lkml.org 
[lkml]   [2015]   [Dec]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [RESEND v4 2/6] remoteproc: debugfs: Add ability to boot remote processor using debugfs
Date
On Thursday 03 December 2015 13:03:41 Lee Jones wrote:
> On Thu, 03 Dec 2015, Arnd Bergmann wrote:
>
> > On Thursday 03 December 2015 12:26:34 Lee Jones wrote:
> > > > >
> > > > > +static ssize_t rproc_state_write(struct file *filp, const char __user *userbuf,
> > > > > + size_t count, loff_t *ppos)
> > > > > +{
> > > > > + struct rproc *rproc = filp->private_data;
> > > > > + char buf[10];
> > > > > + int ret;
> > > > > +
> > > > > + if (count > sizeof(buf))
> > > > > + return count;
> > > > > + ret = copy_from_user(buf, userbuf, count);
> > > > > + if (ret)
> > > > > + return -EFAULT;
> > > > > +
> > > > > + if (buf[count - 1] == '\n')
> > > > > + buf[count - 1] = '\0';
> > > >
> > > > I believe you can get here with count = 0.
> > >
> > > I'm pretty sure you can't.
> > >
> > > If you are sure that you can, if you can provide me with a way of
> > > testing, I'd be happy to put in provisions.
> > >
> >
> > I think that a zero-length write() from user space ends up in the write
> > file operation.
>
> I tested this and didn't see it enter write(). My conclusion was that
> if the file doesn't change, then nothing is triggered.
>

Ah, interesting. I haven't tried myself, and just tried to read the
code. Maybe glibc already catches zero-length writes before it gets
into the kernel, or I just missed the part of the syscall that checks
for this.

arnd


\
 
 \ /
  Last update: 2015-12-03 14:41    [W:0.077 / U:0.252 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site