io-wq: always track creds for async issue

If we go async with a request, grab the creds that the task currently has
assigned and make sure that the async side switches to them. This is
handled in the same way that we do for registered personalities.
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io-wq.h

@@ -79,8 +79,8 @@ static inline void wq_list_del(struct io_wq_work_list *list,
 
 struct io_wq_work {
 	struct io_wq_work_node list;
+	const struct cred *creds;
 	unsigned flags;
-	unsigned short personality;
 };
 
 static inline struct io_wq_work *wq_next_work(struct io_wq_work *work)

fs/io_uring.c

@@ -1183,6 +1183,9 @@ static void io_prep_async_work(struct io_kiocb *req)
 	const struct io_op_def *def = &io_op_defs[req->opcode];
 	struct io_ring_ctx *ctx = req->ctx;
 
+	if (!req->work.creds)
+		req->work.creds = get_current_cred();
+
 	if (req->flags & REQ_F_FORCE_ASYNC)
 		req->work.flags |= IO_WQ_WORK_CONCURRENT;
 
@@ -1648,6 +1651,10 @@ static void io_dismantle_req(struct io_kiocb *req)
 		io_put_file(req, req->file, (req->flags & REQ_F_FIXED_FILE));
 	if (req->fixed_rsrc_refs)
 		percpu_ref_put(req->fixed_rsrc_refs);
+	if (req->work.creds) {
+		put_cred(req->work.creds);
+		req->work.creds = NULL;
+	}
 
 	if (req->flags & REQ_F_INFLIGHT) {
 		struct io_ring_ctx *ctx = req->ctx;
@@ -5916,18 +5923,8 @@ static int io_issue_sqe(struct io_kiocb *req, unsigned int issue_flags)
 	const struct cred *creds = NULL;
 	int ret;
 
-	if (req->work.personality) {
-		const struct cred *new_creds;
-
-		if (!(issue_flags & IO_URING_F_NONBLOCK))
-			mutex_lock(&ctx->uring_lock);
-		new_creds = idr_find(&ctx->personality_idr, req->work.personality);
-		if (!(issue_flags & IO_URING_F_NONBLOCK))
-			mutex_unlock(&ctx->uring_lock);
-		if (!new_creds)
-			return -EINVAL;
-		creds = override_creds(new_creds);
-	}
+	if (req->work.creds && req->work.creds != current_cred())
+		creds = override_creds(req->work.creds);
 
 	switch (req->opcode) {
 	case IORING_OP_NOP:
@@ -6291,7 +6288,7 @@ static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req,
 {
 	struct io_submit_state *state;
 	unsigned int sqe_flags;
-	int ret = 0;
+	int personality, ret = 0;
 
 	req->opcode = READ_ONCE(sqe->opcode);
 	/* same numerical values with corresponding REQ_F_*, safe to copy */
@@ -6324,8 +6321,16 @@ static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req,
 		return -EOPNOTSUPP;
 
 	req->work.list.next = NULL;
+	personality = READ_ONCE(sqe->personality);
+	if (personality) {
+		req->work.creds = idr_find(&ctx->personality_idr, personality);
+		if (!req->work.creds)
+			return -EINVAL;
+		get_cred(req->work.creds);
+	} else {
+		req->work.creds = NULL;
+	}
 	req->work.flags = 0;
-	req->work.personality = READ_ONCE(sqe->personality);
 	state = &ctx->submit_state;
 
 	/*