linux-kernel - Re: [PATCH net-next] vsock/test: Extend transport change null-ptr-deref test

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Message-ID: <ndtaldhrxi7vkqw3vidy7yzs3e3td2jf5q7uystv5ctjbcaw2i@lcutm3s5qsfk>
Date: Mon, 24 Nov 2025 12:41:50 +0100
From: Stefano Garzarella <sgarzare@...hat.com>
To: Michal Luczaj <mhal@...x.co>
Cc: virtualization@...ts.linux.dev, netdev@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] vsock/test: Extend transport change
 null-ptr-deref test

On Sun, Nov 23, 2025 at 10:43:59PM +0100, Michal Luczaj wrote:
>syzkaller reported a lockdep lock order inversion warning[1] due to
>commit 687aa0c5581b ("vsock: Fix transport_* TOCTOU"). This was fixed in
>commit f7c877e75352 ("vsock: fix lock inversion in
>vsock_assign_transport()").
>
>Redo syzkaller's repro by piggybacking on a somewhat related test
>implemented in commit 3a764d93385c ("vsock/test: Add test for null ptr
>deref when transport changes").
>
>[1]: https://lore.kernel.org/netdev/68f6cdb0.a70a0220.205af.0039.GAE@google.com/
>
>Signed-off-by: Michal Luczaj <mhal@...x.co>
>---
> tools/testing/vsock/vsock_test.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)

Reviewed-by: Stefano Garzarella <sgarzare@...hat.com>

>
>diff --git a/tools/testing/vsock/vsock_test.c b/tools/testing/vsock/vsock_test.c
>index d4517386e551..9e1250790f33 100644
>--- a/tools/testing/vsock/vsock_test.c
>+++ b/tools/testing/vsock/vsock_test.c
>@@ -2015,6 +2015,11 @@ static void test_stream_transport_change_client(const struct test_opts *opts)
> 			exit(EXIT_FAILURE);
> 		}
>
>+		/* Although setting SO_LINGER does not affect the original test
>+		 * for null-ptr-deref, it may trigger a lockdep warning.
>+		 */
>+		enable_so_linger(s, 1);
>+
> 		ret = connect(s, (struct sockaddr *)&sa, sizeof(sa));
> 		/* The connect can fail due to signals coming from the thread,
> 		 * or because the receiver connection queue is full.
>@@ -2352,7 +2357,7 @@ static struct test_case test_cases[] = {
> 		.run_server = test_stream_nolinger_server,
> 	},
> 	{
>-		.name = "SOCK_STREAM transport change null-ptr-deref",
>+		.name = "SOCK_STREAM transport change null-ptr-deref, lockdep warn",
> 		.run_client = test_stream_transport_change_client,
> 		.run_server = test_stream_transport_change_server,
> 	},
>
>---
>base-commit: 73138ebe792b9af2954292cc5cfa780a5e796d97
>change-id: 20251121-vsock_test-linger-lockdep-warn-e4c5b8dea5e0
>
>Best regards,
>-- 
>Michal Luczaj <mhal@...x.co>
>