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9p/trans_fd: avoid sending req to a cancelled conn

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When a connection is cancelled by p9_conn_cancel(), all requests on it
should be cancelled---mark req->status as REQ_STATUS_ERROR. However,
because a race over m->err between p9_conn_cancel() and p9_fd_request(),
p9_fd_request might see the old value of m->err, think that the connection
is NOT cancelled, and then add new requests to this cancelled connection.

Fixing this issue by lock-protecting the check on m->err.

Signed-off-by: Sishuai Gong <sishuai.system@gmail.com>
Message-ID: <AA2DB53B-DFC7-4B88-9515-E4C9AFA6435D@gmail.com>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
Reviewed-by: Christian Schoenebeck <linux_oss@crudebyte.com>
This commit is contained in:
Sishuai Gong 2023-08-08 12:44:31 -04:00 committed by Dominique Martinet
parent 05d3ef8bba
commit 58e3ce7673
1 changed files with 6 additions and 2 deletions
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8
net/9p/trans_fd.c
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@ -671,10 +671,14 @@ static int p9_fd_request(struct p9_client *client, struct p9_req_t *req)
p9_debug(P9_DEBUG_TRANS, "mux %p task %p tcall %p id %d\n",
m, current, &req->tc, req->tc.id);
if (m->err < 0)
return m->err;
spin_lock(&m->req_lock);
if (m->err < 0) {
spin_unlock(&m->req_lock);
return m->err;
}
WRITE_ONCE(req->status, REQ_STATUS_UNSENT);
list_add_tail(&req->req_list, &m->unsent_req_list);
spin_unlock(&m->req_lock);