linux-kernel - [PATCH 3.16.y-ckt 076/129] cputime: Prevent 32bit overflow in time[val|spec]_to

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Message-Id: <1456482100-4667-77-git-send-email-luis.henriques@canonical.com>
Date:	Fri, 26 Feb 2016 10:20:47 +0000
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	zengtao <prime.zeng@...wei.com>, <fweisbec@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 076/129] cputime: Prevent 32bit overflow in time[val|spec]_to_cputime()

3.16.7-ckt25 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: zengtao <prime.zeng@...wei.com>

commit 0f26922fe5dc5724b1adbbd54b21bad03590b4f3 upstream.

The datatype __kernel_time_t is u32 on 32bit platform, so its subject to
overflows in the timeval/timespec to cputime conversion.

Currently the following functions are affected:
1. setitimer()
2. timer_create/timer_settime()
3. sys_clock_nanosleep

This can happen on MIPS32 and ARM32 with "Full dynticks CPU time accounting"
enabled, which is required for CONFIG_NO_HZ_FULL.

Enforce u64 conversion to prevent the overflow.

Fixes: 31c1fc818715 ("ARM: Kconfig: allow full nohz CPU accounting")
Signed-off-by: zengtao <prime.zeng@...wei.com>
Reviewed-by: Arnd Bergmann <arnd@...db.de>
Cc: <fweisbec@...il.com>
Link: http://lkml.kernel.org/r/1454384314-154784-1-git-send-email-prime.zeng@huawei.com
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 include/asm-generic/cputime_nsecs.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/include/asm-generic/cputime_nsecs.h b/include/asm-generic/cputime_nsecs.h
index 4e817606c549..564ecc9061bc 100644
--- a/include/asm-generic/cputime_nsecs.h
+++ b/include/asm-generic/cputime_nsecs.h
@@ -73,7 +73,7 @@ typedef u64 __nocast cputime64_t;
  */
 static inline cputime_t timespec_to_cputime(const struct timespec *val)
 {
-	u64 ret = val->tv_sec * NSEC_PER_SEC + val->tv_nsec;
+	u64 ret = (u64)val->tv_sec * NSEC_PER_SEC + val->tv_nsec;
 	return (__force cputime_t) ret;
 }
 static inline void cputime_to_timespec(const cputime_t ct, struct timespec *val)
@@ -89,7 +89,8 @@ static inline void cputime_to_timespec(const cputime_t ct, struct timespec *val)
  */
 static inline cputime_t timeval_to_cputime(const struct timeval *val)
 {
-	u64 ret = val->tv_sec * NSEC_PER_SEC + val->tv_usec * NSEC_PER_USEC;
+	u64 ret = (u64)val->tv_sec * NSEC_PER_SEC +
+			val->tv_usec * NSEC_PER_USEC;
 	return (__force cputime_t) ret;
 }
 static inline void cputime_to_timeval(const cputime_t ct, struct timeval *val)