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SubjectRe: [PATCH] 2.5.31-serport
On Fri, Aug 30, 2002 at 10:39:11PM +0100, Russell King wrote:
> This patch appears not to be in 2.5.32, but applies cleanly.
>
> serport/serio presently has several problems. This is by no means a
> definitive list (for example, the locking problems that hch reported
> back in 2.4.0-test time):
>
> 1. Insomnia. When someone closes the serport device, it wakes up a
> thread in serport_ldisc_read(). Unfortunately, if serport->serio.type
> is non-zero and we haven't received a signal, we re-call schedule()
> without changing current->state. So schedule returns, and repeat
> for ever.
>
> A better sleep solution would be:
>
> wait_event_interruptible((&serport->wait, serport->serio.type);
>
> which contains all the knoweldge of handling sleeping.
>
> Someone might also think about what serport_serio_close() is actually
> trying to do. If its intended to cause the thread in ldisc_read exit,
> it should set serport->serio.type to 0.

I'll answer to this as soon as I get some sleep. No pun originally
intended.

> 2. What happens if I open and try to read from this port while something
> has the serport_ldisc attached? I suspect that you'll create nice
> loop of serio devices in serio.c and an infinite loop when you try to
> traverse the list to remove a different serio device.

Just to make sure - the scenario would be: inputattach opening
/dev/ttyS0, setting N_MOUSE ldisc. Mouse driver opening that serio, etc,
etc. Then I run minicom on /dev/ttyS0?

> 3. Naming:
>
> #ifdef CONFIG_DEVFS_FS
> sprintf(name, tty->driver.name, minor(tty->device) - tty->driver.minor_start);
> #else
> sprintf(name, "%s%d", tty->driver.name, minor(tty->device) - tty->driver.minor_start);
> #endif
>
> should probably be using tty_name(), rather than trying to construct
> the name itself.

Definitely. Not sure if that existed at the time this was written.
Probably yes, though.

> 4. Stack overflows. There seems to be confusion about how long a tty name
> can be, and we seem to add characters to the name ("/serio0") and then
> squash it into a smaller buffer.
>
> char ttyname[64];
> ...
> strcpy(ttyname, tty->driver.name);
> ...
> sprintf(serport->phys, "%s%d/serio0", ttyname, minor(tty->device) - tty$
> However, serport->phys is declared as:
>
> struct serport {
> char phys[32];
> };
>
> I'd suggest using strncpy() and snprintf() here, and adjusting the size of
> those strings so they're sensible.

Indeed.

> This patch fixes (1) and (3) completey. (4) needs the sizes reviewed and fixed.
> (2) is NOT fixed by this patch.
>
> drivers/input/serio/serio.c | 8 ++++++++
> drivers/input/serio/serport.c | 26 ++++++++------------------
> 2 files changed, 16 insertions, 18 deletions
>
> diff -ur orig/drivers/input/serio/serio.c linux/drivers/input/serio/serio.c
> --- orig/drivers/input/serio/serio.c Fri Aug 2 21:13:28 2002
> +++ linux/drivers/input/serio/serio.c Sun Aug 11 16:15:00 2002
> @@ -122,6 +122,8 @@
>
> void serio_register_port(struct serio *serio)
> {
> + BUG_ON(serio->next);
> +
> serio->next = serio_list;
> serio_list = serio;
> serio_find_dev(serio);
> @@ -134,6 +136,8 @@
> while (*serioptr && (*serioptr != serio)) serioptr = &((*serioptr)->next);
> *serioptr = (*serioptr)->next;
>
> + serio->next = NULL;
> +
> if (serio->dev && serio->dev->disconnect)
> serio->dev->disconnect(serio);
> }
> @@ -142,6 +146,8 @@
> {
> struct serio *serio = serio_list;
>
> + BUG_ON(dev->next);
> +
> dev->next = serio_dev;
> serio_dev = dev;
>
> @@ -159,6 +165,8 @@
>
> while (*devptr && (*devptr != dev)) devptr = &((*devptr)->next);
> *devptr = (*devptr)->next;
> +
> + dev->next = NULL;
>
> while (serio) {
> if (serio->dev == dev && dev->disconnect)

This should better be fixed by switching to <linux/list.h> for the
linked lists.

> diff -ur orig/drivers/input/serio/serport.c linux/drivers/input/serio/serport.c
> --- orig/drivers/input/serio/serport.c Sat Jul 27 13:55:18 2002
> +++ linux/drivers/input/serio/serport.c Sun Aug 11 16:33:59 2002
> @@ -96,11 +96,14 @@
> serport->tty = tty;
> tty->disc_data = serport;
>
> - strcpy(ttyname, tty->driver.name);
> - for (i = 0; ttyname[i] != 0 && ttyname[i] != '/'; i++);
> + strncpy(ttyname, tty->driver.name, sizeof(ttyname) - 1);
> +
> + for (i = 0; ttyname[i] != 0 && ttyname[i] != '/' &&
> + i < sizeof(ttyname) - 1; i++);
> ttyname[i] = 0;
>
> - sprintf(serport->phys, "%s%d/serio0", ttyname, minor(tty->device) - tty->driver.minor_start);
> + snprintf(serport->phys, sizeof(serport->phys), "%s%d/serio0",
> + ttyname, minor(tty->device) - tty->driver.minor_start);
>
> serport->serio.name = serport_name;
> serport->serio.phys = serport->phys;
> @@ -161,26 +164,13 @@
> static ssize_t serport_ldisc_read(struct tty_struct * tty, struct file * file, unsigned char * buf, size_t nr)
> {
> struct serport *serport = (struct serport*) tty->disc_data;
> - DECLARE_WAITQUEUE(wait, current);
> char name[32];
>
> -#ifdef CONFIG_DEVFS_FS
> - sprintf(name, tty->driver.name, minor(tty->device) - tty->driver.minor_start);
> -#else
> - sprintf(name, "%s%d", tty->driver.name, minor(tty->device) - tty->driver.minor_start);
> -#endif
> -
> serio_register_port(&serport->serio);
>
> - printk(KERN_INFO "serio: Serial port %s\n", name);
> -
> - add_wait_queue(&serport->wait, &wait);
> - set_current_state(TASK_INTERRUPTIBLE);
> -
> - while(serport->serio.type && !signal_pending(current)) schedule();
> + printk(KERN_INFO "serio: Serial port %s\n", tty_name(tty, name));
>
> - set_current_state(TASK_RUNNING);
> - remove_wait_queue(&serport->wait, &wait);
> + wait_event_interruptible(serport->wait, serport->serio.type != 0);
>
> serio_unregister_port(&serport->serio);
>

--
Vojtech Pavlik
SuSE Labs
-
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