linux-kernel - [PATCH 5.3 095/148] 9p: avoid attaching writeback

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Thu, 10 Oct 2019 10:35:56 +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, Chengguang Xu <cgxu519@...o.com.cn>,
        Dominique Martinet <dominique.martinet@....fr>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.3 095/148] 9p: avoid attaching writeback_fid on mmap with type PRIVATE

From: Chengguang Xu <cgxu519@...o.com.cn>

[ Upstream commit c87a37ebd40b889178664c2c09cc187334146292 ]

Currently on mmap cache policy, we always attach writeback_fid
whether mmap type is SHARED or PRIVATE. However, in the use case
of kata-container which combines 9p(Guest OS) with overlayfs(Host OS),
this behavior will trigger overlayfs' copy-up when excute command
inside container.

Link: http://lkml.kernel.org/r/20190820100325.10313-1-cgxu519@zoho.com.cn
Signed-off-by: Chengguang Xu <cgxu519@...o.com.cn>
Signed-off-by: Dominique Martinet <dominique.martinet@....fr>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/9p/vfs_file.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/9p/vfs_file.c b/fs/9p/vfs_file.c
index 4cc966a31cb37..fe7f0bd2048e4 100644
--- a/fs/9p/vfs_file.c
+++ b/fs/9p/vfs_file.c
@@ -513,6 +513,7 @@ v9fs_mmap_file_mmap(struct file *filp, struct vm_area_struct *vma)
 	v9inode = V9FS_I(inode);
 	mutex_lock(&v9inode->v_mutex);
 	if (!v9inode->writeback_fid &&
+	    (vma->vm_flags & VM_SHARED) &&
 	    (vma->vm_flags & VM_WRITE)) {
 		/*
 		 * clone a fid and add it to writeback_fid
@@ -614,6 +615,8 @@ static void v9fs_mmap_vm_close(struct vm_area_struct *vma)
 			(vma->vm_end - vma->vm_start - 1),
 	};
 
+	if (!(vma->vm_flags & VM_SHARED))
+		return;
 
 	p9_debug(P9_DEBUG_VFS, "9p VMA close, %p, flushing", vma);
 
-- 
2.20.1