From 615fcf55d24eeb3747b3300b25f61eed8f9053ab Mon Sep 17 00:00:00 2001 From: Anatoly Burakov Date: Tue, 20 Nov 2018 16:18:46 +0000 Subject: [PATCH] ipc: fix access after async request failure Previous fix for rte_panic has moved setting of alarm before sending the message. This means that whether we send a message, the alarm would still trigger. The comment noted that cleanup would happen in the alarm handler, but that's not what actually happened - instead, in the event of failed send we freed the memory in-place, before putting the request on the queue. This works OK when the message is sent, but when sending the message fails, the alarm would still trigger with a pointer argument that points to non-existent memory, and cause memory corruption. There probably is a "proper" fix for this issue, with correct handling of sent vs. unsent requests, however it would be simpler just to sacrifice the sent request in the (extremely unlikely) event of alarm set failing. The other process would still send a response, but it will be ignored by the sender. Fixes: 45e5f49e87fb ("ipc: remove panic in async request") Signed-off-by: Anatoly Burakov --- lib/librte_eal/common/eal_common_proc.c | 34 ++++++++----------------- 1 file changed, 10 insertions(+), 24 deletions(-) diff --git a/lib/librte_eal/common/eal_common_proc.c b/lib/librte_eal/common/eal_common_proc.c index f65ef56c01..1c3f09aadd 100644 --- a/lib/librte_eal/common/eal_common_proc.c +++ b/lib/librte_eal/common/eal_common_proc.c @@ -827,28 +827,6 @@ mp_request_async(const char *dst, struct rte_mp_msg *req, goto fail; } - /* - * set the alarm before sending message. there are two possible error - * scenarios to consider here: - * - * - if the alarm set fails, we free the memory right there - * - if the alarm set succeeds but sending message fails, then the alarm - * will trigger and clean up the memory - * - * Even if the alarm triggers too early (i.e. immediately), we're still - * holding the lock to pending requests queue, so the interrupt thread - * will just spin until we release the lock, and either release the - * memory, or doesn't find any pending requests in the queue because we - * never added any due to send message failure. - */ - if (rte_eal_alarm_set(ts->tv_sec * 1000000 + ts->tv_nsec / 1000, - async_reply_handle, pending_req) < 0) { - RTE_LOG(ERR, EAL, "Fail to set alarm for request %s:%s\n", - dst, req->name); - ret = -1; - goto fail; - } - ret = send_msg(dst, req, MP_REQ); if (ret < 0) { RTE_LOG(ERR, EAL, "Fail to send request %s:%s\n", @@ -859,10 +837,18 @@ mp_request_async(const char *dst, struct rte_mp_msg *req, ret = 0; goto fail; } - TAILQ_INSERT_TAIL(&pending_requests.requests, pending_req, next); - param->user_reply.nb_sent++; + /* if alarm set fails, we simply ignore the reply */ + if (rte_eal_alarm_set(ts->tv_sec * 1000000 + ts->tv_nsec / 1000, + async_reply_handle, pending_req) < 0) { + RTE_LOG(ERR, EAL, "Fail to set alarm for request %s:%s\n", + dst, req->name); + ret = -1; + goto fail; + } + TAILQ_INSERT_TAIL(&pending_requests.requests, pending_req, next); + return 0; fail: free(pending_req); -- 2.20.1