This is a note to let you know that I've just added the patch titled time: Prevent undefined behaviour in timespec64_to_ns() to the 4.19-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: time-prevent-undefined-behaviour-in-timespec64_to_ns.patch and it can be found in the queue-4.19 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit c5021b2547ad5b6ca573c6675d78c0930f32eb9e Author: Zeng Tao <prime.zeng@xxxxxxxxxxxxx> Date: Tue Sep 1 17:30:13 2020 +0800 time: Prevent undefined behaviour in timespec64_to_ns() [ Upstream commit cb47755725da7b90fecbb2aa82ac3b24a7adb89b ] 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@xxxxxxxxxxxxx> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Reviewed-by: Arnd Bergmann <arnd@xxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Link: https://lore.kernel.org/r/1598952616-6416-1-git-send-email-prime.zeng@xxxxxxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/include/linux/time64.h b/include/linux/time64.h index 4a45aea0f96e9..8dbdf6cae3e8b 100644 --- a/include/linux/time64.h +++ b/include/linux/time64.h @@ -138,6 +138,10 @@ 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 9a65713c83093..2e2b335ef1018 100644 --- a/kernel/time/itimer.c +++ b/kernel/time/itimer.c @@ -154,10 +154,6 @@ 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));