netdev - [PATCH] net: ipv4: Fix uninitialized pointer warning in fnhe_remove

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Message-Id: <20250417094126.34352-1-purvayeshi550@gmail.com>
Date: Thu, 17 Apr 2025 15:11:26 +0530
From: Purva Yeshi <purvayeshi550@...il.com>
To: "David S . Miller" <davem@...emloft.net>,
	David Ahern <dsahern@...nel.org>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>
Cc: Simon Horman <horms@...nel.org>,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Purva Yeshi <purvayeshi550@...il.com>
Subject: [PATCH] net: ipv4: Fix uninitialized pointer warning in fnhe_remove_oldest

Fix Smatch-detected issue:
net/ipv4/route.c:605 fnhe_remove_oldest() error:
uninitialized symbol 'oldest_p'.

Initialize oldest_p to NULL to avoid uninitialized pointer warning in
fnhe_remove_oldest.

Check that oldest_p is not NULL after the loop to ensure no dereferencing
of uninitialized pointers.

Signed-off-by: Purva Yeshi <purvayeshi550@...il.com>
---
 net/ipv4/route.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 753704f75b2c..2e5159127cb9 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -587,7 +587,7 @@ static void fnhe_flush_routes(struct fib_nh_exception *fnhe)
 
 static void fnhe_remove_oldest(struct fnhe_hash_bucket *hash)
 {
-	struct fib_nh_exception __rcu **fnhe_p, **oldest_p;
+	struct fib_nh_exception __rcu **fnhe_p, **oldest_p = NULL;
 	struct fib_nh_exception *fnhe, *oldest = NULL;
 
 	for (fnhe_p = &hash->chain; ; fnhe_p = &fnhe->fnhe_next) {
@@ -601,9 +601,12 @@ static void fnhe_remove_oldest(struct fnhe_hash_bucket *hash)
 			oldest_p = fnhe_p;
 		}
 	}
-	fnhe_flush_routes(oldest);
-	*oldest_p = oldest->fnhe_next;
-	kfree_rcu(oldest, rcu);
+
+	if (oldest_p) {  /* Ensure to have valid oldest_p element */
+		fnhe_flush_routes(oldest);
+		*oldest_p = oldest->fnhe_next;
+		kfree_rcu(oldest, rcu);
+	}
 }
 
 static u32 fnhe_hashfun(__be32 daddr)
-- 
2.34.1