FAILED: patch "[PATCH] fuse: release pipe buf after last use" failed to apply to 4.4-stable tree

FAILED: patch "[PATCH] fuse: release pipe buf after last use" failed to apply to 4.4-stable tree

[gregkh]

The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 473441720c8616dfaf4451f9c7ea14f0eb5e5d65 Mon Sep 17 00:00:00 2001
From: Miklos Szeredi <mszeredi@redhat.com>
Date: Thu, 25 Nov 2021 14:05:18 +0100
Subject: [PATCH] fuse: release pipe buf after last use

Checking buf->flags should be done before the pipe_buf_release() is called
on the pipe buffer, since releasing the buffer might modify the flags.

This is exactly what page_cache_pipe_buf_release() does, and which results
in the same VM_BUG_ON_PAGE(PageLRU(page)) that the original patch was
trying to fix.

Reported-by: Justin Forbes <jmforbes@linuxtx.org>
Fixes: 712a951025c0 ("fuse: fix page stealing")
Cc: <stable@vger.kernel.org> # v2.6.35
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 79f7eda49e06..cd54a529460d 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -847,17 +847,17 @@ static int fuse_try_move_page(struct fuse_copy_state *cs, struct page **pagep)
 
 	replace_page_cache_page(oldpage, newpage);
 
+	get_page(newpage);
+
+	if (!(buf->flags & PIPE_BUF_FLAG_LRU))
+		lru_cache_add(newpage);
+
 	/*
 	 * Release while we have extra ref on stolen page.  Otherwise
 	 * anon_pipe_buf_release() might think the page can be reused.
 	 */
 	pipe_buf_release(cs->pipe, buf);
 
-	get_page(newpage);
-
-	if (!(buf->flags & PIPE_BUF_FLAG_LRU))
-		lru_cache_add(newpage);
-
 	err = 0;
 	spin_lock(&cs->req->waitq.lock);
 	if (test_bit(FR_ABORTED, &cs->req->flags))

Re: FAILED: patch "[PATCH] fuse: release pipe buf after last use" failed to apply to 4.4-stable tree

[Miklos Szeredi]

[-- Attachment #1: Type: text/plain, Size: 585 bytes --]

On Sat, Nov 27, 2021 at 2:11 PM <gregkh@linuxfoundation.org> wrote:
>
>
> The patch below does not apply to the 4.4-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@vger.kernel.org>.


Hi Greg,

Attaching the backport of this patch against 4.4.292 + "fuse: fix page
stealing".

The latter has been dropped from 4.4, but together with this backport
should be good to go:

  stable-queue.git#c7f34b89ddfe^:queue-4.4/fuse-fix-page-stealing.patch

Thanks,
Miklos

[-- Attachment #2: fuse-release-pipe-buf-after-last-use-4.4.patch --]
[-- Type: text/x-patch, Size: 1705 bytes --]

From 753e333e86f0e41860adf34bf4ffcf10b2188b9d Mon Sep 17 00:00:00 2001
From: Miklos Szeredi <mszeredi@redhat.com>
Date: Thu, 25 Nov 2021 14:05:18 +0100
Subject: [PATCH] fuse: release pipe buf after last use

Checking buf->flags should be done before the pipe_buf_release() is called
on the pipe buffer, since releasing the buffer might modify the flags.

This is exactly what page_cache_pipe_buf_release() does, and which results
in the same VM_BUG_ON_PAGE(PageLRU(page)) that the original patch was
trying to fix.

Reported-by: Justin Forbes <jmforbes@linuxtx.org>
Fixes: 712a951025c0 ("fuse: fix page stealing")
Cc: <stable@vger.kernel.org> # v2.6.35
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
(cherry picked from commit 473441720c8616dfaf4451f9c7ea14f0eb5e5d65)
---
 fs/fuse/dev.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 75fad41bc6e1..dc705e4be350 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -922,6 +922,11 @@ static int fuse_try_move_page(struct fuse_copy_state *cs, struct page **pagep)
 		return err;
 	}
 
+	page_cache_get(newpage);
+
+	if (!(buf->flags & PIPE_BUF_FLAG_LRU))
+		lru_cache_add_file(newpage);
+
 	/*
 	 * Release while we have extra ref on stolen page.  Otherwise
 	 * anon_pipe_buf_release() might think the page can be reused.
@@ -929,11 +934,6 @@ static int fuse_try_move_page(struct fuse_copy_state *cs, struct page **pagep)
 	buf->ops->release(cs->pipe, buf);
 	buf->ops = NULL;
 
-	page_cache_get(newpage);
-
-	if (!(buf->flags & PIPE_BUF_FLAG_LRU))
-		lru_cache_add_file(newpage);
-
 	err = 0;
 	spin_lock(&cs->req->waitq.lock);
 	if (test_bit(FR_ABORTED, &cs->req->flags))
-- 
2.31.1

Re: FAILED: patch "[PATCH] fuse: release pipe buf after last use" failed to apply to 4.4-stable tree

[Greg Kroah-Hartman]

On Mon, Nov 29, 2021 at 05:10:41PM +0100, Miklos Szeredi wrote:
> On Sat, Nov 27, 2021 at 2:11 PM <gregkh@linuxfoundation.org> wrote:
> >
> >
> > The patch below does not apply to the 4.4-stable tree.
> > If someone wants it applied there, or to any other stable or longterm
> > tree, then please email the backport, including the original git commit
> > id to <stable@vger.kernel.org>.
> 
> 
> Hi Greg,
> 
> Attaching the backport of this patch against 4.4.292 + "fuse: fix page
> stealing".
> 
> The latter has been dropped from 4.4, but together with this backport
> should be good to go:
> 
>   stable-queue.git#c7f34b89ddfe^:queue-4.4/fuse-fix-page-stealing.patch

Now queued up, thanks.

greg k-h