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 64750352017; Sat, 12 Sep 2026 15:32:15 +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=1789227136; cv=none; b=b76CrLTZz0hZyeGSJ4LZk5CgPBD0zyH042CaoFGBKFg+mPrwlePb+mohJelpxNmyuRKJF6dAjge3EGevMZHv2tLCcbEBS1pokZ2ommB2HjJpD1kjSaeTsKgDjfHQqqoB5wjE5b7LvKXORAlSHzqDV7jVNYTMq560vsuwkON/Lsw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789227136; c=relaxed/simple; bh=rw3Qd0gX25ngwW/aa9Aworlsdy9jaVt4iz+1UTMSMdw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=lIv0o9N726Q1WoQ+x7uiQVUyUvrvNADQuS1i2F4qa6Z3zW6JUSSIanJt5rAmtFu84swlKnf/zK9ExGQ3PVFoV/8tBKqWZwAFzsI7aIfkOzP+DdM1fHGaSspFtvjGI7WO2vSEy5z5uFIhzsj8VXiz9YUvKL8zZVHlpUsMgYUvzEg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=TLcG8RjG; 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="TLcG8RjG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 163FD1F00893; Sat, 12 Sep 2026 15:32:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789227135; bh=7mNDWh6zhRYFuISqTIMeOOZiyBVlj6wT5s3DlsevPi0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=TLcG8RjG4PoJsad/FHM5ijaXSQc6IsMVsjv7dimLTjteugT1NeMseO9csxuuFFJTt 45pqsMvys5frHKnfSCmEMpExu8cz952JbXYZlhM7D8cUZTaWcxf1KWCcMNkelfugyq ZrIQ2vW21AhzQ25vUcVZ0i7Fbz9WVjjo+qFTZNWk= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Yuyang Huang , Stefano Brivio , Ido Schimmel , "David S. Miller" , Jakub Kicinski Subject: [PATCH 6.1 0120/1191] ipv6: use RCU iterator to dump route exceptions Date: Sat, 12 Sep 2026 08:47:28 +0200 Message-ID: <20260912065550.885078839@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260912065548.086904252@linuxfoundation.org> References: <20260912065548.086904252@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 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Yuyang Huang commit 47cdab0d51aaa9bd85f8e4904585bd5bd4df4488 upstream. rt6_nh_dump_exceptions() uses hlist_for_each_entry() to iterate over RCU-protected exception lists. The caller holds rcu_read_lock(), but does not hold rt6_exception_lock, so rt6_insert_exception() can concurrently add an entry with hlist_add_head_rcu(). KCSAN reports this race (irrelevant details omitted): ================================================================== BUG: KCSAN: data-race in rt6_insert_exception / rt6_nh_dump_exceptions write (marked) to 0xffff8a7c44c59620 of 8 bytes by interrupt on cpu 5: rt6_insert_exception+0x3bb/0x760 __ip6_rt_update_pmtu+0x4fe/0x750 ip6_sk_update_pmtu+0x19a/0x3b0 udpv6_err+0x3ff/0x800 icmpv6_notify+0x1e1/0x440 icmpv6_rcv+0x8c0/0xab0 ip6_protocol_deliver_rcu+0x616/0x840 ip6_input_finish+0xb9/0x160 ... entry_SYSCALL_64_after_hwframe+0x77/0x7f read to 0xffff8a7c44c59620 of 8 bytes by task 549 on cpu 14: rt6_nh_dump_exceptions+0xb3/0x260 rt6_dump_route+0x53e/0x5f0 fib6_dump_node+0x6d/0xf0 fib6_walk_continue+0x290/0x2d0 fib6_dump_table+0x28d/0x360 inet6_dump_fib+0x37d/0x620 rtnl_dumpit+0x7b/0xd0 netlink_dump+0x3ae/0x7e0 ... entry_SYSCALL_64_after_hwframe+0x77/0x7f 4 locks held by dumper/549: ... #1: (rcu_read_lock){....}-{1:3}, at: inet6_dump_fib+0x88/0x620 #2: (&tb->tb6_lock){+.-.}-{3:3}, at: fib6_dump_table+0x1e9/0x360 #3: (rcu_read_lock){....}-{1:3}, at: rt6_dump_route+0x483/0x5f0 value changed: 0xffff8a7c44e05700 -> 0xffff8a7c45d60100 Reported by Kernel Concurrency Sanitizer on: CPU: 14 UID: 0 PID: 549 Comm: dumper Not tainted 7.2.0-rc7-virtme #38 PREEMPT(lazy) ... Use hlist_for_each_entry_rcu() to safely iterate over the exception list. Fixes: 1e47b4837f3b ("ipv6: Dump route exceptions if requested") Cc: stable@vger.kernel.org Signed-off-by: Yuyang Huang Reviewed-by: Stefano Brivio Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/20260815084651.69477-1-sigefriedhyy@gmail.com Signed-off-by: David S. Miller Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- net/ipv6/route.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -5915,7 +5915,7 @@ static int rt6_nh_dump_exceptions(struct return 0; for (i = 0; i < FIB6_EXCEPTION_BUCKET_SIZE; i++) { - hlist_for_each_entry(rt6_ex, &bucket->chain, hlist) { + hlist_for_each_entry_rcu(rt6_ex, &bucket->chain, hlist) { if (w->skip) { w->skip--; continue;