perf cpumap: Fix snprintf overflow check

'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@wanadoo.fr>
Suggested-by: David Laight <David.Laight@ACULAB.COM>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: He Zhe <zhe.he@windriver.com>
Cc: Jan Stancek <jstancek@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: kernel-janitors@vger.kernel.org
Link: http://lore.kernel.org/lkml/20200324070319.10901-1-christophe.jaillet@wanadoo.fr
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/cpumap.c b/tools/perf/util/cpumap.c
index 983b738..dc5c5e6 100644 (file)
--- 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;
                }