linux-kernel - [PATCH 5.11 02/41] ovl: fix reference counting in ovl

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Date:   Mon, 26 Apr 2021 09:29:49 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Christian König <christian.koenig@....com>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Jan Harkes <jaharkes@...cmu.edu>,
        Miklos Szeredi <miklos@...redi.hu>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 5.11 02/41] ovl: fix reference counting in ovl_mmap error path

From: Christian König <christian.koenig@....com>

commit 2896900e22f8212606a1837d89a6bbce314ceeda upstream.

mmap_region() now calls fput() on the vma->vm_file.

Fix this by using vma_set_file() so it doesn't need to be handled
manually here any more.

Link: https://lkml.kernel.org/r/20210421132012.82354-2-christian.koenig@amd.com
Fixes: 1527f926fd04 ("mm: mmap: fix fput in error path v2")
Signed-off-by: Christian König <christian.koenig@....com>
Reviewed-by: Daniel Vetter <daniel.vetter@...ll.ch>
Cc: Jan Harkes <jaharkes@...cmu.edu>
Cc: Miklos Szeredi <miklos@...redi.hu>
Cc: Jason Gunthorpe <jgg@...pe.ca>
Cc: <stable@...r.kernel.org>	[5.11+]
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/overlayfs/file.c |   11 +----------
 1 file changed, 1 insertion(+), 10 deletions(-)

--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -430,20 +430,11 @@ static int ovl_mmap(struct file *file, s
 	if (WARN_ON(file != vma->vm_file))
 		return -EIO;
 
-	vma->vm_file = get_file(realfile);
+	vma_set_file(vma, realfile);
 
 	old_cred = ovl_override_creds(file_inode(file)->i_sb);
 	ret = call_mmap(vma->vm_file, vma);
 	revert_creds(old_cred);
-
-	if (ret) {
-		/* Drop reference count from new vm_file value */
-		fput(realfile);
-	} else {
-		/* Drop reference count from previous vm_file value */
-		fput(file);
-	}
-
 	ovl_file_accessed(file);
 
 	return ret;