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Message-Id: <20220904112928.1308799-1-asmadeus@codewreck.org>
Date: Sun, 4 Sep 2022 20:29:28 +0900
From: Dominique Martinet <asmadeus@...ewreck.org>
To: v9fs-developer@...ts.sourceforge.net,
Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc: syzkaller-bugs@...glegroups.com, linux_oss@...debyte.com,
linux-kernel@...r.kernel.org,
Dominique Martinet <asmadeus@...ewreck.org>,
syzbot <syzbot+2f20b523930c32c160cc@...kaller.appspotmail.com>
Subject: [PATCH] net/9p: use a dedicated spinlock for trans_fd
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 instead of using spin_lock_irq* variants everywhere
(client.c's protect the idr for 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://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@...kaller.appspotmail.com>
Reported-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Signed-off-by: Dominique Martinet <asmadeus@...ewreck.org>
---
Tetsuo Handa-san, thank you very much!
I'm sorry for not respecting your opinion but it's been a pleasure to
have submissions from someone on JST :)
Both this and your previous patch only impact trans_fd which I can't
test super easily, so while I've sent the patch here I'll only queue it
to -next hopefully next week after I've had time to setup a compatible
server again...
net/9p/trans_fd.c | 42 ++++++++++++++++++++++++++----------------
1 file changed, 26 insertions(+), 16 deletions(-)
diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c
index ef5760971f1e..5b4807411281 100644
--- a/net/9p/trans_fd.c
+++ b/net/9p/trans_fd.c
@@ -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
@@ -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;
@@ -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;
}
@@ -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);
@@ -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);
@@ -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;
@@ -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;
}
@@ -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",
@@ -670,10 +672,10 @@ 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;
@@ -688,11 +690,13 @@ 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);
@@ -700,21 +704,24 @@ static int p9_fd_cancel(struct p9_client *client, struct p9_req_t *req)
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;
}
@@ -723,7 +730,8 @@ 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;
@@ -832,6 +840,7 @@ static int p9_fd_open(struct p9_client *client, int rfd, int wfd)
client->trans = ts;
client->status = Connected;
+ spin_lock_init(&ts->conn.req_lock);
return 0;
@@ -866,6 +875,7 @@ static int p9_socket_open(struct p9_client *client, struct socket *csocket)
p->wr = p->rd = file;
client->trans = p;
client->status = Connected;
+ spin_lock_init(&p->conn.req_lock);
p->rd->f_flags |= O_NONBLOCK;
--
2.35.1
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