From 2a3c581973756b8f08df4749de848d86bd46665d Mon Sep 17 00:00:00 2001 From: Xiongfeng Wang Date: Fri, 8 Mar 2019 15:00:56 +0800 Subject: [PATCH] posix-cpu-timers: Avoid undefined behaviour in timespec64_to_ns() euler inclusion category: feature Bugzilla: 10876 CVE: N/A ---------------------------------------- When I ran Syzkaller testsuite, I got the following call trace. Reviewed-by: Yang Yingliang ================================================================================ UBSAN: Undefined behaviour in ./include/linux/time64.h:120:27 signed integer overflow: 8243129037239968815 * 1000000000 cannot be represented in type 'long long int' CPU: 5 PID: 28854 Comm: syz-executor.1 Not tainted 4.19.24 #4 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.11.0-0-g63451fca13-prebuilt.qemu-project.org 04/01/2014 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0xca/0x13e lib/dump_stack.c:113 ubsan_epilogue+0xe/0x81 lib/ubsan.c:159 handle_overflow+0x193/0x1e2 lib/ubsan.c:190 timespec64_to_ns include/linux/time64.h:120 [inline] posix_cpu_timer_set+0x95a/0xb70 kernel/time/posix-cpu-timers.c:687 do_timer_settime+0x198/0x2a0 kernel/time/posix-timers.c:892 __do_sys_timer_settime kernel/time/posix-timers.c:918 [inline] __se_sys_timer_settime kernel/time/posix-timers.c:904 [inline] __x64_sys_timer_settime+0x18d/0x260 kernel/time/posix-timers.c:904 do_syscall_64+0xc8/0x580 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x462eb9 Code: f7 d8 64 89 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f14e4127c58 EFLAGS: 00000246 ORIG_RAX: 00000000000000df RAX: ffffffffffffffda RBX: 000000000073bfa0 RCX: 0000000000462eb9 RDX: 0000000020000080 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 0000000000000004 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f14e41286bc R13: 00000000004c54cc R14: 0000000000704278 R15: 00000000ffffffff ================================================================================ It is because 'it_interval.tv_sec' is larger than 'KTIME_SEC_MAX' and 'it_interval.tv_sec * NSEC_PER_SEC' overflows in 'timespec64_to_ns()'. This patch checks whether 'it_interval.tv_sec' is larger than 'KTIME_SEC_MAX' and saturate if that is the case. Signed-off-by: Xiongfeng Wang Reviewed-by: Yang Yingliang Signed-off-by: Yang Yingliang --- kernel/time/posix-timers.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c index 5a01c4fdbfef..977bb6b78b0c 100644 --- a/kernel/time/posix-timers.c +++ b/kernel/time/posix-timers.c @@ -877,6 +877,14 @@ static int do_timer_settime(timer_t timer_id, int flags, if (!timespec64_valid(&new_spec64->it_interval) || !timespec64_valid(&new_spec64->it_value)) return -EINVAL; + if (new_spec64->it_interval.tv_sec >= KTIME_SEC_MAX) { + new_spec64->it_interval.tv_sec = KTIME_SEC_MAX; + new_spec64->it_interval.tv_nsec = 0; + } + if (new_spec64->it_value.tv_sec >= KTIME_SEC_MAX) { + new_spec64->it_value.tv_sec = KTIME_SEC_MAX; + new_spec64->it_value.tv_nsec = 0; + } if (old_spec64) memset(old_spec64, 0, sizeof(*old_spec64)); -- GitLab