Le 23/03/2020 à 12:03, Dan Carpenter a écrit :
On Sun, Mar 22, 2020 at 06:25:23PM +0100, Christophe JAILLET wrote:
'scnprintf' returns the number of characters written in the output buffer
excluding the trailing '\0', instead of the number of characters which
would be generated for the given input.
Both function return a number of characters, excluding the trailing '\0'.
So comparaison to check if it overflows, should be done against max_size-1.
Comparaison against max_size can never match.
Fixes: 7780c25bae59f ("perf tools: Allow ability to map cpus to nodes easily")
Fixes: a24020e6b7cf6 ("perf tools: Change cpu_map__fprintf output")
Fixes: 92a7e1278005b ("perf cpumap: Add cpu__max_present_cpu()")
Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
---
tools/perf/util/cpumap.c | 39 ++++++++++++++++++++-------------------
1 file changed, 20 insertions(+), 19 deletions(-)
diff --git a/tools/perf/util/cpumap.c b/tools/perf/util/cpumap.c
index 983b7388f22b..b87e7ef4d130 100644
--- a/tools/perf/util/cpumap.c
+++ b/tools/perf/util/cpumap.c
@@ -316,8 +316,8 @@ static void set_max_cpu_num(void)
goto out;
/* 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) {
+ ret = scnprintf(path, PATH_MAX, "%s/devices/system/cpu/possible", mnt);
+ if (ret == PATH_MAX-1) {
This should be a static analysis warning.
But isn't this stuff userspace? I can't figure out how to compile it on
Debian so I'm not sure. There is no scnprintf() in user space.
regards,
dan carpenter
I compiled it with:
make tools/perf
the cpumap.o is generated and if I introduce an error,
'scn<SPACE>printf' for example, gcc triggers a built error.
I though it was enough to validate the patch, before sending it.
Anyway, keeping 'snprintf' could be better to check for the overflow,
but 'if (ret == PATH_MAX)' should be turned in 'if (ret >= PATH_MAX)'.
If agreed, I can send a V2.
CJ
