linux-kernel - [PATCH AUTOSEL 4.14 3/5] cifs: destage any unwritten data to the server before calling copychunk

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]

Message-Id: <20220426190258.2351902-3-sashal@kernel.org>
Date:   Tue, 26 Apr 2022 15:02:54 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Ronnie Sahlberg <lsahlber@...hat.com>,
        Xiaoli Feng <xifeng@...hat.com>,
        Steve French <stfrench@...rosoft.com>,
        Sasha Levin <sashal@...nel.org>, sfrench@...ba.org,
        linux-cifs@...r.kernel.org, samba-technical@...ts.samba.org
Subject: [PATCH AUTOSEL 4.14 3/5] cifs: destage any unwritten data to the server before calling copychunk_write

From: Ronnie Sahlberg <lsahlber@...hat.com>

[ Upstream commit f5d0f921ea362636e4a2efb7c38d1ead373a8700 ]

because the copychunk_write might cover a region of the file that has not yet
been sent to the server and thus fail.

A simple way to reproduce this is:
truncate -s 0 /mnt/testfile; strace -f -o x -ttT xfs_io -i -f -c 'pwrite 0k 128k' -c 'fcollapse 16k 24k' /mnt/testfile

the issue is that the 'pwrite 0k 128k' becomes rearranged on the wire with
the 'fcollapse 16k 24k' due to write-back caching.

fcollapse is implemented in cifs.ko as a SMB2 IOCTL(COPYCHUNK_WRITE) call
and it will fail serverside since the file is still 0b in size serverside
until the writes have been destaged.
To avoid this we must ensure that we destage any unwritten data to the
server before calling COPYCHUNK_WRITE.

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1997373
Reported-by: Xiaoli Feng <xifeng@...hat.com>
Signed-off-by: Ronnie Sahlberg <lsahlber@...hat.com>
Signed-off-by: Steve French <stfrench@...rosoft.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/cifs/smb2ops.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index ba56c00f2650..3280a801b1d7 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -855,9 +855,17 @@ smb2_copychunk_range(const unsigned int xid,
 	int chunks_copied = 0;
 	bool chunk_sizes_updated = false;
 	ssize_t bytes_written, total_bytes_written = 0;
+	struct inode *inode;
 
 	pcchunk = kmalloc(sizeof(struct copychunk_ioctl), GFP_KERNEL);
 
+	/*
+	 * We need to flush all unwritten data before we can send the
+	 * copychunk ioctl to the server.
+	 */
+	inode = d_inode(trgtfile->dentry);
+	filemap_write_and_wait(inode->i_mapping);
+
 	if (pcchunk == NULL)
 		return -ENOMEM;
 
-- 
2.35.1