From: Jakub Kicinski <kuba@kernel.org>
To: Xiang Mei <xmei5@asu.edu>
Cc: netdev@vger.kernel.org, davem@davemloft.net, edumazet@google.com,
pabeni@redhat.com, horms@kernel.org, bestswngs@gmail.com
Subject: Re: [PATCH net] udp_tunnel: fix NULL deref caused by udp_sock_create6 when CONFIG_IPV6=n
Date: Mon, 16 Mar 2026 17:06:09 -0700 [thread overview]
Message-ID: <20260316170609.6636d621@kernel.org> (raw)
In-Reply-To: <20260316005337.1147633-1-xmei5@asu.edu>
On Sun, 15 Mar 2026 17:53:37 -0700 Xiang Mei wrote:
> When CONFIG_IPV6 is disabled, the udp_sock_create6() function returns 0
> (success) without actually creating a socket. Callers such as
> fou_create() then proceed to dereference the uninitialized socket
> pointer, resulting in a NULL pointer dereference.
>
> Return -EPFNOSUPPORT instead, so callers correctly take their error
> paths. There is only one caller of the vulnerable function and only
> privileged users can trigger it.
>
> The captured NULL deref crash:
> [ 0.489638] BUG: kernel NULL pointer dereference, address: 0000000000000018
> [ 0.489962] #PF: supervisor read access in kernel mode
> [ 0.490193] #PF: error_code(0x0000) - not-present page
> [ 0.490435] PGD 102a11067 P4D 102a11067 PUD 102a12067 PMD 0
> [ 0.490706] Oops: Oops: 0000 [#1] SMP NOPTI
> [ 0.490905] CPU: 0 UID: 0 PID: 140 Comm: exploit Not tainted 7.0.0-rc3+ #2 PREEMPTLAZY
> [ 0.491266] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.17.0-0-gb52ca86e094d-prebuilt.qemu.org 04/01/2014
> [ 0.491786] RIP: 0010:fou_nl_add_doit (net/ipv4/fou_core.c:590 net/ipv4/fou_core.c:764)
> [ 0.492009] Code: c5 48 85 c0 0f 84 04 02 00 00 48 8b 34 24 0f b7 44 24 1c 4c 8d 44 24 30 b9 07 00 00 00 0f b7 54 24 0c 4c 89 c7 48 89 6c 24 28 <4c> 8b 6e 18 66 89 45 0a 0f b6 44 24 10 66 89 55 0e 48 89 75 00 88
> All code
> ========
Please trim the crash dump to what is relevant.
--
pw-bot: cr
next prev parent reply other threads:[~2026-03-17 0:06 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-16 0:53 [PATCH net] udp_tunnel: fix NULL deref caused by udp_sock_create6 when CONFIG_IPV6=n Xiang Mei
2026-03-16 0:56 ` Xiang Mei
2026-03-17 0:06 ` Jakub Kicinski [this message]
2026-03-17 1:04 ` Xiang Mei
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