2022-03-28 14:52:32

by Sven Schnelle

[permalink] [raw]
Subject: Re: [PATCH v2] char: tty3270: fix a missing check on list iterator

Xiaomeng Tong <[email protected]> writes:

> --- a/drivers/s390/char/tty3270.c
> +++ b/drivers/s390/char/tty3270.c
> @@ -1111,7 +1111,7 @@ tty3270_convert_line(struct tty3270 *tp, int line_nr)
> {
> struct tty3270_line *line;
> struct tty3270_cell *cell;
> - struct string *s, *n;
> + struct string *s = NULL, *n, *iter;

Please keep reverse XMAS-tree layout.

> unsigned char highlight;
> unsigned char f_color;
> char *cp;
> @@ -1142,13 +1142,20 @@ tty3270_convert_line(struct tty3270 *tp, int line_nr)
>
> /* Find the line in the list. */
> i = tp->view.rows - 2 - line_nr;
> - list_for_each_entry_reverse(s, &tp->lines, list)
> - if (--i <= 0)
> + list_for_each_entry_reverse(iter, &tp->lines, list)
> + if (--i <= 0) {
> + s = iter;
> break;
> + }
> /*
> * Check if the line needs to get reallocated.
> */
> - if (s->len != flen) {
> + if (!s) {
> + /* Reallocate string. */
> + n = tty3270_alloc_string(tp, flen);
> + list_add(&n->list, &tp->lines);
> + s = n;
> + } else if (s->len != flen) {
> /* Reallocate string. */
> n = tty3270_alloc_string(tp, flen);
> list_add(&n->list, &s->list);

I should have written that in my first reply, but s == NULL means
the given line number couldn't be found in the list of lines. This is
a serious error and should be warned about. So maybe something like:

if (WARN_ON(!s))
return;

But allocating a new empty line in that case is certainly wrong.

Thanks
Sven


2022-03-28 20:28:08

by Xiaomeng Tong

[permalink] [raw]
Subject: Re: [PATCH v2] char: tty3270: fix a missing check on list iterator

> I should have written that in my first reply, but s == NULL means
> the given line number couldn't be found in the list of lines. This is
> a serious error and should be warned about. So maybe something like:
>
> if (WARN_ON(!s))
> return;
>
> But allocating a new empty line in that case is certainly wrong.

Thank you, i have resend a v3 patch as you suggested.

--
Xiaomeng Tong