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: [e-mail]
Fixes: 44d282796f81 ("io_uring: only allow submit from owning task")
Reported-by: Andres Freund <[e-mail]>
Signed-off-by: Jens Axboe <[e-mail]>

fs/io_uring.c

···
 	} 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 */