From b092b3efc7cb239b6f33bb97da0f8812680e1046 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Thu, 22 Apr 2021 16:52:32 +0200
Subject: [PATCH] cifs: Fix race between hole punch and page fault
Git-commit: b092b3efc7cb239b6f33bb97da0f8812680e1046
Patch-mainline: v5.15-rc1
References: bsc#1194346
Cifs has a following race between hole punching and page fault:
CPU1 CPU2
smb3_fallocate()
smb3_punch_hole()
truncate_pagecache_range()
filemap_fault()
- loads old data into the
page cache
SMB2_ioctl(..., FSCTL_SET_ZERO_DATA, ...)
And now we have stale data in the page cache. Fix the problem by locking
out faults (as well as reads) using mapping->invalidate_lock while hole
punch is running.
Cc: Steve French <sfrench@samba.org>
Cc: linux-cifs@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
Acked-by: Jan Kara <jack@suse.cz>
---
fs/cifs/smb2ops.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index e4c8f603dd58..458c546ce8cd 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -3588,6 +3588,7 @@ static long smb3_punch_hole(struct file *file, struct cifs_tcon *tcon,
return rc;
}
+ filemap_invalidate_lock(inode->i_mapping);
/*
* We implement the punch hole through ioctl, so we need remove the page
* caches first, otherwise the data may be inconsistent with the server.
@@ -3605,6 +3606,7 @@ static long smb3_punch_hole(struct file *file, struct cifs_tcon *tcon,
sizeof(struct file_zero_data_information),
CIFSMaxBufSize, NULL, NULL);
free_xid(xid);
+ filemap_invalidate_unlock(inode->i_mapping);
return rc;
}
--
2.31.1