netdev - Re: [PATCH v1 net] tcp: Clear req->syncookie in reqsk

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Message-ID: <8aa1b70e-deb9-4e49-9a6c-059330995384@linux.dev>
Date: Mon, 18 Mar 2024 10:45:01 -0700
From: Martin KaFai Lau <martin.lau@...ux.dev>
To: Kuniyuki Iwashima <kuniyu@...zon.com>
Cc: Martin KaFai Lau <martin.lau@...nel.org>,
 Kuniyuki Iwashima <kuni1840@...il.com>, netdev@...r.kernel.org,
 syzkaller <syzkaller@...glegroups.com>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH v1 net] tcp: Clear req->syncookie in reqsk_alloc().

On 3/15/24 3:47 PM, Kuniyuki Iwashima wrote:
> syzkaller reported a read of uninit req->syncookie. [0]
> 
> Originally, req->syncookie was used only in tcp_conn_request()
> to indicate if we need to encode SYN cookie in SYN+ACK, so the
> field remains uninitialised in other places.
> 
> The commit 695751e31a63 ("bpf: tcp: Handle BPF SYN Cookie in
> cookie_v[46]_check().") added another meaning in ACK path;
> req->syncookie is set true if SYN cookie is validated by BPF
> kfunc.
> 
> After the change, cookie_v[46]_check() always read req->syncookie,
> but it is not initialised in the normal SYN cookie case as reported
> by KMSAN.
> 
> Let's make sure we always initialise req->syncookie in reqsk_alloc().

Acked-by: Martin KaFai Lau <martin.lau@...nel.org>