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net/9p: use a dedicated spinlock for trans_fd
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Shamelessly copying the explanation from Tetsuo Handa's suggested
patch[1] (slightly reworded):
syzbot is reporting inconsistent lock state in p9_req_put()[2],
for p9_tag_remove() from p9_req_put() from IRQ context is using
spin_lock_irqsave() on "struct p9_client"->lock but trans_fd
(not from IRQ context) is using spin_lock().

Since the locks actually protect different things in client.c and in
trans_fd.c, just replace trans_fd.c's lock by a new one specific to the
transport (client.c's protect the idr for fid/tag allocations,
while trans_fd.c's protects its own req list and request status field
that acts as the transport's state machine)

Link: https://lore.kernel.org/r/20220904112928.1308799-1-asmadeus@codewreck.org
Link: https://lkml.kernel.org/r/2470e028-9b05-2013-7198-1fdad071d999@I-love.SAKURA.ne.jp [1]
Link: https://syzkaller.appspot.com/bug?extid=2f20b523930c32c160cc [2]
Reported-by: syzbot <syzbot+2f20b523930c32c160cc@syzkaller.appspotmail.com>
Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
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@martinetd
martinetd committed Oct 7, 2022
1 parent ef57528 commit e5cfd99
Showing 1 changed file with 25 additions and 16 deletions.
41 changes: 25 additions & 16 deletions net/9p/trans_fd.c
View file
Expand Up @@ -91,6 +91,7 @@ struct p9_poll_wait {
* @mux_list: list link for mux to manage multiple connections (?)
* @client: reference to client instance for this connection
* @err: error state
* @req_lock: lock protecting req_list and requests statuses
* @req_list: accounting for requests which have been sent
* @unsent_req_list: accounting for requests that haven't been sent
* @rreq: read request
Expand All @@ -114,6 +115,7 @@ struct p9_conn {
struct list_head mux_list;
struct p9_client *client;
int err;
spinlock_t req_lock;
struct list_head req_list;
struct list_head unsent_req_list;
struct p9_req_t *rreq;
Expand Down Expand Up @@ -189,10 +191,10 @@ static void p9_conn_cancel(struct p9_conn *m, int err)

p9_debug(P9_DEBUG_ERROR, "mux %p err %d\n", m, err);

spin_lock(&m->client->lock);
spin_lock(&m->req_lock);

if (m->err) {
spin_unlock(&m->client->lock);
spin_unlock(&m->req_lock);
return;
}

Expand All @@ -205,7 +207,7 @@ static void p9_conn_cancel(struct p9_conn *m, int err)
list_move(&req->req_list, &cancel_list);
}

spin_unlock(&m->client->lock);
spin_unlock(&m->req_lock);

list_for_each_entry_safe(req, rtmp, &cancel_list, req_list) {
p9_debug(P9_DEBUG_ERROR, "call back req %p\n", req);
Expand Down Expand Up @@ -360,7 +362,7 @@ static void p9_read_work(struct work_struct *work)
if ((m->rreq) && (m->rc.offset == m->rc.capacity)) {
p9_debug(P9_DEBUG_TRANS, "got new packet\n");
m->rreq->rc.size = m->rc.offset;
spin_lock(&m->client->lock);
spin_lock(&m->req_lock);
if (m->rreq->status == REQ_STATUS_SENT) {
list_del(&m->rreq->req_list);
p9_client_cb(m->client, m->rreq, REQ_STATUS_RCVD);
Expand All @@ -369,14 +371,14 @@ static void p9_read_work(struct work_struct *work)
p9_debug(P9_DEBUG_TRANS,
"Ignore replies associated with a cancelled request\n");
} else {
spin_unlock(&m->client->lock);
spin_unlock(&m->req_lock);
p9_debug(P9_DEBUG_ERROR,
"Request tag %d errored out while we were reading the reply\n",
m->rc.tag);
err = -EIO;
goto error;
}
spin_unlock(&m->client->lock);
spin_unlock(&m->req_lock);
m->rc.sdata = NULL;
m->rc.offset = 0;
m->rc.capacity = 0;
Expand Down Expand Up @@ -454,10 +456,10 @@ static void p9_write_work(struct work_struct *work)
}

if (!m->wsize) {
spin_lock(&m->client->lock);
spin_lock(&m->req_lock);
if (list_empty(&m->unsent_req_list)) {
clear_bit(Wworksched, &m->wsched);
spin_unlock(&m->client->lock);
spin_unlock(&m->req_lock);
return;
}

Expand All @@ -472,7 +474,7 @@ static void p9_write_work(struct work_struct *work)
m->wpos = 0;
p9_req_get(req);
m->wreq = req;
spin_unlock(&m->client->lock);
spin_unlock(&m->req_lock);
}

p9_debug(P9_DEBUG_TRANS, "mux %p pos %d size %d\n",
Expand Down Expand Up @@ -589,6 +591,7 @@ static void p9_conn_create(struct p9_client *client)
INIT_LIST_HEAD(&m->mux_list);
m->client = client;

spin_lock_init(&m->req_lock);
INIT_LIST_HEAD(&m->req_list);
INIT_LIST_HEAD(&m->unsent_req_list);
INIT_WORK(&m->rq, p9_read_work);
Expand Down Expand Up @@ -670,10 +673,10 @@ static int p9_fd_request(struct p9_client *client, struct p9_req_t *req)
if (m->err < 0)
return m->err;

spin_lock(&client->lock);
spin_lock(&m->req_lock);
req->status = REQ_STATUS_UNSENT;
list_add_tail(&req->req_list, &m->unsent_req_list);
spin_unlock(&client->lock);
spin_unlock(&m->req_lock);

if (test_and_clear_bit(Wpending, &m->wsched))
n = EPOLLOUT;
Expand All @@ -688,33 +691,38 @@ static int p9_fd_request(struct p9_client *client, struct p9_req_t *req)

static int p9_fd_cancel(struct p9_client *client, struct p9_req_t *req)
{
struct p9_trans_fd *ts = client->trans;
struct p9_conn *m = &ts->conn;
int ret = 1;

p9_debug(P9_DEBUG_TRANS, "client %p req %p\n", client, req);

spin_lock(&client->lock);
spin_lock(&m->req_lock);

if (req->status == REQ_STATUS_UNSENT) {
list_del(&req->req_list);
req->status = REQ_STATUS_FLSHD;
p9_req_put(client, req);
ret = 0;
}
spin_unlock(&client->lock);
spin_unlock(&m->req_lock);

return ret;
}

static int p9_fd_cancelled(struct p9_client *client, struct p9_req_t *req)
{
struct p9_trans_fd *ts = client->trans;
struct p9_conn *m = &ts->conn;

p9_debug(P9_DEBUG_TRANS, "client %p req %p\n", client, req);

spin_lock(&client->lock);
spin_lock(&m->req_lock);
/* Ignore cancelled request if message has been received
* before lock.
*/
if (req->status == REQ_STATUS_RCVD) {
spin_unlock(&client->lock);
spin_unlock(&m->req_lock);
return 0;
}

Expand All @@ -723,7 +731,8 @@ static int p9_fd_cancelled(struct p9_client *client, struct p9_req_t *req)
*/
list_del(&req->req_list);
req->status = REQ_STATUS_FLSHD;
spin_unlock(&client->lock);
spin_unlock(&m->req_lock);

p9_req_put(client, req);

return 0;
Expand Down

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