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([123.124.147.27]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-b7128885251sm16003643a12.17.2025.10.30.02.36.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Oct 2025 02:36:28 -0700 (PDT) From: Jiaming Zhang To: kory.maincent@bootlin.com Cc: davem@davemloft.net, edumazet@google.com, horms@kernel.org, kuba@kernel.org, kuniyu@google.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, pabeni@redhat.com, r772577952@gmail.com, sdf@fomichev.me, syzkaller@googlegroups.com, vladimir.oltean@nxp.com, stable@vger.kernel.org Subject: [PATCH] net: core: prevent NULL deref in generic_hwtstamp_ioctl_lower() Date: Thu, 30 Oct 2025 09:36:21 +0000 Message-Id: <20251030093621.3563440-1-r772577952@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20251029110651.25c4936d@kmaincent-XPS-13-7390> References: <20251029110651.25c4936d@kmaincent-XPS-13-7390> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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_get/set_lower(). If ifr is NULL, return -EOPNOTSUPP to prevent the call to the legacy IOCTL helper. 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@l= inux.dev/T/#mf5df538e21753e3045de98f25aa18d948be07df3 Signed-off-by: Jiaming Zhang Reviewed-by: Kory Maincent --- net/core/dev_ioctl.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/net/core/dev_ioctl.c b/net/core/dev_ioctl.c index ad54b12d4b4c..39eaf6ba981a 100644 --- a/net/core/dev_ioctl.c +++ b/net/core/dev_ioctl.c @@ -474,6 +474,10 @@ int generic_hwtstamp_get_lower(struct net_device *dev, return err; } =20 + /* Netlink path with unconverted driver */ + if (!kernel_cfg->ifr) + return -EOPNOTSUPP; + /* Legacy path: unconverted lower driver */ return generic_hwtstamp_ioctl_lower(dev, SIOCGHWTSTAMP, kernel_cfg); } @@ -498,6 +502,10 @@ int generic_hwtstamp_set_lower(struct net_device *dev, return err; } =20 + /* Netlink path with unconverted driver */ + if (!kernel_cfg->ifr) + return -EOPNOTSUPP; + /* Legacy path: unconverted lower driver */ return generic_hwtstamp_ioctl_lower(dev, SIOCSHWTSTAMP, kernel_cfg); } --=20 2.34.1