linux-kernel - [PATCH AUTOSEL 4.19 030/100] samples: bpf: fix: seg fault with NULL pointer arg

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Message-Id: <20191018220525.9042-30-sashal@kernel.org>
Date:   Fri, 18 Oct 2019 18:04:15 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     "Daniel T. Lee" <danieltimlee@...il.com>,
        Song Liu <songliubraving@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Sasha Levin <sashal@...nel.org>, netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 4.19 030/100] samples: bpf: fix: seg fault with NULL pointer arg

From: "Daniel T. Lee" <danieltimlee@...il.com>

[ 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@...il.com>
Acked-by: Song Liu <songliubraving@...com>
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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