Re: [dpdk-dev] [PATCH 1/2] eal/ipc: fix use-after-free in synchronous requests

["Tan, Jianfeng" <jianfeng.tan@intel.com>]

On 4/13/2018 7:54 PM, Anatoly Burakov wrote:
> Previously, we were adding synchronous requests to request list, we
> were doing it after checking if request existed. However, we only
> removed the request from the request list if we have succeeded in
> sending the request. In case of failed request send, we left an
> invalid pointer in the request list.
>
> Fix this by only adding request to the list once we succeed in
> sending it.
>
> Fixes: 783b6e54971d ("eal: add synchronous multi-process communication")
> Cc: jianfeng.tan@intel.com
>
> Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>

Nice catch.

Acked-by: Jianfeng Tan <jianfeng.tan@intel.com>


> ---
>   lib/librte_eal/common/eal_common_proc.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/lib/librte_eal/common/eal_common_proc.c b/lib/librte_eal/common/eal_common_proc.c
> index c888c84..e3eb430 100644
> --- a/lib/librte_eal/common/eal_common_proc.c
> +++ b/lib/librte_eal/common/eal_common_proc.c
> @@ -922,8 +922,6 @@ mp_request_sync(const char *dst, struct rte_mp_msg *req,
>   
>   	pthread_mutex_lock(&pending_requests.lock);
>   	exist = find_sync_request(dst, req->name);
> -	if (!exist)
> -		TAILQ_INSERT_TAIL(&pending_requests.requests, &sync_req, next);
>   	if (exist) {
>   		RTE_LOG(ERR, EAL, "A pending request %s:%s\n", dst, req->name);
>   		rte_errno = EEXIST;
> @@ -939,6 +937,8 @@ mp_request_sync(const char *dst, struct rte_mp_msg *req,
>   	} else if (ret == 0)
>   		return 0;
>   
> +	TAILQ_INSERT_TAIL(&pending_requests.requests, &sync_req, next);
> +
>   	reply->nb_sent++;
>   
>   	do {