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io_uring: don't use poll handler if file can't be nonblocking read/written

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There's no point in using the poll handler if we can't do a nonblocking
IO attempt of the operation, since we'll need to go async anyway. In
fact this is actively harmful, as reading from eg pipes won't return 0
to indicate EOF.

Cc: stable@vger.kernel.org # v5.7+
Reported-by: Benedikt Ames <wisp3rwind@posteo.eu>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2020-08-25 12:27:50 -06:00
parent 6b7898eb18
commit 9dab14b818
1 changed files with 9 additions and 1 deletions
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10
fs/io_uring.c
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@ -4889,12 +4889,20 @@ static bool io_arm_poll_handler(struct io_kiocb *req)
struct async_poll *apoll;
struct io_poll_table ipt;
__poll_t mask, ret;
int rw;
if (!req->file || !file_can_poll(req->file))
return false;
if (req->flags & REQ_F_POLLED)
return false;
if (!def->pollin && !def->pollout)
if (def->pollin)
rw = READ;
else if (def->pollout)
rw = WRITE;
else
return false;
/* if we can't nonblock try, then no point in arming a poll handler */
if (!io_file_supports_async(req->file, rw))
return false;
apoll = kmalloc(sizeof(*apoll), GFP_ATOMIC);