[PATCH 6.0 017/862] io_uring: limit registration w/ SINGLE_ISSUER

[Greg Kroah-Hartman]

From: Pavel Begunkov <asml.silence@xxxxxxxxx>

commit d7cce96c449e35bbfd41e830b341b95973891eed upstream.

IORING_SETUP_SINGLE_ISSUER restricts what tasks can submit requests.
Extend it to registration as well, so non-owning task can't do
registrations. It's not necessary at the moment but might be useful in
the future.

Cc: <stable@xxxxxxxxxxxxxxx> # 6.0
Fixes: 97bbdc06a444 ("io_uring: add IORING_SETUP_SINGLE_ISSUER")
Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
Link: https://lore.kernel.org/r/f52a6a9c8a8990d4a831f73c0571e7406aac2bba.1664237592.git.asml.silence@xxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 io_uring/io_uring.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -3710,6 +3710,9 @@ static int __io_uring_register(struct io
 	if (WARN_ON_ONCE(percpu_ref_is_dying(&ctx->refs)))
 		return -ENXIO;
 
+	if (ctx->submitter_task && ctx->submitter_task != current)
+		return -EEXIST;
+
 	if (ctx->restricted) {
 		if (opcode >= IORING_REGISTER_LAST)
 			return -EINVAL;