[PATCH AUTOSEL 6.8 08/24] udf: udftime: prevent overflow in udf_disk_stamp_to_time()

[Sasha Levin <sashal@kernel.org>]

From: Roman Smirnov <r.smirnov@omp.ru>

[ Upstream commit 3b84adf460381169c085e4bc09e7b57e9e16db0a ]

An overflow can occur in a situation where src.centiseconds
takes the value of 255. This situation is unlikely, but there
is no validation check anywere in the code.

Found by Linux Verification Center (linuxtesting.org) with Svace.

Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Roman Smirnov <r.smirnov@omp.ru>
Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Signed-off-by: Jan Kara <jack@suse.cz>
Message-Id: <20240327132755.13945-1-r.smirnov@omp.ru>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/udf/udftime.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/fs/udf/udftime.c b/fs/udf/udftime.c
index 758163af39c26..78ecc633606fb 100644
--- a/fs/udf/udftime.c
+++ b/fs/udf/udftime.c
@@ -46,13 +46,18 @@ udf_disk_stamp_to_time(struct timespec64 *dest, struct timestamp src)
 	dest->tv_sec = mktime64(year, src.month, src.day, src.hour, src.minute,
 			src.second);
 	dest->tv_sec -= offset * 60;
-	dest->tv_nsec = 1000 * (src.centiseconds * 10000 +
-			src.hundredsOfMicroseconds * 100 + src.microseconds);
+
 	/*
 	 * Sanitize nanosecond field since reportedly some filesystems are
 	 * recorded with bogus sub-second values.
 	 */
-	dest->tv_nsec %= NSEC_PER_SEC;
+	if (src.centiseconds < 100 && src.hundredsOfMicroseconds < 100 &&
+	    src.microseconds < 100) {
+		dest->tv_nsec = 1000 * (src.centiseconds * 10000 +
+			src.hundredsOfMicroseconds * 100 + src.microseconds);
+	} else {
+		dest->tv_nsec = 0;
+	}
 }
 
 void
-- 
2.43.0