io_uring: run __io_sq_thread() with the initial creds from io_uring_setup()

With IORING_SETUP_ATTACH_WQ we should let __io_sq_thread() use the
initial creds from each ctx.

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 8c74c77..4d3333c 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -380,6 +380,7 @@ struct io_ring_ctx {
        /* Only used for accounting purposes */
        struct mm_struct        *mm_account;
 
+       const struct cred       *sq_creds;      /* cred used for __io_sq_thread() */
        struct io_sq_data       *sq_data;       /* if using sq thread polling */
 
        struct wait_queue_head  sqo_sq_wait;
@@ -6719,7 +6720,13 @@ static int io_sq_thread(void *data)
                sqt_spin = false;
                cap_entries = !list_is_singular(&sqd->ctx_list);
                list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) {
+                       const struct cred *creds = NULL;
+
+                       if (ctx->sq_creds != current_cred())
+                               creds = override_creds(ctx->sq_creds);
                        ret = __io_sq_thread(ctx, cap_entries);
+                       if (creds)
+                               revert_creds(creds);
                        if (!sqt_spin && (ret > 0 || !list_empty(&ctx->iopoll_list)))
                                sqt_spin = true;
                }
@@ -7152,6 +7159,8 @@ static void io_sq_thread_finish(struct io_ring_ctx *ctx)
 
                io_put_sq_data(sqd);
                ctx->sq_data = NULL;
+               if (ctx->sq_creds)
+                       put_cred(ctx->sq_creds);
        }
 }
 
@@ -7890,6 +7899,7 @@ static int io_sq_offload_create(struct io_ring_ctx *ctx,
                        goto err;
                }
 
+               ctx->sq_creds = get_current_cred();
                ctx->sq_data = sqd;
                io_sq_thread_park(sqd);
                mutex_lock(&sqd->ctx_lock);