Revert "io_uring: only allow submit from owning task"

This ends up being too restrictive for tasks that willingly fork and
share the ring between forks. Andres reports that this breaks his
postgresql work. Since we're close to 5.5 release, revert this change
for now.

Cc: [email protected]
Fixes: 44d2827 ("io_uring: only allow submit from owning task")
Reported-by: Andres Freund <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

Author: axboe

fs/io_uring.c

@@ -5161,12 +5161,6 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
 	} else if (to_submit) {
 		struct mm_struct *cur_mm;
 
-		if (current->mm != ctx->sqo_mm ||
-		    current_cred() != ctx->creds) {
-			ret = -EPERM;
-			goto out;
-		}
-
 		to_submit = min(to_submit, ctx->sq_entries);
 		mutex_lock(&ctx->uring_lock);
 		/* already have mm, so io_submit_sqes() won't try to grab it */