lyl2019@mail.ustc.edu.cn>
> 主题: [PATCH] net/rds: Fix a use after free in rds_message_map_pages
> 
> In rds_message_map_pages, rds_message_put() will free rm.
> Maybe store the value of rm->data.op_sg ahead of rds_message_put()
> is better. Otherwise other threads could allocate the freed chunk
> and may change the value of rm->data.op_sg.
> 
> Signed-off-by: Lv Yunlong <lyl2019@mail.ustc.edu.cn>
> ---
>  net/rds/message.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/net/rds/message.c b/net/rds/message.c
> index 071a261fdaab..392e3a2f41a0 100644
> --- a/net/rds/message.c
> +++ b/net/rds/message.c
> @@ -347,8 +347,9 @@ struct rds_message *rds_message_map_pages(unsigned long *page_addrs, unsigned in
>  	rm->data.op_nents = DIV_ROUND_UP(total_len, PAGE_SIZE);
>  	rm->data.op_sg = rds_message_alloc_sgs(rm, num_sgs);
>  	if (IS_ERR(rm->data.op_sg)) {
> +		struct scatterlist *tmp = rm->data.op_sg;
>  		rds_message_put(rm);
> -		return ERR_CAST(rm->data.op_sg);
> +		return ERR_CAST(tmp);
>  	}
>  
>  	for (i = 0; i < rm->data.op_nents; ++i) {
> -- 
> 2.25.1
>