[PATCH 4.19 037/149] samples: bpf: fix: seg fault with NULL pointer arg

[Greg Kroah-Hartman]

From: Daniel T. Lee <danieltimlee@xxxxxxxxx>

[ Upstream commit d59dd69d5576d699d7d3f5da0b4738c3a36d0133 ]

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 <danieltimlee@xxxxxxxxx>
Acked-by: Song Liu <songliubraving@xxxxxx>
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 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 5061a2ec45646..176c04a454dc9 100644
--- a/samples/bpf/bpf_load.c
+++ b/samples/bpf/bpf_load.c
@@ -59,7 +59,9 @@ 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[0] == '\0')
 		flags = O_WRONLY | O_TRUNC;
 	else
 		flags = O_WRONLY | O_APPEND;
-- 
2.20.1