On Thu, Apr 19, 2018 at 05:15:20PM -0700, Andrew Morton wrote:
> On Wed, 21 Feb 2018 22:30:09 +0300 Alexey Dobriyan <[email protected]>
> wrote:
>
> > "rv" variable is used both as a counter of bytes transferred and
> > an error value holder but it can be reduced solely to error values
> > if original start of userspace buffer is stashed and used at the very
> > end.
> >
> > ...
> >
> > --- a/fs/proc/base.c
> > +++ b/fs/proc/base.c
> >
> > ...
> >
> > @@ -371,12 +365,16 @@ static ssize_t proc_pid_cmdline_read(struct file
> > *file, char __user *buf,
> > }
> > }
> >
> > +end:
> > + free_page((unsigned long)page);
> > + mmput(mm);
> > + *pos += buf - buf0;
> > + return buf - buf0;
> > +
> > out_free_page:
> > free_page((unsigned long)page);
> > out_mmput:
> > mmput(mm);
> > - if (rv > 0)
> > - *pos += rv;
> > return rv;
> > }
>
> (scratches head). Why not do this?
>
> --- a/fs/proc/base.c~proc-simpler-iterations-for-proc-cmdline-fix
> +++ a/fs/proc/base.c
> @@ -363,11 +363,8 @@ static ssize_t proc_pid_cmdline_read(str
> }
>
> end:
> - free_page((unsigned long)page);
> - mmput(mm);
> *pos += buf - buf0;
> - return buf - buf0;
> -
> + rv = buf - buf0;
> out_free_page:
> free_page((unsigned long)page);
> out_mmput:
>
> (and maybe rv should be ssize_t)
It should as cmdline area can be set to arbitrary values.
I hate ssize_t and it's bloat.
$ ./scripts/bloat-o-meter ../vmlinux-000 ../obj/vmlinux
add/remove: 0/0 grow/shrink: 1/0 up/down: 11/0 (11)
Function old new delta
proc_pid_cmdline_read 867 878 +11
