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

Commit-ID: cb47755725da7b90fecbb2aa82ac3b24a7adb89b Gitweb: https://git.kernel.org/tip/cb47755725da7b90fecbb2aa82ac3b24a7adb89b Author: Zeng Tao prime.zeng@hisilicon.com AuthorDate: Tue, 01 Sep 2020 17:30:13 +08:00 Committer: Thomas Gleixner tglx@linutronix.de CommitterDate: Mon, 26 Oct 2020 11:48:11 +01:00

time: Prevent undefined behaviour in timespec64_to_ns()

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@hisili... --- 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 c9dcb3e..5117cb5 100644 --- a/include/linux/time64.h +++ b/include/linux/time64.h @@ -124,6 +124,10 @@ 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 ca4e6d5..00629e6 100644 --- a/kernel/time/itimer.c +++ b/kernel/time/itimer.c @@ -172,10 +172,6 @@ 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 = timespec64_to_ns(&value->it_value); ninterval = timespec64_to_ns(&value->it_interval);