[PATCH 5.15 198/277] io_uring: dont touch scm_fp_list after queueing skb

[Greg Kroah-Hartman]

From: Pavel Begunkov <asml.silence@xxxxxxxxx>

[ Upstream commit a07211e3001435fe8591b992464cd8d5e3c98c5a ]

It's safer to not touch scm_fp_list after we queued an skb to which it
was assigned, there might be races lurking if we screw subtle sync
guarantees on the io_uring side.

Fixes: 6b06314c47e14 ("io_uring: add file set registration")
Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 fs/io_uring.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 21823d1e91de..2faa558778ba 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -8126,8 +8126,12 @@ static int __io_sqe_files_scm(struct io_ring_ctx *ctx, int nr, int offset)
 		refcount_add(skb->truesize, &sk->sk_wmem_alloc);
 		skb_queue_head(&sk->sk_receive_queue, skb);
 
-		for (i = 0; i < nr_files; i++)
-			fput(fpl->fp[i]);
+		for (i = 0; i < nr; i++) {
+			struct file *file = io_file_from_index(ctx, i + offset);
+
+			if (file)
+				fput(file);
+		}
 	} else {
 		kfree_skb(skb);
 		free_uid(fpl->user);
-- 
2.35.1