Re: [PATCH][v2] proc: use vmalloc for our kernel buffer

[Josef Bacik]

On 8/13/20 1:31 PM, Al Viro wrote:
> On Thu, Aug 13, 2020 at 01:19:18PM -0400, Josef Bacik wrote:
>
> > > in sunrpc proc_dodebug() turns into
> > > 		left -= snprintf(buffer, left, "0x%04x\n",
> 					 ^^^^
> 					 left + 1, that is.
>
> > > 				 *(unsigned int *) table->data);
> > > and that's not the only example.
> >
> > We wouldn't even need the extra +1 part, since we're only copying in how
> > much the user wants anyway, we could just go ahead and convert this to
> >
> > left -= snprintf(buffer, left, "0x%04x\n", *(unsigned int *) table->data);
> >
> > and be fine, right?  Or am I misunderstanding what you're looking for?  Thanks,
>
> snprintf() always produces a NUL-terminated string.  And if you are passing 7 as
> len, you want 0xf0ad\n to be copied to user.  For that you need 8 passed to
> snprintf, and 8-byte buffer given to it.

Right, gotcha.  I'll rig that up and see how it looks.  I'd recommend looking 
through what I do with a fine tooth comb, I'm obviously not batting 1000 today. 
Thanks,

Josef