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SubjectRe: [PATCH] tracing: avoid string overflow
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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 <arnd@arndb.de>
> ---
> 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 <tom.zanussi@linux.intel.com>


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