2014-10-16 19:11:11

by Peter Hurley

Subject: [PATCH] ia64: Pin controlling tty for unaligned fault message

Prevent destruction of the controlling tty before tty_write_message()
can determine if the tty is safe to use.

Signed-off-by: Peter Hurley <[email protected]>
---
arch/ia64/kernel/unaligned.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/ia64/kernel/unaligned.c b/arch/ia64/kernel/unaligned.c
index 622772b..e7ae608 100644
--- a/arch/ia64/kernel/unaligned.c
+++ b/arch/ia64/kernel/unaligned.c
@@ -1336,8 +1336,11 @@ ia64_handle_unaligned (unsigned long ifa, struct pt_regs *regs)
* Don't call tty_write_message() if we're in the kernel; we might
* be holding locks...
*/
- if (user_mode(regs))
- tty_write_message(current->signal->tty, buf);
+ if (user_mode(regs)) {
+ struct tty_struct *tty = get_current_tty();
+ tty_write_message(tty, buf);
+ tty_kref_put(tty);
+ }
buf[len-1] = '\0'; /* drop '\r' */
/* watch for command names containing %s */
printk(KERN_WARNING "%s", buf);
--
2.1.1

2014-10-16 19:12:50

by Peter Hurley

Subject: Re: [PATCH] ia64: Pin controlling tty for unaligned fault message

On 10/16/2014 03:10 PM, Peter Hurley wrote:
> Prevent destruction of the controlling tty before tty_write_message()
> can determine if the tty is safe to use.

This does not make tty_write_message() bulletproof from concurrent
teardown, but that's on my todo list.


> Signed-off-by: Peter Hurley <[email protected]>
> ---
> arch/ia64/kernel/unaligned.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/arch/ia64/kernel/unaligned.c b/arch/ia64/kernel/unaligned.c
> index 622772b..e7ae608 100644
> --- a/arch/ia64/kernel/unaligned.c
> +++ b/arch/ia64/kernel/unaligned.c
> @@ -1336,8 +1336,11 @@ ia64_handle_unaligned (unsigned long ifa, struct pt_regs *regs)
> * Don't call tty_write_message() if we're in the kernel; we might
> * be holding locks...
> */
> - if (user_mode(regs))
> - tty_write_message(current->signal->tty, buf);
> + if (user_mode(regs)) {
> + struct tty_struct *tty = get_current_tty();
> + tty_write_message(tty, buf);
> + tty_kref_put(tty);
> + }
> buf[len-1] = '\0'; /* drop '\r' */
> /* watch for command names containing %s */
> printk(KERN_WARNING "%s", buf);
>