[PATCH AUTOSEL 5.4 193/330] perf cpumap: Fix snprintf overflow check

[Sasha Levin]

From: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>

[ Upstream commit d74b181a028bb5a468f0c609553eff6a8fdf4887 ]

'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@xxxxxxxxxx>
Suggested-by: David Laight <David.Laight@xxxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Don Zickus <dzickus@xxxxxxxxxx>
Cc: He Zhe <zhe.he@xxxxxxxxxxxxx>
Cc: Jan Stancek <jstancek@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: kernel-janitors@xxxxxxxxxxxxxxx
Link: http://lore.kernel.org/lkml/20200324070319.10901-1-christophe.jaillet@xxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 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 a22c1114e880d..324ec0456c83f 100644
--- a/tools/perf/util/cpumap.c
+++ b/tools/perf/util/cpumap.c
@@ -299,7 +299,7 @@ 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;
 	}
@@ -310,7 +310,7 @@ 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;
 	}
@@ -338,7 +338,7 @@ 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;
 	}
@@ -423,7 +423,7 @@ 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;
 	}
@@ -438,7 +438,7 @@ 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;
 		}
-- 
2.25.1