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Commit 68e51bf3 authored by Zeng Tao's avatar Zeng Tao Committed by Greg Kroah-Hartman
Browse files

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: 361a3bf0 ("time64: Add time64.h header and define struct timespec64")
Signed-off-by: default avatarZeng Tao <prime.zeng@hisilicon.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarArnd 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: default avatarSasha Levin <sashal@kernel.org>
parent 7d222dce

include/linux/time64.h

+4 −0
Original line number Diff line number Diff line
@@ -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;

}

kernel/time/itimer.c

+0 −4
Original line number Diff line number Diff line
@@ -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));