Patch "io_uring: fix linked deferred ->files cancellation" has been added to the 5.8-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    io_uring: fix linked deferred ->files cancellation

to the 5.8-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     io_uring-fix-linked-deferred-files-cancellation.patch
and it can be found in the queue-5.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit add036bcf863627747ac09444cd5727791348fb0
Author: Pavel Begunkov <asml.silence@xxxxxxxxx>
Date:   Sun Sep 6 00:45:15 2020 +0300

    io_uring: fix linked deferred ->files cancellation
    
    [ Upstream commit c127a2a1b7baa5eb40a7e2de4b7f0c51ccbbb2ef ]
    
    While looking for ->files in ->defer_list, consider that requests there
    may actually be links.
    
    Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
    Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 5f627194d0920..d05023ca74bdc 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -7601,6 +7601,28 @@ static bool io_match_link(struct io_kiocb *preq, struct io_kiocb *req)
 	return false;
 }
 
+static inline bool io_match_files(struct io_kiocb *req,
+				       struct files_struct *files)
+{
+	return (req->flags & REQ_F_WORK_INITIALIZED) && req->work.files == files;
+}
+
+static bool io_match_link_files(struct io_kiocb *req,
+				struct files_struct *files)
+{
+	struct io_kiocb *link;
+
+	if (io_match_files(req, files))
+		return true;
+	if (req->flags & REQ_F_LINK_HEAD) {
+		list_for_each_entry(link, &req->link_list, link_list) {
+			if (io_match_files(link, files))
+				return true;
+		}
+	}
+	return false;
+}
+
 /*
  * We're looking to cancel 'req' because it's holding on to our files, but
  * 'req' could be a link to another request. See if it is, and cancel that
@@ -7683,8 +7705,7 @@ static void io_cancel_defer_files(struct io_ring_ctx *ctx,
 
 	spin_lock_irq(&ctx->completion_lock);
 	list_for_each_entry_reverse(req, &ctx->defer_list, list) {
-		if ((req->flags & REQ_F_WORK_INITIALIZED)
-			&& req->work.files == files) {
+		if (io_match_link_files(req, files)) {
 			list_cut_position(&list, &ctx->defer_list, &req->list);
 			break;
 		}