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io_uring: sanitize double poll handling

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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@vger.kernel.org # v5.8
Reported-by: syzbot+7f617d4a9369028b8a2c@syzkaller.appspotmail.com
Fixes: 18bceab101 ("io_uring: allow POLL_ADD with double poll_wait() users")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2020-08-15 11:44:50 -07:00
parent 227c0c9673
commit d4e7cd36a9
1 changed files with 25 additions and 9 deletions
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34
fs/io_uring.c
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@ -4649,9 +4649,24 @@ 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);
@ -4671,7 +4686,7 @@ 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);
@ -4711,7 +4726,7 @@ 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: */
@ -4725,6 +4740,8 @@ 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);
@ -4808,7 +4825,7 @@ static void io_async_task_func(struct callback_head *cb)
if (hash_hashed(&req->hash_node))
hash_del(&req->hash_node);
io_poll_remove_double(req, apoll->double_poll);
io_poll_remove_double(req);
spin_unlock_irq(&ctx->completion_lock);
if (!READ_ONCE(apoll->poll.canceled))
@ -4919,7 +4936,7 @@ 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);
kfree(apoll->double_poll);
kfree(apoll);
@ -4951,14 +4968,13 @@ 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) {