From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 EA76335A3B6 for ; Mon, 13 Apr 2026 11:51:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776081075; cv=none; b=E9CZQiNCn7A4IwctI2TYTNut2boBQ571GjYfxln0tvuuIVYI02Q5Xe+qVzvcjoV46fWrWi0AsEfynXMcUKw21SC4tbQgWQdxxw7IRl9fAeNzSL+QOaAs6JOzAHpfbiE7qyRC+RHk+M4xlAyl9M5SMnYGPbx15Tb4F/U/Eo425p0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776081075; c=relaxed/simple; bh=RxSraddUffyU9jQA6QtBHxd6Xa+dQTKP5DaSnWRl7B4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=h5aBZ/TO3lhhtLe2eBYpIvDiLO0m5Hk0hsZYCYsGsc+/rKzVxZ4IAePyvdnpLGotnYx9oKB2iNZWrwqIR88+B58U71PH0SxpXZtHgFQDAdOJmlJCbYx66UjyjRdAHJkr1wQ67aAeLx3BvTpfEmjzgBoSZr9Ib9boXBm12HHV3N4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=p3IP8+BU; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="p3IP8+BU" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 23515C116C6; Mon, 13 Apr 2026 11:51:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1776081074; bh=RxSraddUffyU9jQA6QtBHxd6Xa+dQTKP5DaSnWRl7B4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=p3IP8+BU2IMkcqFZ0T0sVeIvJy3TfXD0gY6HfgthWLSmub6HI4Av2rmsyZqNuPjlQ h3AVjcUaRkNIB7ma37xmi3eanPFgOE/J7GHouG2Jzi0Vj9pa0d+dLHYF6KwVYXcRtk j+cjr9uRyIY6heJzi9WgpgPhrewBo+MMywYF34T0= Date: Mon, 13 Apr 2026 13:51:12 +0200 From: Greg KH To: Chenglong Tang Cc: stable@vger.kernel.org, xmei5@asu.edu, pabeni@redhat.com, sashal@kernel.org, Kevin Berry , Lee Jones Subject: Re: [PATCH 6.12.y] net: bonding: fix use-after-free in bond_xmit_broadcast() Message-ID: <2026041300-devotee-glowworm-db70@gregkh> References: 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: On Fri, Apr 10, 2026 at 02:09:42PM -0700, Chenglong Tang wrote: > 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 > Signed-off-by: Paolo Abeni > [Kevin Berry : fixed merge conflicts and adapted > to 6.12 struct] > Signed-off-by: Chenglong Tang > > diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c > index 2ac455a9d1bb..fb8d7fec27ee 100644 > --- a/drivers/net/bonding/bond_main.c > +++ b/drivers/net/bonding/bond_main.c > @@ -5346,23 +5346,33 @@ static netdev_tx_t bond_3ad_xor_xmit(struct > sk_buff *skb, > return bond_tx_drop(dev, skb); > } > -/* in broadcast mode, we send everything to all usable interfaces. */ > +/* in broadcast mode, we send everything to all or usable slave interfaces. > + * under rcu_read_lock when this function is called. > + */ This is totally corrupted and can not be applied :(