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([110.93.227.54]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-82739ff1ccasm1483485b3a.39.2026.02.25.23.58.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 Feb 2026 23:58:11 -0800 (PST) From: Zeeshan Ahmad To: Sridhar Samudrala , "David S . Miller" , Jakub Kicinski , Paolo Abeni , Eric Dumazet Cc: netdev@vger.kernel.org, kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org, Simon Horman , Zeeshan Ahmad Subject: [PATCH net v2] net: core: failover: fix NULL pointer dereference in failover_slave_register() Date: Thu, 26 Feb 2026 12:57:37 +0500 Message-ID: <20260226075737.8948-1-zeeshanahmad022019@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: kernel-janitors@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Smatch warns that 'fops' is dereferenced at line 69 without a NULL check. While other callbacks in this function properly check 'fops', the rx_handler registration does not. If failover_get_bymac() returns a valid failover_dev but a NULL fops, the kernel will encounter a NULL pointer dereference when registering the rx_handler. Following the pattern of other failover callers, add a WARN_ON_ONCE() to catch this misconfiguration. Abort the registration if fops is missing to prevent an inconsistent state where a slave is logically linked to a master but lacks a functional data path hook. Fixes: 30c8bd5aa8b2 ("net: Introduce generic failover module") Signed-off-by: Zeeshan Ahmad --- v2: - Target 'net' tree as this is a bug fix. - Change logic from an early return (v1) to WARN_ON_ONCE() and abort registration to prevent inconsistent state, as discussed with Simon Horman. - Update commit message with detailed impact analysis. net/core/failover.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/net/core/failover.c b/net/core/failover.c index 2a140b3ea669..1702bb1feca1 100644 --- a/net/core/failover.c +++ b/net/core/failover.c @@ -63,6 +63,9 @@ static int failover_slave_register(struct net_device *slave_dev) fops->slave_pre_register(slave_dev, failover_dev)) goto done; + if (WARN_ON_ONCE(!fops)) + goto done; + err = netdev_rx_handler_register(slave_dev, fops->slave_handle_frame, failover_dev); if (err) { -- 2.43.0