p9_read_work and p9_fd_cancelled may be called concurrently.
In some cases, req->req_list may be deleted by both p9_read_work
and p9_fd_cancelled.
We can fix it by ignoring replies associated with a cancelled
request and ignoring cancelled request if message has been received
before lock.
Fixes: 60ff779c4abb ("9p: client: remove unused code and any reference to
"cancelled" function")
Reported-by: syzbot+77a25acfa0382e06a...@syzkaller.appspotmail.com
Signed-off-by: Wang Hai
---
v1->v2:
1. Add ignoring replies associated with a cancelled request.
2. Improved some descriptions suggested by Dominique.
net/9p/trans_fd.c | 15 ++-
1 file changed, 14 insertions(+), 1 deletion(-)
diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c
index 13cd683a658a..3f67803123be 100644
--- a/net/9p/trans_fd.c
+++ b/net/9p/trans_fd.c
@@ -362,6 +362,10 @@ static void p9_read_work(struct work_struct *work)
if (m->rreq->status == REQ_STATUS_SENT) {
list_del(>rreq->req_list);
p9_client_cb(m->client, m->rreq, REQ_STATUS_RCVD);
+ } else if (m->rreq->status == REQ_STATUS_FLSHD) {
+ /* Ignore replies associated with a cancelled request.
*/
+ p9_debug(P9_DEBUG_TRANS,
+"Ignore replies associated with a cancelled
request\n");
} else {
spin_unlock(>client->lock);
p9_debug(P9_DEBUG_ERROR,
@@ -703,11 +707,20 @@ static int p9_fd_cancelled(struct p9_client *client,
struct p9_req_t *req)
{
p9_debug(P9_DEBUG_TRANS, "client %p req %p\n", client, req);
+ spin_lock(>lock);
+ /* Ignore cancelled request if message has been received
+* before lock.
+*/
+ if (req->status == REQ_STATUS_RCVD) {
+ spin_unlock(>lock);
+ return 0;
+ }
+
/* we haven't received a response for oldreq,
* remove it from the list.
*/
- spin_lock(>lock);
list_del(>req_list);
+ req->status = REQ_STATUS_FLSHD;
spin_unlock(>lock);
p9_req_put(req);
--
2.17.1
