linux-kernel - [tip:timers/core] time: Prevent 32 bit overflow with set_normalized

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-ID: <tip-12e09337fe238981cb0c87543306e23775d1a143@git.kernel.org>
Date:	Tue, 15 Sep 2009 08:22:02 GMT
From:	tip-bot for Thomas Gleixner <tglx@...utronix.de>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	johnstul@...ibm.com, schwidefsky@...ibm.com, tglx@...utronix.de,
	carsten.emde@...dl.org
Subject: [tip:timers/core] time: Prevent 32 bit overflow with set_normalized_timespec()

Commit-ID:  12e09337fe238981cb0c87543306e23775d1a143
Gitweb:     http://git.kernel.org/tip/12e09337fe238981cb0c87543306e23775d1a143
Author:     Thomas Gleixner <tglx@...utronix.de>
AuthorDate: Mon, 14 Sep 2009 23:37:40 +0200
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Tue, 15 Sep 2009 10:17:30 +0200

time: Prevent 32 bit overflow with set_normalized_timespec()

set_normalized_timespec() nsec argument is of type long. The recent
timekeeping changes of ktime_get_ts() feed 

	ts->tv_nsec + tomono.tv_nsec + nsecs

to set_normalized_timespec(). On 32 bit machines that sum can be
larger than (1 << 31) and therefor result in a negative value which
screws up the result completely.

Make the nsec argument of set_normalized_timespec() s64 to fix the
problem at hand. This also prevents similar problems for future users
of set_normalized_timespec().

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Tested-by: Carsten Emde <carsten.emde@...dl.org>
LKML-Reference: <new-submission>
Cc: Martin Schwidefsky <schwidefsky@...ibm.com>
Cc: John Stultz <johnstul@...ibm.com>



---
 include/linux/time.h |    2 +-
 kernel/time.c        |    9 ++++++++-
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/include/linux/time.h b/include/linux/time.h
index 256232f..56787c0 100644
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -75,7 +75,7 @@ extern unsigned long mktime(const unsigned int year, const unsigned int mon,
 			    const unsigned int day, const unsigned int hour,
 			    const unsigned int min, const unsigned int sec);
 
-extern void set_normalized_timespec(struct timespec *ts, time_t sec, long nsec);
+extern void set_normalized_timespec(struct timespec *ts, time_t sec, s64 nsec);
 extern struct timespec timespec_add_safe(const struct timespec lhs,
 					 const struct timespec rhs);
 
diff --git a/kernel/time.c b/kernel/time.c
index 2951194..2e2e469 100644
--- a/kernel/time.c
+++ b/kernel/time.c
@@ -370,13 +370,20 @@ EXPORT_SYMBOL(mktime);
  *	0 <= tv_nsec < NSEC_PER_SEC
  * For negative values only the tv_sec field is negative !
  */
-void set_normalized_timespec(struct timespec *ts, time_t sec, long nsec)
+void set_normalized_timespec(struct timespec *ts, time_t sec, s64 nsec)
 {
 	while (nsec >= NSEC_PER_SEC) {
+		/*
+		 * The following asm() prevents the compiler from
+		 * optimising this loop into a modulo operation. See
+		 * also __iter_div_u64_rem() in include/linux/time.h
+		 */
+		asm("" : "+rm"(nsec));
 		nsec -= NSEC_PER_SEC;
 		++sec;
 	}
 	while (nsec < 0) {
+		asm("" : "+rm"(nsec));
 		nsec += NSEC_PER_SEC;
 		--sec;
 	}
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/