linux-kernel - Re: [PATCH v4 1/1] net: core: prevent NULL deref in generic_hwtstamp_ioctl

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Message-ID: <20251112094541.5510346b@kmaincent-XPS-13-7390>
Date: Wed, 12 Nov 2025 09:45:41 +0100
From: Kory Maincent <kory.maincent@...tlin.com>
To: Jiaming Zhang <r772577952@...il.com>
Cc: kuba@...nel.org, davem@...emloft.net, edumazet@...gle.com,
 horms@...nel.org, kuniyu@...gle.com, linux-kernel@...r.kernel.org,
 netdev@...r.kernel.org, pabeni@...hat.com, sdf@...ichev.me,
 syzkaller@...glegroups.com, vladimir.oltean@....com
Subject: Re: [PATCH v4 1/1] net: core: prevent NULL deref in
 generic_hwtstamp_ioctl_lower()

On Wed, 12 Nov 2025 01:36:52 +0800
Jiaming Zhang <r772577952@...il.com> wrote:

> The ethtool tsconfig Netlink path can trigger a null pointer
> dereference. A call chain such as:
> 
>   tsconfig_prepare_data() ->
>   dev_get_hwtstamp_phylib() ->
>   vlan_hwtstamp_get() ->
>   generic_hwtstamp_get_lower() ->
>   generic_hwtstamp_ioctl_lower()
> 
> results in generic_hwtstamp_ioctl_lower() being called with
> kernel_cfg->ifr as NULL.
> 
> The generic_hwtstamp_ioctl_lower() function does not expect a
> NULL ifr and dereferences it, leading to a system crash.
> 
> Fix this by adding a NULL check for kernel_cfg->ifr in
> generic_hwtstamp_ioctl_lower(). If ifr is NULL, return -EINVAL.
> 
> Fixes: 6e9e2eed4f39 ("net: ethtool: Add support for tsconfig command to
> get/set hwtstamp config") Closes:
> https://lore.kernel.org/lkml/cd6a7056-fa6d-43f8-b78a-f5e811247ba8@linux.dev/T/#mf5df538e21753e3045de98f25aa18d948be07df3
> 
> Signed-off-by: Jiaming Zhang <r772577952@...il.com>

Reviewed-by: Kory Maincent <kory.maincent@...tlin.com>

Thank you!
-- 
Köry Maincent, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com