linux-kernel - [PATCH AUTOSEL 5.8 40/64] bpf: Fix fds

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Date:   Mon, 10 Aug 2020 15:08:35 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Wenbo Zhang <ethercflow@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andriin@...com>,
        Sasha Levin <sashal@...nel.org>, netdev@...r.kernel.org,
        bpf@...r.kernel.org
Subject: [PATCH AUTOSEL 5.8 40/64] bpf: Fix fds_example SIGSEGV error

From: Wenbo Zhang <ethercflow@...il.com>

[ Upstream commit eef8a42d6ce087d1c81c960ae0d14f955b742feb ]

The `BPF_LOG_BUF_SIZE`'s value is `UINT32_MAX >> 8`, so define an array
with it on stack caused an overflow.

Signed-off-by: Wenbo Zhang <ethercflow@...il.com>
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Acked-by: Andrii Nakryiko <andriin@...com>
Link: https://lore.kernel.org/bpf/20200710092035.28919-1-ethercflow@gmail.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 samples/bpf/fds_example.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/samples/bpf/fds_example.c b/samples/bpf/fds_example.c
index d5992f7872328..59f45fef51109 100644
--- a/samples/bpf/fds_example.c
+++ b/samples/bpf/fds_example.c
@@ -30,6 +30,8 @@
 #define BPF_M_MAP	1
 #define BPF_M_PROG	2
 
+char bpf_log_buf[BPF_LOG_BUF_SIZE];
+
 static void usage(void)
 {
 	printf("Usage: fds_example [...]\n");
@@ -57,7 +59,6 @@ static int bpf_prog_create(const char *object)
 		BPF_EXIT_INSN(),
 	};
 	size_t insns_cnt = sizeof(insns) / sizeof(struct bpf_insn);
-	char bpf_log_buf[BPF_LOG_BUF_SIZE];
 	struct bpf_object *obj;
 	int prog_fd;
 
-- 
2.25.1