Re: [PATCH v2] net/rds: Fix a use after free in rds_message_map_pages

[Haakon Bugge]

> On 31 Mar 2021, at 03:59, Lv Yunlong <lyl2019@xxxxxxxxxxxxxxxx> wrote:
> 
> In rds_message_map_pages, the rm is freed by rds_message_put(rm).
> But rm is still used by rm->data.op_sg in return value.
> 
> My patch assigns ERR_CAST(rm->data.op_sg) to err before the rm is
> freed to avoid the uaf.
> 
> Fixes: 7dba92037baf3 ("net/rds: Use ERR_PTR for rds_message_alloc_sgs()")
> Signed-off-by: Lv Yunlong <lyl2019@xxxxxxxxxxxxxxxx>

Reviewed-by: Håkon Bugge <haakon.bugge@xxxxxxxxxx>


Thanks for fixing this:-)

Håkon


> ---
> 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..799034e0f513 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)) {
> +		void *err = ERR_CAST(rm->data.op_sg);
> 		rds_message_put(rm);
> -		return ERR_CAST(rm->data.op_sg);
> +		return err;
> 	}
> 
> 	for (i = 0; i < rm->data.op_nents; ++i) {
> -- 
> 2.25.1
> 
>