2018-03-28 14:11:34

by Arnd Bergmann

Subject: [PATCH] tracing: avoid string overflow

'err' is used as a NUL-terminated string, but using strncpy() with the length
equal to the buffer size may result in lack of the termination:

kernel/trace/trace_events_hist.c: In function 'hist_err_event':
kernel/trace/trace_events_hist.c:396:3: error: 'strncpy' specified bound 256 equals destination size [-Werror=stringop-truncation]
strncpy(err, var, MAX_FILTER_STR_VAL);

This changes it to use the safer strscpy() instead.

Fixes: f404da6e1d46 ("tracing: Add 'last error' error facility for hist triggers")
Signed-off-by: Arnd Bergmann <[email protected]>
---
kernel/trace/trace_events_hist.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 4f027642ceef..8357f36d7a1e 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -393,7 +393,7 @@ static void hist_err_event(char *str, char *system, char *event, char *var)
else if (system)
snprintf(err, MAX_FILTER_STR_VAL, "%s.%s", system, event);
else
- strncpy(err, var, MAX_FILTER_STR_VAL);
+ strscpy(err, var, MAX_FILTER_STR_VAL);

hist_err(str, err);
}
--
2.9.0

2018-03-28 16:09:51

by Tom Zanussi

Subject: Re: [PATCH] tracing: avoid string overflow

Hi Arnd,

On Wed, 2018-03-28 at 16:09 +0200, Arnd Bergmann wrote:
> 'err' is used as a NUL-terminated string, but using strncpy() with the length
> equal to the buffer size may result in lack of the termination:
>
> kernel/trace/trace_events_hist.c: In function 'hist_err_event':
> kernel/trace/trace_events_hist.c:396:3: error: 'strncpy' specified bound 256 equals destination size [-Werror=stringop-truncation]
> strncpy(err, var, MAX_FILTER_STR_VAL);
>
> This changes it to use the safer strscpy() instead.
>
> Fixes: f404da6e1d46 ("tracing: Add 'last error' error facility for hist triggers")
> Signed-off-by: Arnd Bergmann <[email protected]>
> ---
> kernel/trace/trace_events_hist.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> index 4f027642ceef..8357f36d7a1e 100644
> --- a/kernel/trace/trace_events_hist.c
> +++ b/kernel/trace/trace_events_hist.c
> @@ -393,7 +393,7 @@ static void hist_err_event(char *str, char *system, char *event, char *var)
> else if (system)
> snprintf(err, MAX_FILTER_STR_VAL, "%s.%s", system, event);
> else
> - strncpy(err, var, MAX_FILTER_STR_VAL);
> + strscpy(err, var, MAX_FILTER_STR_VAL);
>
> hist_err(str, err);
> }

Yes, thanks for finding this, and for the patch!

Acked-by: Tom Zanussi <[email protected]>

2018-04-02 15:29:31

by Steven Rostedt

Subject: Re: [PATCH] tracing: avoid string overflow

On Wed, 28 Mar 2018 16:09:10 +0200
Arnd Bergmann <[email protected]> wrote:

> 'err' is used as a NUL-terminated string, but using strncpy() with the length
> equal to the buffer size may result in lack of the termination:
>
> kernel/trace/trace_events_hist.c: In function 'hist_err_event':
> kernel/trace/trace_events_hist.c:396:3: error: 'strncpy' specified bound 256 equals destination size [-Werror=stringop-truncation]
> strncpy(err, var, MAX_FILTER_STR_VAL);
>
> This changes it to use the safer strscpy() instead.
>
> Fixes: f404da6e1d46 ("tracing: Add 'last error' error facility for hist triggers")
> Signed-off-by: Arnd Bergmann <[email protected]>

Thanks! I pulled this in and will push it to git after testing has
succeeded.

-- Steve

> ---
> kernel/trace/trace_events_hist.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> index 4f027642ceef..8357f36d7a1e 100644
> --- a/kernel/trace/trace_events_hist.c
> +++ b/kernel/trace/trace_events_hist.c
> @@ -393,7 +393,7 @@ static void hist_err_event(char *str, char *system, char *event, char *var)
> else if (system)
> snprintf(err, MAX_FILTER_STR_VAL, "%s.%s", system, event);
> else
> - strncpy(err, var, MAX_FILTER_STR_VAL);
> + strscpy(err, var, MAX_FILTER_STR_VAL);
>
> hist_err(str, err);
> }