| 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: time: Prevent undefined behaviour in timespec64_to_ns() |
| |
| From: Zeng Tao <prime.zeng@hisilicon.com> |
| |
| commit cb47755725da7b90fecbb2aa82ac3b24a7adb89b upstream. |
| |
| 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: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| include/linux/time64.h | 4 ++++ |
| kernel/time/itimer.c | 4 ---- |
| 2 files changed, 4 insertions(+), 4 deletions(-) |
| |
| --- a/include/linux/time64.h |
| +++ b/include/linux/time64.h |
| @@ -124,6 +124,10 @@ static inline bool timespec64_valid_sett |
| */ |
| 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; |
| } |
| |
| --- a/kernel/time/itimer.c |
| +++ b/kernel/time/itimer.c |
| @@ -172,10 +172,6 @@ static void set_cpu_itimer(struct task_s |
| 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); |
| |