* [PATCH] printk: fix discarding message when recursion_bug
@ 2008-12-19 18:23 Hiroshi Shimamoto
2008-12-19 21:53 ` Ingo Molnar
0 siblings, 1 reply; 4+ messages in thread
From: Hiroshi Shimamoto @ 2008-12-19 18:23 UTC (permalink / raw)
To: Ingo Molnar; +Cc: Toshikazu Nakayama, linux-kernel
From: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Impact: fix
When recursion_bug is true, kernel discards original message because printk_buf
contains recursion_bug_msg with NULL terminator. The sizeof(recursion_bug_msg)
makes this, use strlen() to get correct length without NULL terminator.
Reported-by: Toshikazu Nakayama <nakayama.ts@ncos.nec.co.jp>
Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
---
kernel/printk.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/kernel/printk.c b/kernel/printk.c
index f492f15..e651ab0 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -662,7 +662,7 @@ asmlinkage int vprintk(const char *fmt, va_list args)
if (recursion_bug) {
recursion_bug = 0;
strcpy(printk_buf, recursion_bug_msg);
- printed_len = sizeof(recursion_bug_msg);
+ printed_len = strlen(recursion_bug_msg);
}
/* Emit the output into the temporary buffer */
printed_len += vscnprintf(printk_buf + printed_len,
--
1.6.0.4
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] printk: fix discarding message when recursion_bug
2008-12-19 18:23 [PATCH] printk: fix discarding message when recursion_bug Hiroshi Shimamoto
@ 2008-12-19 21:53 ` Ingo Molnar
2008-12-19 22:16 ` Hiroshi Shimamoto
0 siblings, 1 reply; 4+ messages in thread
From: Ingo Molnar @ 2008-12-19 21:53 UTC (permalink / raw)
To: Hiroshi Shimamoto; +Cc: Toshikazu Nakayama, linux-kernel
* Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> wrote:
> From: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
>
> Impact: fix
>
> When recursion_bug is true, kernel discards original message because printk_buf
> contains recursion_bug_msg with NULL terminator. The sizeof(recursion_bug_msg)
> makes this, use strlen() to get correct length without NULL terminator.
>
> Reported-by: Toshikazu Nakayama <nakayama.ts@ncos.nec.co.jp>
> Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
> ---
> kernel/printk.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
Good one - applied to tip/core/printk, thanks!
Btw., i'm curious: in what situation was such recursion observed, and how
did the kernel behave? You saw a truncated recursion message in dmesg - or
was it worse?
Ingo
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] printk: fix discarding message when recursion_bug
2008-12-19 21:53 ` Ingo Molnar
@ 2008-12-19 22:16 ` Hiroshi Shimamoto
2008-12-19 22:35 ` Ingo Molnar
0 siblings, 1 reply; 4+ messages in thread
From: Hiroshi Shimamoto @ 2008-12-19 22:16 UTC (permalink / raw)
To: Ingo Molnar; +Cc: Toshikazu Nakayama, linux-kernel
Ingo Molnar wrote:
> * Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> wrote:
>
>> From: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
>>
>> Impact: fix
>>
>> When recursion_bug is true, kernel discards original message because printk_buf
>> contains recursion_bug_msg with NULL terminator. The sizeof(recursion_bug_msg)
>> makes this, use strlen() to get correct length without NULL terminator.
>>
>> Reported-by: Toshikazu Nakayama <nakayama.ts@ncos.nec.co.jp>
>> Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
>> ---
>> kernel/printk.c | 2 +-
>> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> Good one - applied to tip/core/printk, thanks!
>
> Btw., i'm curious: in what situation was such recursion observed, and how
> did the kernel behave? You saw a truncated recursion message in dmesg - or
> was it worse?
I'm not sure about the real situation. I've heard this issue was found in
printing messages in NMI handler, maybe with artificial kernel stuck.
Thanks,
Hiroshi
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] printk: fix discarding message when recursion_bug
2008-12-19 22:16 ` Hiroshi Shimamoto
@ 2008-12-19 22:35 ` Ingo Molnar
0 siblings, 0 replies; 4+ messages in thread
From: Ingo Molnar @ 2008-12-19 22:35 UTC (permalink / raw)
To: Hiroshi Shimamoto; +Cc: Toshikazu Nakayama, linux-kernel
* Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> wrote:
> Ingo Molnar wrote:
> > * Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> wrote:
> >
> >> From: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
> >>
> >> Impact: fix
> >>
> >> When recursion_bug is true, kernel discards original message because printk_buf
> >> contains recursion_bug_msg with NULL terminator. The sizeof(recursion_bug_msg)
> >> makes this, use strlen() to get correct length without NULL terminator.
> >>
> >> Reported-by: Toshikazu Nakayama <nakayama.ts@ncos.nec.co.jp>
> >> Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
> >> ---
> >> kernel/printk.c | 2 +-
> >> 1 files changed, 1 insertions(+), 1 deletions(-)
> >
> > Good one - applied to tip/core/printk, thanks!
> >
> > Btw., i'm curious: in what situation was such recursion observed, and how
> > did the kernel behave? You saw a truncated recursion message in dmesg - or
> > was it worse?
>
> I'm not sure about the real situation. I've heard this issue was found
> in printing messages in NMI handler, maybe with artificial kernel stuck.
yeah, accidental NMI recursion back into printk could indeed cause the
recursion message to pop up.
Ingo
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2008-12-19 22:36 UTC | newest]
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2008-12-19 18:23 [PATCH] printk: fix discarding message when recursion_bug Hiroshi Shimamoto
2008-12-19 21:53 ` Ingo Molnar
2008-12-19 22:16 ` Hiroshi Shimamoto
2008-12-19 22:35 ` Ingo Molnar
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