On 03/26/2013 10:21:04 PM, Wang Dongsheng-B40534 wrote:
> -----Original Message-----
> From: Wood Scott-B07421
> Sent: Wednesday, March 27, 2013 1:36 AM
> To: Wang Dongsheng-B40534
> Cc: Wood Scott-B07421; Gala Kumar-B11780;
linuxppc-dev@lists.ozlabs.org;
> Zhao Chenhui-B35336; Li Yang-R58472
> Subject: Re: [PATCH 3/3] powerpc/fsl: add MPIC timer wakeup support
>
> On 03/25/2013 10:27:24 PM, Wang Dongsheng-B40534 wrote:
> >
> >
> > > -----Original Message-----
> > > From: Wood Scott-B07421
> > > Sent: Saturday, March 23, 2013 6:11 AM
> > > To: Wang Dongsheng-B40534
> > > Cc: Wood Scott-B07421; Gala Kumar-B11780;
> > linuxppc-dev@lists.ozlabs.org;
> > > Zhao Chenhui-B35336; Li Yang-R58472
> > > Subject: Re: [PATCH 3/3] powerpc/fsl: add MPIC timer wakeup
support
> > >
> > > On 03/22/2013 12:46:24 AM, Wang Dongsheng-B40534 wrote:
> > > > Under what case is unsafe, please make sense.
> > >
> > > char buffer[1] = { '5' };
> > > write(fd, &buffer, 1);
> > >
> > > What comes after that '5' byte in the pointer you pass to
kstrtol?
> > >
> > The buffer is userspace. It will fall in the kernel space.
> > Kernel will get a free page, and copy the buffer to page.
> > This page has been cleared before copy to page.
> > The page has already have null-terminated.
>
> It doesn't allocate a whole page, it uses kmalloc (not kzalloc!).
Even
> if kzalloc were used, a larger user buffer could be the exact size
of the
> region that was allocated.
>
> See memdup_user() in mm/util.c
>
Did you miss something?
See fill_write_buffer() in fs/sysfs/file.c. It's used
get_zeroed_page()...
OK, I was looking at fs/sysfs/bin.c which is something slightly
different.
fill_write_buffer() forces the size to be no more than "PAGE_SIZE - 1"
so we know there's a terminator.
Perhaps kernel/rtmutex-tester.c and kernel/time/clocksource.c are
similarly confused?
-Scott
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