[PATCH] time: Fix off-by-one in compat settimeofday() usec validation

[PATCH] time: Fix off-by-one in compat settimeofday() usec validation

[Wang Yan]

The compat version of settimeofday() uses '>' instead of '>=' when
validating tv_usec against USEC_PER_SEC, allowing the value 1000000
to pass the check. After the subsequent conversion to nanoseconds
(tv_nsec *= NSEC_PER_USEC), this results in tv_nsec == NSEC_PER_SEC,
which violates the timespec invariant that tv_nsec must be strictly
less than NSEC_PER_SEC.

The native settimeofday() was already fixed in commit ce4abda5e126
("time: Fix off-by-one in settimeofday() usec validation"), but the
compat counterpart was missed.

Fix it by using '>=' to reject tv_usec values outside the valid
range [0, USEC_PER_SEC - 1].

Fixes: 5e0fb1b57bea ("y2038: time: avoid timespec usage in settimeofday()")
Signed-off-by: Wang Yan <wangyan01@kylinos.cn>
---
 kernel/time/time.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/time/time.c b/kernel/time/time.c
index 771cef87ad3b..0dd63a91e7c5 100644
--- a/kernel/time/time.c
+++ b/kernel/time/time.c
@@ -251,7 +251,7 @@ COMPAT_SYSCALL_DEFINE2(settimeofday, struct old_timeval32 __user *, tv,
 		    get_user(new_ts.tv_nsec, &tv->tv_usec))
 			return -EFAULT;
 
-		if (new_ts.tv_nsec > USEC_PER_SEC || new_ts.tv_nsec < 0)
+		if (new_ts.tv_nsec >= USEC_PER_SEC || new_ts.tv_nsec < 0)
 			return -EINVAL;
 
 		new_ts.tv_nsec *= NSEC_PER_USEC;
-- 
2.25.1

Re: [PATCH] time: Fix off-by-one in compat settimeofday() usec validation

[Arnd Bergmann]

On Mon, Jun 22, 2026, at 12:33, Wang Yan wrote:
> The compat version of settimeofday() uses '>' instead of '>=' when
> validating tv_usec against USEC_PER_SEC, allowing the value 1000000
> to pass the check. After the subsequent conversion to nanoseconds
> (tv_nsec *= NSEC_PER_USEC), this results in tv_nsec == NSEC_PER_SEC,
> which violates the timespec invariant that tv_nsec must be strictly
> less than NSEC_PER_SEC.
>
> The native settimeofday() was already fixed in commit ce4abda5e126
> ("time: Fix off-by-one in settimeofday() usec validation"), but the
> compat counterpart was missed.
>
> Fix it by using '>=' to reject tv_usec values outside the valid
> range [0, USEC_PER_SEC - 1].
>
> Fixes: 5e0fb1b57bea ("y2038: time: avoid timespec usage in settimeofday()")
> Signed-off-by: Wang Yan <wangyan01@kylinos.cn>

Acked-by: Arnd Bergmann <arnd@arndb.de>

probably also

Cc: stable@vger.kernel.org

[tip: timers/urgent] time: Fix off-by-one in compat settimeofday() usec validation

[tip-bot2 for Wang Yan]

The following commit has been merged into the timers/urgent branch of tip:

Commit-ID:     269f2b43fae692d1f3988c9f888a6301aa537b82
Gitweb:        https://git.kernel.org/tip/269f2b43fae692d1f3988c9f888a6301aa537b82
Author:        Wang Yan <wangyan01@kylinos.cn>
AuthorDate:    Mon, 22 Jun 2026 18:33:48 +08:00
Committer:     Thomas Gleixner <tglx@kernel.org>
CommitterDate: Mon, 22 Jun 2026 13:20:20 +02:00

time: Fix off-by-one in compat settimeofday() usec validation

The compat version of settimeofday() uses '>' instead of '>=' when
validating tv_usec against USEC_PER_SEC, allowing the value 1000000 to pass
the check. After the subsequent conversion to nanoseconds (tv_nsec *=
NSEC_PER_USEC), this results in tv_nsec == NSEC_PER_SEC, which violates the
timespec invariant that tv_nsec must be strictly less than NSEC_PER_SEC.

The native settimeofday() was already fixed in commit ce4abda5e126 ("time:
Fix off-by-one in settimeofday() usec validation"), but the compat
counterpart was missed.

Fix it by using '>=' to reject tv_usec values outside the valid range [0,
USEC_PER_SEC - 1].

Fixes: 5e0fb1b57bea ("y2038: time: avoid timespec usage in settimeofday()")
Signed-off-by: Wang Yan <wangyan01@kylinos.cn>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260622103348.120255-1-wangyan01@kylinos.cn
---
 kernel/time/time.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/time/time.c b/kernel/time/time.c
index 771cef8..0dd63a9 100644
--- a/kernel/time/time.c
+++ b/kernel/time/time.c
@@ -251,7 +251,7 @@ COMPAT_SYSCALL_DEFINE2(settimeofday, struct old_timeval32 __user *, tv,
 		    get_user(new_ts.tv_nsec, &tv->tv_usec))
 			return -EFAULT;
 
-		if (new_ts.tv_nsec > USEC_PER_SEC || new_ts.tv_nsec < 0)
+		if (new_ts.tv_nsec >= USEC_PER_SEC || new_ts.tv_nsec < 0)
 			return -EINVAL;
 
 		new_ts.tv_nsec *= NSEC_PER_USEC;