Re: [PATCH] samples: bpf: fix: seg fault with NULL pointer arg

[Song Liu]

On Sat, Dec 1, 2018 at 1:07 PM Daniel T. Lee  wrote:
>
> When NULL pointer accidentally passed to write_kprobe_events,
> due to strlen(NULL), segmentation fault happens.
> Changed code returns -1 to deal with this situation.
>
> Bug issued with Smatch, static analysis.
>
> Signed-off-by: Daniel T. Lee 
> ---
>  samples/bpf/bpf_load.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/samples/bpf/bpf_load.c b/samples/bpf/bpf_load.c
> index 434ea34a5954..c670bd2200d2 100644
> --- a/samples/bpf/bpf_load.c
> +++ b/samples/bpf/bpf_load.c
> @@ -58,7 +58,9 @@ static int write_kprobe_events(const char *val)
>  {
> int fd, ret, flags;
>
> -   if ((val != NULL) && (val[0] == '\0'))
> +   if (val == NULL)
> +   return -1;
> +   else if ((val != NULL) && (val[0] == '\0'))

We only need
+   else if (val[0] == '\0')
right?

Thanks,
Song

[PATCH] samples: bpf: fix: seg fault with NULL pointer arg

[Daniel T. Lee]

When NULL pointer accidentally passed to write_kprobe_events,
due to strlen(NULL), segmentation fault happens.
Changed code returns -1 to deal with this situation.

Bug issued with Smatch, static analysis.

Signed-off-by: Daniel T. Lee 
---
 samples/bpf/bpf_load.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/samples/bpf/bpf_load.c b/samples/bpf/bpf_load.c
index 434ea34a5954..c670bd2200d2 100644
--- a/samples/bpf/bpf_load.c
+++ b/samples/bpf/bpf_load.c
@@ -58,7 +58,9 @@ static int write_kprobe_events(const char *val)
 {
int fd, ret, flags;
 
-   if ((val != NULL) && (val[0] == '\0'))
+   if (val == NULL)
+   return -1;
+   else if ((val != NULL) && (val[0] == '\0'))
flags = O_WRONLY | O_TRUNC;
else
flags = O_WRONLY | O_APPEND;
-- 
2.17.1