From cb47755725da7b90fecbb2aa82ac3b24a7adb89b Mon Sep 17 00:00:00 2001
From: Zeng Tao <prime.zeng@hisilicon.com>
Date: Tue, 1 Sep 2020 17:30:13 +0800
Subject: [PATCH] time: Prevent undefined behaviour in timespec64_to_ns()
Git-commit: cb47755725da7b90fecbb2aa82ac3b24a7adb89b
Patch-mainline: v5.10-rc2
References: bsc#1164648
UBSAN reports:
Undefined behaviour in ./include/linux/time64.h:127:27
signed integer overflow:
17179869187 * 1000000000 cannot be represented in type 'long long int'
Call Trace:
timespec64_to_ns include/linux/time64.h:127 [inline]
set_cpu_itimer+0x65c/0x880 kernel/time/itimer.c:180
do_setitimer+0x8e/0x740 kernel/time/itimer.c:245
__x64_sys_setitimer+0x14c/0x2c0 kernel/time/itimer.c:336
do_syscall_64+0xa1/0x540 arch/x86/entry/common.c:295
Commit bd40a175769d ("y2038: itimer: change implementation to timespec64")
replaced the original conversion which handled time clamping correctly with
timespec64_to_ns() which has no overflow protection.
Fix it in timespec64_to_ns() as this is not necessarily limited to the
usage in itimers.
[ tglx: Added comment and adjusted the fixes tag ]
Fixes: 361a3bf00582 ("time64: Add time64.h header and define struct timespec64")
Signed-off-by: Zeng Tao <prime.zeng@hisilicon.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/1598952616-6416-1-git-send-email-prime.zeng@hisilicon.com
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
---
include/linux/time64.h | 4 ++++
kernel/time/itimer.c | 4 ----
2 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/include/linux/time64.h b/include/linux/time64.h
index a620ee610b9f..1ffba1de8029 100644
--- a/include/linux/time64.h
+++ b/include/linux/time64.h
@@ -130,6 +130,10 @@ static inline bool timespec64_valid_settod(const struct timespec64 *ts)
*/
static inline s64 timespec64_to_ns(const struct timespec64 *ts)
{
+ /* Prevent multiplication overflow */
+ if ((unsigned long long)ts->tv_sec >= KTIME_SEC_MAX)
+ return KTIME_MAX;
+
return ((s64) ts->tv_sec * NSEC_PER_SEC) + ts->tv_nsec;
}
diff --git a/kernel/time/itimer.c b/kernel/time/itimer.c
index 02068b2d5862..1932450a7f35 100644
--- a/kernel/time/itimer.c
+++ b/kernel/time/itimer.c
@@ -152,10 +152,6 @@ static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
u64 oval, nval, ointerval, ninterval;
struct cpu_itimer *it = &tsk->signal->it[clock_id];
- /*
- * Use the to_ktime conversion because that clamps the maximum
- * value to KTIME_MAX and avoid multiplication overflows.
- */
nval = ktime_to_ns(timeval_to_ktime(value->it_value));
ninterval = ktime_to_ns(timeval_to_ktime(value->it_interval));
--
2.26.2