linux-kernel - [PATCH 5.19 0392/1157] selftests/bpf: Fix rare segfault in sock

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Date:   Mon, 15 Aug 2022 19:55:48 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Jörn-Thorben Hinz <jthinz@...lbox.tu-berlin.de>,
        Andrii Nakryiko <andrii@...nel.org>,
        Jakub Sitnicki <jakub@...udflare.com>,
        Martin KaFai Lau <kafai@...com>,
        John Fastabend <john.fastabend@...il.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.19 0392/1157] selftests/bpf: Fix rare segfault in sock_fields prog test

From: Jörn-Thorben Hinz <jthinz@...lbox.tu-berlin.de>

[ Upstream commit 6dc7a0baf1a70b7d22662d38481824c14ddd80c5 ]

test_sock_fields__detach() got called with a null pointer here when one
of the CHECKs or ASSERTs up to the test_sock_fields__open_and_load()
call resulted in a jump to the "done" label.

A skeletons *__detach() is not safe to call with a null pointer, though.
This led to a segfault.

Go the easy route and only call test_sock_fields__destroy() which is
null-pointer safe and includes detaching.

Came across this while looking[1] to introduce the usage of
bpf_tcp_helpers.h (included in progs/test_sock_fields.c) together with
vmlinux.h.

[1] https://lore.kernel.org/bpf/629bc069dd807d7ac646f836e9dca28bbc1108e2.camel@mailbox.tu-berlin.de/

Fixes: 8f50f16ff39d ("selftests/bpf: Extend verifier and bpf_sock tests for dst_port loads")
Signed-off-by: Jörn-Thorben Hinz <jthinz@...lbox.tu-berlin.de>
Signed-off-by: Andrii Nakryiko <andrii@...nel.org>
Reviewed-by: Jakub Sitnicki <jakub@...udflare.com>
Reviewed-by: Martin KaFai Lau <kafai@...com>
Acked-by: John Fastabend <john.fastabend@...il.com>
Link: https://lore.kernel.org/bpf/20220621070116.307221-1-jthinz@mailbox.tu-berlin.de
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 tools/testing/selftests/bpf/prog_tests/sock_fields.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/sock_fields.c b/tools/testing/selftests/bpf/prog_tests/sock_fields.c
index 9d211b5c22c4..7d23166c77af 100644
--- a/tools/testing/selftests/bpf/prog_tests/sock_fields.c
+++ b/tools/testing/selftests/bpf/prog_tests/sock_fields.c
@@ -394,7 +394,6 @@ void serial_test_sock_fields(void)
 	test();
 
 done:
-	test_sock_fields__detach(skel);
 	test_sock_fields__destroy(skel);
 	if (child_cg_fd >= 0)
 		close(child_cg_fd);
-- 
2.35.1