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9p/trans_fd: Fix concurrency del of req_list in p9_fd_cancelled/p9_read_work

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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.

Link: http://lkml.kernel.org/r/20200612090833.36149-1-wanghai38@huawei.com
Fixes: 60ff779c4a ("9p: client: remove unused code and any reference to "cancelled" function")
Cc: <stable@vger.kernel.org> # v3.12+
Reported-by: syzbot+77a25acfa0382e06ab23@syzkaller.appspotmail.com
Signed-off-by: Wang Hai <wanghai38@huawei.com>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
This commit is contained in:
Wang Hai 2020-06-12 17:08:33 +08:00 committed by Dominique Martinet
parent a39c46067c
commit 74d6a5d566
1 changed files with 14 additions and 1 deletions
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15
net/9p/trans_fd.c
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@ -362,6 +362,10 @@ static void p9_read_work(struct work_struct *work)
if (m->rreq->status == REQ_STATUS_SENT) {
list_del(&m->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(&m->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(&client->lock);
/* Ignore cancelled request if message has been received
* before lock.
*/
if (req->status == REQ_STATUS_RCVD) {
spin_unlock(&client->lock);
return 0;
}
/* we haven't received a response for oldreq,
* remove it from the list.
*/
spin_lock(&client->lock);
list_del(&req->req_list);
req->status = REQ_STATUS_FLSHD;
spin_unlock(&client->lock);
p9_req_put(req);