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)
