io_uring: limit registration w/ SINGLE_ISSUER

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@vger.kernel.org> # 6.0
Fixes: 97bbdc06a444 ("io_uring: add IORING_SETUP_SINGLE_ISSUER")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/f52a6a9c8a8990d4a831f73c0571e7406aac2bba.1664237592.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index fe6ef64..63f6ce5 100644 (file)
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -3890,6 +3890,9 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
        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;