2022-08-18 12:25:33

by Vincent Whitchurch

Subject: [PATCH v2] tty: Fix lookahead_buf crash with serdev

Do not follow a NULL pointer if the tty_port_client_operations does not
implement the ->lookahead_buf() callback, which is the case with
serdev's ttyport.

Fixes: 6bb6fa6908ebd3 ("tty: Implement lookahead to process XON/XOFF timely")
Signed-off-by: Vincent Whitchurch <[email protected]>
---

Notes:
v2: Move more stuff into if block.

drivers/tty/tty_buffer.c | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c
index 9fdecc795b6b..5e287dedce01 100644
--- a/drivers/tty/tty_buffer.c
+++ b/drivers/tty/tty_buffer.c
@@ -470,7 +470,6 @@ static void lookahead_bufs(struct tty_port *port, struct tty_buffer *head)

while (head) {
struct tty_buffer *next;
- unsigned char *p, *f = NULL;
unsigned int count;

/*
@@ -489,11 +488,16 @@ static void lookahead_bufs(struct tty_port *port, struct tty_buffer *head)
continue;
}

- p = char_buf_ptr(head, head->lookahead);
- if (~head->flags & TTYB_NORMAL)
- f = flag_buf_ptr(head, head->lookahead);
+ if (port->client_ops->lookahead_buf) {
+ unsigned char *p, *f = NULL;
+
+ p = char_buf_ptr(head, head->lookahead);
+ if (~head->flags & TTYB_NORMAL)
+ f = flag_buf_ptr(head, head->lookahead);
+
+ port->client_ops->lookahead_buf(port, p, f, count);
+ }

- port->client_ops->lookahead_buf(port, p, f, count);
head->lookahead += count;
}
}
--
2.34.1

2022-08-18 12:42:21

by Ilpo Järvinen

Subject: Re: [PATCH v2] tty: Fix lookahead_buf crash with serdev

On Thu, 18 Aug 2022, Vincent Whitchurch wrote:

> Do not follow a NULL pointer if the tty_port_client_operations does not
> implement the ->lookahead_buf() callback, which is the case with
> serdev's ttyport.
>
> Fixes: 6bb6fa6908ebd3 ("tty: Implement lookahead to process XON/XOFF timely")
> Signed-off-by: Vincent Whitchurch <[email protected]>

Reviewed-by: Ilpo J?rvinen <[email protected]>

--
i.

> ---
>
> Notes:
> v2: Move more stuff into if block.
>
> drivers/tty/tty_buffer.c | 14 +++++++++-----
> 1 file changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c
> index 9fdecc795b6b..5e287dedce01 100644
> --- a/drivers/tty/tty_buffer.c
> +++ b/drivers/tty/tty_buffer.c
> @@ -470,7 +470,6 @@ static void lookahead_bufs(struct tty_port *port, struct tty_buffer *head)
>
> while (head) {
> struct tty_buffer *next;
> - unsigned char *p, *f = NULL;
> unsigned int count;
>
> /*
> @@ -489,11 +488,16 @@ static void lookahead_bufs(struct tty_port *port, struct tty_buffer *head)
> continue;
> }
>
> - p = char_buf_ptr(head, head->lookahead);
> - if (~head->flags & TTYB_NORMAL)
> - f = flag_buf_ptr(head, head->lookahead);
> + if (port->client_ops->lookahead_buf) {
> + unsigned char *p, *f = NULL;
> +
> + p = char_buf_ptr(head, head->lookahead);
> + if (~head->flags & TTYB_NORMAL)
> + f = flag_buf_ptr(head, head->lookahead);
> +
> + port->client_ops->lookahead_buf(port, p, f, count);
> + }
>
> - port->client_ops->lookahead_buf(port, p, f, count);
> head->lookahead += count;
> }
> }
>