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From:   zhengbin <zhengbin13@huawei.com>
To:     <phillip@squashfs.org.uk>, <linux-kernel@vger.kernel.org>
CC:     <houtao1@huawei.com>, <zhaohongjiang@huawei.com>,
        <zhengbin13@huawei.com>
Subject: [PATCH] squashfs: fix mtime underflow on 64 bit system
Date:   Thu, 17 Jan 2019 16:21:48 +0800
Message-ID: <20190117082148.129347-1-zhengbin13@huawei.com>
MIME-Version: 1.0
Content-Type: text/plain
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

If we change the file mtime to 1969, mksquashfs and mount,
the atime/mtime of this file will be underflow. The reason is
treating timestamps with the high bit set as positive
times(before 1970), which should be set as negative times
just like on 32 bit system. After this, the poissble range
of timestamps will be 1901-2038(prev is 1970-2106) on 64
bit system.

Signed-off-by: zhengbin <zhengbin13@huawei.com>
---
 fs/squashfs/inode.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/squashfs/inode.c b/fs/squashfs/inode.c
index e9793b1e49a5..03a6ef77a2d2 100644
--- a/fs/squashfs/inode.c
+++ b/fs/squashfs/inode.c
@@ -72,7 +72,7 @@ static int squashfs_new_inode(struct super_block *sb, struct inode *inode,
 	i_uid_write(inode, i_uid);
 	i_gid_write(inode, i_gid);
 	inode->i_ino = le32_to_cpu(sqsh_ino->inode_number);
-	inode->i_mtime.tv_sec = le32_to_cpu(sqsh_ino->mtime);
+	inode->i_mtime.tv_sec = (signed int)le32_to_cpu(sqsh_ino->mtime);
 	inode->i_atime.tv_sec = inode->i_mtime.tv_sec;
 	inode->i_ctime.tv_sec = inode->i_mtime.tv_sec;
 	inode->i_mode = le16_to_cpu(sqsh_ino->mode);
--
2.16.2.dirty