[PATCH 3/3] powerpc/fsl: add MPIC timer wakeup support

[Wang Dongsheng-B40534]

> -----Original Message-----
> From: Wood Scott-B07421
> Sent: Thursday, March 28, 2013 4:26 AM
> To: Wang Dongsheng-B40534
> Cc: Wood Scott-B07421; Gala Kumar-B11780; linuxppc-dev at lists.ozlabs.org;
> Zhao Chenhui-B35336; Li Yang-R58472
> Subject: Re: [PATCH 3/3] powerpc/fsl: add MPIC timer wakeup support
> 
> 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 at 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 at 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?
> 
Yes. But its depends on file->f_op.
See vfs_write in fs/read_write.c.