From: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
Date: Mon, 1 Sep 2025 08:48:48 +0000 (+0300)
Subject: fs/ntfs3: Support timestamps prior to epoch
X-Git-Tag: v6.19-rc1~160^2~25
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5180138604323895b5c291eca6aa7c20be494ade;p=thirdparty%2Fkernel%2Flinux.git

fs/ntfs3: Support timestamps prior to epoch

Before it used an unsigned 64-bit type, which prevented proper handling
of timestamps earlier than 1970-01-01. Switch to a signed 64-bit type to
support pre-epoch timestamps. The issue was caught by xfstests.

Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
---

diff --git a/fs/ntfs3/ntfs_fs.h b/fs/ntfs3/ntfs_fs.h
index 630128716ea73..2649fbe16669d 100644
--- a/fs/ntfs3/ntfs_fs.h
+++ b/fs/ntfs3/ntfs_fs.h
@@ -979,11 +979,12 @@ static inline __le64 kernel2nt(const struct timespec64 *ts)
  */
 static inline void nt2kernel(const __le64 tm, struct timespec64 *ts)
 {
-	u64 t = le64_to_cpu(tm) - _100ns2seconds * SecondsToStartOf1970;
+	s32 t32;
+	/* use signed 64 bit to support timestamps prior to epoch. xfstest 258. */
+	s64 t = le64_to_cpu(tm) - _100ns2seconds * SecondsToStartOf1970;
 
-	// WARNING: do_div changes its first argument(!)
-	ts->tv_nsec = do_div(t, _100ns2seconds) * 100;
-	ts->tv_sec = t;
+	ts->tv_sec = div_s64_rem(t, _100ns2seconds, &t32);
+	ts->tv_nsec = t32 * 100;
 }
 
 static inline struct ntfs_sb_info *ntfs_sb(struct super_block *sb)