linux-kernel - [PATCH 1/3] hfs: stop using timespec based interfaces

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Message-Id: <20180619160223.4108556-1-arnd@arndb.de>
Date:   Tue, 19 Jun 2018 18:02:07 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Al Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     y2038@...ts.linaro.org, Arnd Bergmann <arnd@...db.de>,
        Jeff Layton <jlayton@...hat.com>, Jan Kara <jack@...e.cz>,
        Deepa Dinamani <deepa.kernel@...il.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 1/3] hfs: stop using timespec based interfaces

The native HFS timestamps overflow in year 2040, two years after the Unix
y2038 overflow. However, the way that the conversion between on-disk
timestamps and in-kernel timestamps was implemented, 64-bit machines
actually ended up converting negative UTC timestamps (1902 through 1969)
into times between 2038 and 2106.

Rather than making all machines faithfully represent timestamps in the
ancient past but break after 2040, this changes the file system to
always use the unsigned UTC interpretation, reading back times between
1970 and 2106.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 fs/hfs/hfs_fs.h | 6 ++++--
 fs/hfs/inode.c  | 4 ++--
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/fs/hfs/hfs_fs.h b/fs/hfs/hfs_fs.h
index 6d0783e2e276..ff432931a5b1 100644
--- a/fs/hfs/hfs_fs.h
+++ b/fs/hfs/hfs_fs.h
@@ -245,6 +245,8 @@ extern void hfs_mark_mdb_dirty(struct super_block *sb);
  *	Unix:	unsigned lil-endian since 00:00 GMT, Jan. 1, 1970
  *	mac:	unsigned big-endian since 00:00 GMT, Jan. 1, 1904
  *
+ * We treat all timestamps before 1970 as times after 2038, so this
+ * actually works until year 2106
  */
 #define __hfs_u_to_mtime(sec)	cpu_to_be32(sec + 2082844800U - sys_tz.tz_minuteswest * 60)
 #define __hfs_m_to_utime(sec)	(be32_to_cpu(sec) - 2082844800U  + sys_tz.tz_minuteswest * 60)
@@ -252,9 +254,9 @@ extern void hfs_mark_mdb_dirty(struct super_block *sb);
 #define HFS_I(inode)	(container_of(inode, struct hfs_inode_info, vfs_inode))
 #define HFS_SB(sb)	((struct hfs_sb_info *)(sb)->s_fs_info)
 
-#define hfs_m_to_utime(time)	(struct timespec){ .tv_sec = __hfs_m_to_utime(time) }
+#define hfs_m_to_utime(time)	(struct timespec64){ .tv_sec = __hfs_m_to_utime(time) }
 #define hfs_u_to_mtime(time)	__hfs_u_to_mtime((time).tv_sec)
-#define hfs_mtime()		__hfs_u_to_mtime(get_seconds())
+#define hfs_mtime()		__hfs_u_to_mtime(ktime_get_real_seconds())
 
 static inline const char *hfs_mdb_name(struct super_block *sb)
 {
diff --git a/fs/hfs/inode.c b/fs/hfs/inode.c
index 2a16111d312f..b3309b83371a 100644
--- a/fs/hfs/inode.c
+++ b/fs/hfs/inode.c
@@ -351,7 +351,7 @@ static int hfs_read_inode(struct inode *inode, void *data)
 		inode->i_mode &= ~hsb->s_file_umask;
 		inode->i_mode |= S_IFREG;
 		inode->i_ctime = inode->i_atime = inode->i_mtime =
-				timespec_to_timespec64(hfs_m_to_utime(rec->file.MdDat));
+				hfs_m_to_utime(rec->file.MdDat);
 		inode->i_op = &hfs_file_inode_operations;
 		inode->i_fop = &hfs_file_operations;
 		inode->i_mapping->a_ops = &hfs_aops;
@@ -362,7 +362,7 @@ static int hfs_read_inode(struct inode *inode, void *data)
 		HFS_I(inode)->fs_blocks = 0;
 		inode->i_mode = S_IFDIR | (S_IRWXUGO & ~hsb->s_dir_umask);
 		inode->i_ctime = inode->i_atime = inode->i_mtime =
-				timespec_to_timespec64(hfs_m_to_utime(rec->dir.MdDat));
+				hfs_m_to_utime(rec->dir.MdDat);
 		inode->i_op = &hfs_dir_inode_operations;
 		inode->i_fop = &hfs_dir_operations;
 		break;
-- 
2.9.0