netdev - [PATCH] net/smc: Fix traversal in __pnet_find_base

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Message-ID: <20250127201408.14869-1-asharji1828@gmail.com>
Date: Tue, 28 Jan 2025 00:14:08 +0400
From: Abdullah <asharji1828@...il.com>
To: syzkaller-bugs@...glegroups.com
Cc: netdev@...r.kernel.org,
	skhan@...uxfoundation.org,
	Abdullah <asharji1828@...il.com>
Subject: [PATCH] net/smc: Fix traversal in __pnet_find_base_ndev

This patch improves the robustness of the function __pnet_find_base_ndev
by:
1. Adding input validation for a NULL `ndev` pointer.
2. Ensuring the function exits gracefully if `netdev_lower_get_next`
   returns NULL during traversal.
3. Clarifying the function’s purpose with proper documentation.
4. Removing the redundant `lower = lower->next` statement, which caused
   traversal to skip levels or go beyond the logic intended, potentially
   leading to invalid memory access.

The function now safely traverses the adjacency list of a network
device to find the lowest-level (base) device in the hierarchy.

Signed-off-by: Abdullah AlSharji <asharji1828@...il.com>
---
 net/smc/smc_pnet.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/net/smc/smc_pnet.c b/net/smc/smc_pnet.c
index 716808f374a8..8adcf6a97d30 100644
--- a/net/smc/smc_pnet.c
+++ b/net/smc/smc_pnet.c
@@ -920,6 +920,18 @@ void smc_pnet_exit(void)

 static struct net_device *__pnet_find_base_ndev(struct net_device *ndev)
 {
+	/**
+	 *  __pnet_find_base_ndev - Find the base network device in a hierarchy.
+	 * ndev: Pointer to the starting network device.
+	 * 
+	 * This function traverses the adjacency list of a network device,
+	 * to find the lowest-level (base) network device in the hierarchy.
+	 * 
+	 */
+
+	if (!ndev) 
+        return NULL;
+
 	int i, nest_lvl;

 	ASSERT_RTNL();
@@ -929,9 +941,9 @@ static struct net_device *__pnet_find_base_ndev(struct net_device *ndev)

 		if (list_empty(lower))
 			break;
-		lower = lower->next;
 		ndev = netdev_lower_get_next(ndev, &lower);
 	}
+	
 	return ndev;
 }

-- 
2.43.0