From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2E1F83B6366; Thu, 30 Jul 2026 14:59:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785423590; cv=none; b=hXwh3LB4uZZ6LGbRsdW/BjCsq3wFX5MSEjw/7kfj9GHH+m1U1c81la9+C0KtQi+wETUuGZADLP6G3ZUJjg7KP9rulhspzq87Jnp6IQjHYncAhqKMjPtlnam4Sah28QJLZ7/VmiCWI6IfSyKWTWV10hIy240La1URsMPSquBiXRY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785423590; c=relaxed/simple; bh=BzQ2/IQkDKIROWvLYFDqWHUarZddqnkHRAbLjKXY3rc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=tzup0b1xsGyi/hwURRSNMIo1lsOUo7/74czUVqSarCVFsHXfvwL2u2GWf3SKLiVIlac0IfnsBZsIjY/9H2EvBmSQpmgQ69W0IlT7ovsEvEvDiKigm+AIt3ylXnkCOLF2AS+9MphDcLMMgjfr64qqICuWUK8AeEKBcsEsUzXAmeI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=fZ7viEqk; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="fZ7viEqk" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8A7851F000E9; Thu, 30 Jul 2026 14:59:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1785423589; bh=vihnDTjsU3SDs3WWN3RpzTojTsxjvqRZBFZ70eh7E2Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=fZ7viEqkWwcTTdnAnEF1jXfFOOVG8IgVJ+oJoSus9k1hUyNFMa+RkrYx4Cz35hCkj 8aox+5kI83RlZiDV630wwMh8oZX7ETvZnnAFnWxgwoKx1qVx+kUKgtYsRYTjMY3zmt xB4hvECqqUQzDi3Me8sPW4DwO0thvwDogjerozaU= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Xiang Mei , Weiming Shi , Ido Schimmel , Paolo Abeni , Sasha Levin Subject: [PATCH 6.18 097/675] ipv4: fib: free fib_alias with kfree_rcu() on insert error path Date: Thu, 30 Jul 2026 16:07:07 +0200 Message-ID: <20260730141447.191971942@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260730141445.110192266@linuxfoundation.org> References: <20260730141445.110192266@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Weiming Shi [ Upstream commit f2f152e94a67bc746afaf05a1b2702c195553112 ] fib_table_insert() publishes new_fa into the leaf's fa_list with fib_insert_alias() before calling the fib entry notifiers. When a notifier fails, the error path removes new_fa with fib_remove_alias() (hlist_del_rcu) and frees it right away with kmem_cache_free(). fib_table_lookup() walks that list under rcu_read_lock() only, so a concurrent lookup that already reached new_fa keeps reading it after the free: BUG: KASAN: slab-use-after-free in fib_table_lookup (net/ipv4/fib_trie.c:1601) Read of size 1 at addr ffff88810676d4eb by task exploit/297 Call Trace: fib_table_lookup (net/ipv4/fib_trie.c:1601) ip_route_output_key_hash_rcu (net/ipv4/route.c:2814) ip_route_output_key_hash (net/ipv4/route.c:2705) __ip4_datagram_connect (net/ipv4/datagram.c:49) udp_connect (net/ipv4/udp.c:2144) __sys_connect (net/socket.c:2167) __x64_sys_connect (net/socket.c:2173) do_syscall_64 entry_SYSCALL_64_after_hwframe which belongs to the cache ip_fib_alias of size 56 Triggering the error path needs CAP_NET_ADMIN and a registered fib notifier that can reject a route; a netdevsim device whose IPv4 FIB resource is exhausted is enough. Free new_fa with alias_free_mem_rcu(), as fib_table_delete() already does for a fib_alias removed from the trie. Fixes: a6c76c17df02 ("ipv4: Notify route after insertion to the routing table") Reported-by: Xiang Mei Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Weiming Shi Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/20260704171421.1786806-1-bestswngs@gmail.com Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin --- net/ipv4/fib_trie.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c index 1308213791f19d..2dc87e2156d373 100644 --- a/net/ipv4/fib_trie.c +++ b/net/ipv4/fib_trie.c @@ -1385,7 +1385,7 @@ int fib_table_insert(struct net *net, struct fib_table *tb, out_remove_new_fa: fib_remove_alias(t, tp, l, new_fa); out_free_new_fa: - kmem_cache_free(fn_alias_kmem, new_fa); + alias_free_mem_rcu(new_fa); out: fib_release_info(fi); err: -- 2.53.0