From 979515c5645830465739254abc1b1648ada41518 Mon Sep 17 00:00:00 2001 From: Vegard Nossum Date: Sat, 13 Aug 2016 01:37:04 +0200 Subject: time: Avoid undefined behaviour in ktime_add_safe() I ran into this: ================================================================================ UBSAN: Undefined behaviour in kernel/time/hrtimer.c:310:16 signed integer overflow: 9223372036854775807 + 50000 cannot be represented in type 'long long int' CPU: 2 PID: 4798 Comm: trinity-c2 Not tainted 4.8.0-rc1+ #91 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.9.3-0-ge2fc41e-prebuilt.qemu-project.org 04/01/2014 0000000000000000 ffff88010ce6fb88 ffffffff82344740 0000000041b58ab3 ffffffff84f97a20 ffffffff82344694 ffff88010ce6fbb0 ffff88010ce6fb60 000000000000c350 ffff88010ce6f968 dffffc0000000000 ffffffff857bc320 Call Trace: [] dump_stack+0xac/0xfc [] ? _atomic_dec_and_lock+0xc4/0xc4 [] ubsan_epilogue+0xd/0x8a [] handle_overflow+0x202/0x23d [] ? val_to_string.constprop.6+0x11e/0x11e [] ? timerqueue_add+0x151/0x410 [] ? hrtimer_start_range_ns+0x3b8/0x1380 [] ? memset+0x31/0x40 [] __ubsan_handle_add_overflow+0xe/0x10 [] hrtimer_nanosleep+0x5d9/0x790 [] ? hrtimer_init_sleeper+0x80/0x80 [] ? __might_sleep+0x5b/0x260 [] common_nsleep+0x20/0x30 [] SyS_clock_nanosleep+0x197/0x210 [] ? SyS_clock_getres+0x150/0x150 [] ? __this_cpu_preempt_check+0x13/0x20 [] ? __context_tracking_exit.part.3+0x30/0x1b0 [] ? SyS_clock_getres+0x150/0x150 [] do_syscall_64+0x1b3/0x4b0 [] entry_SYSCALL64_slow_path+0x25/0x25 ================================================================================ Add a new ktime_add_unsafe() helper which doesn't check for overflow, but doesn't throw a UBSAN warning when it does overflow either. Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Richard Cochran Cc: Prarit Bhargava Signed-off-by: Vegard Nossum Signed-off-by: John Stultz --- kernel/time/hrtimer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel') diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c index 252ea4741592..bb5ec425dfe0 100644 --- a/kernel/time/hrtimer.c +++ b/kernel/time/hrtimer.c @@ -307,7 +307,7 @@ EXPORT_SYMBOL_GPL(__ktime_divns); */ ktime_t ktime_add_safe(const ktime_t lhs, const ktime_t rhs) { - ktime_t res = ktime_add(lhs, rhs); + ktime_t res = ktime_add_unsafe(lhs, rhs); /* * We use KTIME_SEC_MAX here, the maximum timeout which we can -- cgit v1.2.3