From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Fri, 17 Jun 2016 11:36:48 -0400 From: Steven Rostedt To: Jens Axboe Cc: Arnd Bergmann , Ingo Molnar , y2038@lists.linaro.org, Hannes Reinecke , Mike Christie , Shaohua Li , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] blktrace: avoid using timespec Message-ID: <20160617113648.69448c9f@gandalf.local.home> In-Reply-To: <20160617145849.3771756-1-arnd@arndb.de> References: <20160617145849.3771756-1-arnd@arndb.de> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII List-ID: Jens, You want to take this, or do you want me to? -- Steve On Fri, 17 Jun 2016 16:58:26 +0200 Arnd Bergmann wrote: > The blktrace code stores the current time in a 32-bit word in its > user interface. This is a bad idea because 32-bit seconds overflow > at some point. > > We probably have until 2106 before this one overflows, as it seems > to use an 'unsigned' variable, but we should confirm that user > space treats it the same way. > > Aside from this, we want to stop using 'struct timespec' here, > so I'm adding a comment about the overflow and change the code > to use timespec64 instead to make the loss of range more obvious. > > Signed-off-by: Arnd Bergmann > --- > kernel/trace/blktrace.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c > index ef86b965ade3..b0816e4a61a5 100644 > --- a/kernel/trace/blktrace.c > +++ b/kernel/trace/blktrace.c > @@ -127,12 +127,13 @@ static void trace_note_tsk(struct task_struct *tsk) > > static void trace_note_time(struct blk_trace *bt) > { > - struct timespec now; > + struct timespec64 now; > unsigned long flags; > u32 words[2]; > > - getnstimeofday(&now); > - words[0] = now.tv_sec; > + /* need to check user space to see if this breaks in y2038 or y2106 */ > + ktime_get_real_ts64(&now); > + words[0] = (u32)now.tv_sec; > words[1] = now.tv_nsec; > > local_irq_save(flags);