[PATCH v2] tools/perf/util: null-terminate version char array upon error

[PATCH v2] tools/perf/util: null-terminate version char array upon error

[Donald Yandt]

If fgets fails due to any other error besides end-of-file, the version char array may not even be null-terminated.

Signed-off-by: Donald Yandt <donald.yandt@gmail.com>
---
 tools/perf/util/machine.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 3c520baa1..28a9541c4 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -1234,8 +1234,9 @@ static char *get_kernel_version(const char *root_dir)
 	if (!file)
 		return NULL;

-	version[0] = '\0';
 	tmp = fgets(version, sizeof(version), file);
+	if (!tmp)
+		*version = '\0';
 	fclose(file);

 	name = strstr(version, prefix);
--
2.20.1

Re: [PATCH v2] tools/perf/util: null-terminate version char array upon error

[Arnaldo Carvalho de Melo]

Em Tue, May 14, 2019 at 07:01:00AM -0400, Donald Yandt escreveu:
> If fgets fails due to any other error besides end-of-file, the version char array may not even be null-terminated.

Thanks, but out of curiosity, was this found just by visual inspection?
Some static analysis tool? An actual problem you stumbled when
processing some /proc/version in a custom kernel?

Also please consider adding a:

Fixes: a1645ce12adb ("perf: 'perf kvm' tool for monitoring guest performance from host")

So that we can get this picked up by the stable kernel trees. I'm adding
it now.

Thanks!

- Arnaldo
 
> Signed-off-by: Donald Yandt <donald.yandt@gmail.com>
> ---
>  tools/perf/util/machine.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
> index 3c520baa1..28a9541c4 100644
> --- a/tools/perf/util/machine.c
> +++ b/tools/perf/util/machine.c
> @@ -1234,8 +1234,9 @@ static char *get_kernel_version(const char *root_dir)
>  	if (!file)
>  		return NULL;
> 
> -	version[0] = '\0';
>  	tmp = fgets(version, sizeof(version), file);
> +	if (!tmp)
> +		*version = '\0';
>  	fclose(file);
> 
>  	name = strstr(version, prefix);
> --
> 2.20.1

-- 

- Arnaldo

[tip:perf/core] perf machine: Null-terminate version char array upon fgets(/proc/version) error

[tip-bot for Donald Yandt]

Commit-ID:  30ba5b0e66c872faa416a458d32cc3956ecb548a
Gitweb:     https://git.kernel.org/tip/30ba5b0e66c872faa416a458d32cc3956ecb548a
Author:     Donald Yandt <donald.yandt@gmail.com>
AuthorDate: Tue, 14 May 2019 07:01:00 -0400
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Wed, 15 May 2019 16:36:47 -0300

perf machine: Null-terminate version char array upon fgets(/proc/version) error

If fgets() fails due to any other error besides end-of-file, the version
char array may not even be null-terminated.

Signed-off-by: Donald Yandt <donald.yandt@gmail.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Avi Kivity <avi@scylladb.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Yanmin Zhang <yanmin_zhang@linux.intel.com>
Fixes: a1645ce12adb ("perf: 'perf kvm' tool for monitoring guest performance from host")
Link: http://lkml.kernel.org/r/20190514110100.22019-1-donald.yandt@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/machine.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 3c520baa198c..28a9541c4835 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -1234,8 +1234,9 @@ static char *get_kernel_version(const char *root_dir)
 	if (!file)
 		return NULL;
 
-	version[0] = '\0';
 	tmp = fgets(version, sizeof(version), file);
+	if (!tmp)
+		*version = '\0';
 	fclose(file);
 
 	name = strstr(version, prefix);