On 8/17/20 3:43 AM, gregkh@xxxxxxxxxxxxxxxxxxx wrote:
>
> The patch below does not apply to the 5.7-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@xxxxxxxxxxxxxxx>.
Here's one that works.
--
Jens Axboe
>From f82e53af6cfc19bde5c003ddfeeb5169c35fadf7 Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@xxxxxxxxx>
Date: Sat, 15 Aug 2020 11:44:50 -0700
Subject: [PATCH] io_uring: sanitize double poll handling
There's a bit of confusion on the matching pairs of poll vs double poll,
depending on if the request is a pure poll (IORING_OP_POLL_ADD) or
poll driven retry.
Add io_poll_get_double() that returns the double poll waitqueue, if any,
and io_poll_get_single() that returns the original poll waitqueue. With
that, remove the argument to io_poll_remove_double().
Finally ensure that wait->private is cleared once the double poll handler
has run, so that remove knows it's already been seen.
Cc: stable@xxxxxxxxxxxxxxx # v5.8
Reported-by: syzbot+7f617d4a9369028b8a2c@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 18bceab101ad ("io_uring: allow POLL_ADD with double poll_wait() users")
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
fs/io_uring.c | 32 ++++++++++++++++++++++++--------
1 file changed, 24 insertions(+), 8 deletions(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 7e54da9d0dcb..11bb49fa9593 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -4221,9 +4221,24 @@ static bool io_poll_rewait(struct io_kiocb *req, struct io_poll_iocb *poll)
return false;
}
-static void io_poll_remove_double(struct io_kiocb *req, void *data)
+static struct io_poll_iocb *io_poll_get_double(struct io_kiocb *req)
{
- struct io_poll_iocb *poll = data;
+ /* pure poll stashes this in ->io, poll driven retry elsewhere */
+ if (req->opcode == IORING_OP_POLL_ADD)
+ return (struct io_poll_iocb *) req->io;
+ return req->apoll->double_poll;
+}
+
+static struct io_poll_iocb *io_poll_get_single(struct io_kiocb *req)
+{
+ if (req->opcode == IORING_OP_POLL_ADD)
+ return &req->poll;
+ return &req->apoll->poll;
+}
+
+static void io_poll_remove_double(struct io_kiocb *req)
+{
+ struct io_poll_iocb *poll = io_poll_get_double(req);
lockdep_assert_held(&req->ctx->completion_lock);
@@ -4243,7 +4258,7 @@ static void io_poll_complete(struct io_kiocb *req, __poll_t mask, int error)
{
struct io_ring_ctx *ctx = req->ctx;
- io_poll_remove_double(req, req->io);
+ io_poll_remove_double(req);
req->poll.done = true;
io_cqring_fill_event(req, error ? error : mangle_poll(mask));
io_commit_cqring(ctx);
@@ -4285,7 +4300,7 @@ static int io_poll_double_wake(struct wait_queue_entry *wait, unsigned mode,
int sync, void *key)
{
struct io_kiocb *req = wait->private;
- struct io_poll_iocb *poll = req->apoll->double_poll;
+ struct io_poll_iocb *poll = io_poll_get_single(req);
__poll_t mask = key_to_poll(key);
/* for instances that support it check for an event match first: */
@@ -4299,6 +4314,8 @@ static int io_poll_double_wake(struct wait_queue_entry *wait, unsigned mode,
done = list_empty(&poll->wait.entry);
if (!done)
list_del_init(&poll->wait.entry);
+ /* make sure double remove sees this as being gone */
+ wait->private = NULL;
spin_unlock(&poll->head->lock);
if (!done)
__io_async_wake(req, poll, mask, io_poll_task_func);
@@ -4534,7 +4551,7 @@ static bool io_arm_poll_handler(struct io_kiocb *req)
ret = __io_arm_poll_handler(req, &apoll->poll, &ipt, mask,
io_async_wake);
if (ret || ipt.error) {
- io_poll_remove_double(req, apoll->double_poll);
+ io_poll_remove_double(req);
spin_unlock_irq(&ctx->completion_lock);
memcpy(&req->work, &apoll->work, sizeof(req->work));
kfree(apoll->double_poll);
@@ -4567,14 +4584,13 @@ static bool io_poll_remove_one(struct io_kiocb *req)
{
bool do_complete;
+ io_poll_remove_double(req);
+
if (req->opcode == IORING_OP_POLL_ADD) {
- io_poll_remove_double(req, req->io);
do_complete = __io_poll_remove_one(req, &req->poll);
} else {
struct async_poll *apoll = req->apoll;
- io_poll_remove_double(req, apoll->double_poll);
-
/* non-poll requests have submit ref still */
do_complete = __io_poll_remove_one(req, &apoll->poll);
if (do_complete) {
--
2.28.0
