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 3B8AC3CE481 for ; Tue, 16 Jun 2026 05:13:28 +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=1781586809; cv=none; b=CzkSaCTkeBQ0BiGBbyqc39BpbhcBiYxGvnrhPmRHIX8UJrTQLr1VJf4iOy9u5DSbO3tFOqmtIGp9qwuzPMSsI5Pf6StbcczyPlxXkzemkDx/TjDjoyHYu5T66NDULWfrO11naBkrTTPhjvFOT08h5nWHECSSlJglRujUo+pL7Gg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781586809; c=relaxed/simple; bh=zN+JkfaBed6t14OOxabTV2baYgaRMMqHq5HxTke4brY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=UTb6dIv5le/EX+46tndKf9YXw5WgK1Kl5j+EHvi+CW0kXSJ8HWLwL+55Gq1viHGIpueOAOrCVdAj2+exRmn5qb3YdJUGgGkfnA90f4ISOC82hx4wsjK3X2X5pb153SzCm0YEBwHvkR6ERFDXA1hfo7XKfd3Etf0fW6H8vkgaOuE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=x/wPNSxe; 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="x/wPNSxe" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0874B1F00A3A; Tue, 16 Jun 2026 05:13:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1781586807; bh=+DZga0xTEhJ3ren6f5+cf9c00RoQor9hdjEuv50XnTQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=x/wPNSxeKjbIKaWIISn0triVl7/J/BqXcJDWf25bwL6Up2sXw5fYTpKS7euWXTGgn 4/AVWeMjjd9jdaFBZY+Y3R5MIOPpjkuR4JBdZsEhg1D/nrxtjZpKoq2jbWlHA94J0g mkQpze6xh9Fd+ykR7+VI84urYsYL7OPdrOQsWi7w= Date: Tue, 16 Jun 2026 10:42:23 +0530 From: Greg Kroah-Hartman To: Kevin Berry Cc: xmei5@asu.edu, bestswngs@gmail.com, chenglongtang@google.com, joneslee@google.com, pabeni@redhat.com, rnj@google.com, stable@vger.kernel.org, Sasha Levin Subject: Re: [PATCH] net: bonding: fix use-after-free in bond_xmit_broadcast() Message-ID: <2026061617-flyable-civic-a986@gregkh> References: <20260506202842.1788682-1-kpberry@google.com> <20260506202842.1788682-2-kpberry@google.com> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260506202842.1788682-2-kpberry@google.com> On Wed, May 06, 2026 at 08:28:42PM +0000, Kevin Berry wrote: > From: Xiang Mei > > commit 2884bf72fb8f03409e423397319205de48adca16 upstream. > > bond_xmit_broadcast() reuses the original skb for the last slave > (determined by bond_is_last_slave()) and clones it for others. > Concurrent slave enslave/release can mutate the slave list during > RCU-protected iteration, changing which slave is "last" mid-loop. > This causes the original skb to be double-consumed (double-freed). > > Replace the racy bond_is_last_slave() check with a simple index > comparison (i + 1 == slaves_count) against the pre-snapshot slave > count taken via READ_ONCE() before the loop. This preserves the > zero-copy optimization for the last slave while making the "last" > determination stable against concurrent list mutations. > > The UAF can trigger the following crash: > > ================================================================== > BUG: KASAN: slab-use-after-free in skb_clone > Read of size 8 at addr ffff888100ef8d40 by task exploit/147 > > CPU: 1 UID: 0 PID: 147 Comm: exploit Not tainted 7.0.0-rc3+ #4 PREEMPTLAZY > Call Trace: > > dump_stack_lvl (lib/dump_stack.c:123) > print_report (mm/kasan/report.c:379 mm/kasan/report.c:482) > kasan_report (mm/kasan/report.c:597) > skb_clone (include/linux/skbuff.h:1724 include/linux/skbuff.h:1792 include/linux/skbuff.h:3396 net/core/skbuff.c:2108) > bond_xmit_broadcast (drivers/net/bonding/bond_main.c:5334) > bond_start_xmit (drivers/net/bonding/bond_main.c:5567 drivers/net/bonding/bond_main.c:5593) > dev_hard_start_xmit (include/linux/netdevice.h:5325 include/linux/netdevice.h:5334 net/core/dev.c:3871 net/core/dev.c:3887) > __dev_queue_xmit (include/linux/netdevice.h:3601 net/core/dev.c:4838) > ip6_finish_output2 (include/net/neighbour.h:540 include/net/neighbour.h:554 net/ipv6/ip6_output.c:136) > ip6_finish_output (net/ipv6/ip6_output.c:208 net/ipv6/ip6_output.c:219) > ip6_output (net/ipv6/ip6_output.c:250) > ip6_send_skb (net/ipv6/ip6_output.c:1985) > udp_v6_send_skb (net/ipv6/udp.c:1442) > udpv6_sendmsg (net/ipv6/udp.c:1733) > __sys_sendto (net/socket.c:730 net/socket.c:742 net/socket.c:2206) > __x64_sys_sendto (net/socket.c:2209) > do_syscall_64 (arch/x86/entry/syscall_64.c:63 arch/x86/entry/syscall_64.c:94) > entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) > > > Allocated by task 147: > > Freed by task 147: > > The buggy address belongs to the object at ffff888100ef8c80 > which belongs to the cache skbuff_head_cache of size 224 > The buggy address is located 192 bytes inside of > freed 224-byte region [ffff888100ef8c80, ffff888100ef8d60) > > Memory state around the buggy address: > ffff888100ef8c00: fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc > ffff888100ef8c80: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > >ffff888100ef8d00: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc > ^ > ffff888100ef8d80: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb > ffff888100ef8e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ================================================================== > > Fixes: 4e5bd03ae346 ("net: bonding: fix bond_xmit_broadcast return value error bug") > Reported-by: Weiming Shi > Signed-off-by: Xiang Mei > Link: https://patch.msgid.link/20260326075553.3960562-1-xmei5@asu.edu > Signed-off-by: Paolo Abeni > Signed-off-by: Sasha Levin > Signed-off-by: Kevin Berry > Signed-off-by: Greg Kroah-Hartman > --- > drivers/net/bonding/bond_main.c | 12 ++++++++---- > 1 file changed, 8 insertions(+), 4 deletions(-) > > diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c > index 114ebaa284da..6484ba1ab14c 100644 > --- a/drivers/net/bonding/bond_main.c > +++ b/drivers/net/bonding/bond_main.c > @@ -5280,18 +5280,22 @@ static netdev_tx_t bond_xmit_broadcast(struct sk_buff *skb, > struct net_device *bond_dev) > { > struct bonding *bond = netdev_priv(bond_dev); > - struct slave *slave = NULL; > - struct list_head *iter; > + struct bond_up_slave *slaves; > bool xmit_suc = false; > bool skb_used = false; > + int slaves_count, i; > > - bond_for_each_slave_rcu(bond, slave, iter) { > + slaves = rcu_dereference(bond->all_slaves); > + > + slaves_count = slaves ? READ_ONCE(slaves->count) : 0; > + for (i = 0; i < slaves_count; i++) { > + struct slave *slave = slaves->arr[i]; > struct sk_buff *skb2; > > if (!(bond_slave_is_up(slave) && slave->link == BOND_LINK_UP)) > continue; > > - if (bond_is_last_slave(bond, slave)) { > + if (i + 1 == slaves_count) { > skb2 = skb; > skb_used = true; > } else { > > base-commit: 258cf62a6dfde3c6a39d120a56a298f2ed6a8901 > -- > 2.54.0.563.g4f69b47b94-goog > > Does not apply at all :(