linux-kernel - [PATCH 23/24] perf cpumap: Fix snprintf overflow check

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Date:   Wed, 25 Mar 2020 09:41:23 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     Jiri Olsa <jolsa@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
        Clark Williams <williams@...hat.com>,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        David Laight <David.Laight@...LAB.COM>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Don Zickus <dzickus@...hat.com>, He Zhe <zhe.he@...driver.com>,
        Jan Stancek <jstancek@...hat.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Mark Rutland <mark.rutland@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        kernel-janitors@...r.kernel.org,
        Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: [PATCH 23/24] perf cpumap: Fix snprintf overflow check

From: Christophe JAILLET <christophe.jaillet@...adoo.fr>

'snprintf' returns the number of characters which would be generated for
the given input.

If the returned value is *greater than* or equal to the buffer size, it
means that the output has been truncated.

Fix the overflow test accordingly.

Fixes: 7780c25bae59f ("perf tools: Allow ability to map cpus to nodes easily")
Fixes: 92a7e1278005b ("perf cpumap: Add cpu__max_present_cpu()")
Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
Suggested-by: David Laight <David.Laight@...LAB.COM>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Don Zickus <dzickus@...hat.com>
Cc: He Zhe <zhe.he@...driver.com>
Cc: Jan Stancek <jstancek@...hat.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Kan Liang <kan.liang@...ux.intel.com>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: kernel-janitors@...r.kernel.org
Link: http://lore.kernel.org/lkml/20200324070319.10901-1-christophe.jaillet@wanadoo.fr
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/util/cpumap.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/cpumap.c b/tools/perf/util/cpumap.c
index 983b7388f22b..dc5c5e6fc502 100644
--- a/tools/perf/util/cpumap.c
+++ b/tools/perf/util/cpumap.c
@@ -317,7 +317,7 @@ static void set_max_cpu_num(void)
 
 	/* get the highest possible cpu number for a sparse allocation */
 	ret = snprintf(path, PATH_MAX, "%s/devices/system/cpu/possible", mnt);
-	if (ret == PATH_MAX) {
+	if (ret >= PATH_MAX) {
 		pr_err("sysfs path crossed PATH_MAX(%d) size\n", PATH_MAX);
 		goto out;
 	}
@@ -328,7 +328,7 @@ static void set_max_cpu_num(void)
 
 	/* get the highest present cpu number for a sparse allocation */
 	ret = snprintf(path, PATH_MAX, "%s/devices/system/cpu/present", mnt);
-	if (ret == PATH_MAX) {
+	if (ret >= PATH_MAX) {
 		pr_err("sysfs path crossed PATH_MAX(%d) size\n", PATH_MAX);
 		goto out;
 	}
@@ -356,7 +356,7 @@ static void set_max_node_num(void)
 
 	/* get the highest possible cpu number for a sparse allocation */
 	ret = snprintf(path, PATH_MAX, "%s/devices/system/node/possible", mnt);
-	if (ret == PATH_MAX) {
+	if (ret >= PATH_MAX) {
 		pr_err("sysfs path crossed PATH_MAX(%d) size\n", PATH_MAX);
 		goto out;
 	}
@@ -441,7 +441,7 @@ int cpu__setup_cpunode_map(void)
 		return 0;
 
 	n = snprintf(path, PATH_MAX, "%s/devices/system/node", mnt);
-	if (n == PATH_MAX) {
+	if (n >= PATH_MAX) {
 		pr_err("sysfs path crossed PATH_MAX(%d) size\n", PATH_MAX);
 		return -1;
 	}
@@ -456,7 +456,7 @@ int cpu__setup_cpunode_map(void)
 			continue;
 
 		n = snprintf(buf, PATH_MAX, "%s/%s", path, dent1->d_name);
-		if (n == PATH_MAX) {
+		if (n >= PATH_MAX) {
 			pr_err("sysfs path crossed PATH_MAX(%d) size\n", PATH_MAX);
 			continue;
 		}
-- 
2.21.1