linux-kernel - AW: [PATCH] tools: net: traceevent: Fix 'snprintf' return value check in 'tep_filter

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Date:   Thu, 15 Oct 2020 15:12:53 +0000
From:   Walter Harms <wharms@....de>
To:     Fedor Tokarev <ftokarev@...il.com>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "acme@...hat.com" <acme@...hat.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kernel-janitors@...r.kernel.org" <kernel-janitors@...r.kernel.org>
Subject: AW: [PATCH] tools: net: traceevent: Fix 'snprintf' return value check
 in 'tep_filter_strerror'

i guess the whole thing can be made more simple 

we have len and buflen

len=strlen(filter->error_buffer);
if (len >= buflen )
  return -1;

strcpy(buf, filter->error_buffer);

jm2c,


________________________________________
Von: Fedor Tokarev [ftokarev@...il.com]
Gesendet: Donnerstag, 15. Oktober 2020 16:30
An: rostedt@...dmis.org; acme@...hat.com
Cc: linux-kernel@...r.kernel.org; kernel-janitors@...r.kernel.org; ftokarev@...il.com
Betreff: [PATCH] tools: net: traceevent: Fix 'snprintf' return value check in 'tep_filter_strerror'

'snprintf' returns the number of characters which would have been written
if enough space had been available, excluding the terminating null byte.
Thus, the return value of 'buflen' means that the last character
was dropped.

Signed-off-by: Fedor Tokarev <ftokarev@...il.com>
---
 tools/lib/traceevent/parse-filter.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/lib/traceevent/parse-filter.c b/tools/lib/traceevent/parse-filter.c
index c271aee..dccdbf2 100644
--- a/tools/lib/traceevent/parse-filter.c
+++ b/tools/lib/traceevent/parse-filter.c
@@ -1374,7 +1374,7 @@ int tep_filter_strerror(struct tep_event_filter *filter, enum tep_errno err,
        if (strlen(filter->error_buffer) > 0) {
                size_t len = snprintf(buf, buflen, "%s", filter->error_buffer);

-               if (len > buflen)
+               if (len >= buflen)
                        return -1;
                return 0;
        }
--
2.7.4