From: Jens Axboe <axboe@kernel.dk>
Date: Thu, 9 Jan 2020 14:52:28 +0000 (-0700)
Subject: io_uring: account fixed file references correctly in batch
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=10fef4bebf979bb705feed087611293d5864adfe;p=linux.git

io_uring: account fixed file references correctly in batch

We can't assume that the whole batch has fixed files in it. If it's a
mix, or none at all, then we can end up doing a ref put that either
messes up accounting, or causes an oops if we have no fixed files at
all.

Also ensure we free requests properly between inflight accounted and
normal requests.

Fixes: 82c721577011 ("io_uring: extend batch freeing to cover more cases")
Reported-by: Dmitrii Dolgov <9erthalion6@gmail.com>
Reported-by: Pavel Begunkov <asml.silence@gmail.com>
Tested-by: Dmitrii Dolgov <9erthalion6@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 50233efd94459..8a645a37b4c76 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1207,21 +1207,24 @@ struct req_batch {
 
 static void io_free_req_many(struct io_ring_ctx *ctx, struct req_batch *rb)
 {
+	int fixed_refs = rb->to_free;
+
 	if (!rb->to_free)
 		return;
 	if (rb->need_iter) {
 		int i, inflight = 0;
 		unsigned long flags;
 
+		fixed_refs = 0;
 		for (i = 0; i < rb->to_free; i++) {
 			struct io_kiocb *req = rb->reqs[i];
 
-			if (req->flags & REQ_F_FIXED_FILE)
+			if (req->flags & REQ_F_FIXED_FILE) {
 				req->file = NULL;
+				fixed_refs++;
+			}
 			if (req->flags & REQ_F_INFLIGHT)
 				inflight++;
-			else
-				rb->reqs[i] = NULL;
 			__io_req_aux_free(req);
 		}
 		if (!inflight)
@@ -1231,7 +1234,7 @@ static void io_free_req_many(struct io_ring_ctx *ctx, struct req_batch *rb)
 		for (i = 0; i < rb->to_free; i++) {
 			struct io_kiocb *req = rb->reqs[i];
 
-			if (req) {
+			if (req->flags & REQ_F_INFLIGHT) {
 				list_del(&req->inflight_entry);
 				if (!--inflight)
 					break;
@@ -1244,8 +1247,9 @@ static void io_free_req_many(struct io_ring_ctx *ctx, struct req_batch *rb)
 	}
 do_free:
 	kmem_cache_free_bulk(req_cachep, rb->to_free, rb->reqs);
+	if (fixed_refs)
+		percpu_ref_put_many(&ctx->file_data->refs, fixed_refs);
 	percpu_ref_put_many(&ctx->refs, rb->to_free);
-	percpu_ref_put_many(&ctx->file_data->refs, rb->to_free);
 	rb->to_free = rb->need_iter = 0;
 }