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Subject[PATCH V2] perf cpumap: Fix snprintf overflow check
Date
'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 accordingling.

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>
---
V2: keep snprintf
modifiy the tests for truncated output
Update subject and description
---
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;
}
--
2.20.1
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