* [PATCH v2] net: bonding: fix use-after-free in bond_xmit_broadcast() [not found] <20260428104138.reply-bonding-6.12@kernel.org> @ 2026-04-28 16:32 ` Kevin Berry 2026-04-28 22:41 ` Xiang Mei 0 siblings, 1 reply; 4+ messages in thread From: Kevin Berry @ 2026-04-28 16:32 UTC (permalink / raw) To: xmei5; +Cc: bestswngs, chenglongtang, joneslee, kpberry, pabeni, rnj, stable From: Xiang Mei <xmei5@asu.edu> 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: <TASK> 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) </TASK> 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 <bestswngs@gmail.com> Signed-off-by: Xiang Mei <xmei5@asu.edu> Link: https://patch.msgid.link/20260326075553.3960562-1-xmei5@asu.edu Signed-off-by: Kevin Berry <kpberry@google.com> --- drivers/net/bonding/bond_main.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c index 5035cfa74f1a..9f1a189d46f1 100644 --- a/drivers/net/bonding/bond_main.c +++ b/drivers/net/bonding/bond_main.c @@ -5326,14 +5326,21 @@ static netdev_tx_t bond_xmit_broadcast(struct sk_buff *skb, struct list_head *iter; bool xmit_suc = false; bool skb_used = false; + int slaves_count, i = 0; + slaves_count = READ_ONCE(bond->slave_cnt); bond_for_each_slave_rcu(bond, slave, iter) { struct sk_buff *skb2; + bool is_last; + + if (++i > slaves_count) + break; + is_last = (i == slaves_count); if (!(bond_slave_is_up(slave) && slave->link == BOND_LINK_UP)) continue; - if (bond_is_last_slave(bond, slave)) { + if (is_last) { skb2 = skb; skb_used = true; } else { base-commit: c286ea5e62389897291fa742d2bb909ecc9ef2d0 -- 2.54.0.545.g6539524ca2-goog ^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH v2] net: bonding: fix use-after-free in bond_xmit_broadcast() 2026-04-28 16:32 ` [PATCH v2] net: bonding: fix use-after-free in bond_xmit_broadcast() Kevin Berry @ 2026-04-28 22:41 ` Xiang Mei 2026-05-06 20:28 ` Kevin Berry 0 siblings, 1 reply; 4+ messages in thread From: Xiang Mei @ 2026-04-28 22:41 UTC (permalink / raw) To: Kevin Berry; +Cc: bestswngs, chenglongtang, joneslee, pabeni, rnj, stable Thanks Kevin for picking this up for 6.12.y. We can't backport the upstream patch since the upstream rewrite that introduced the bond_up_slave snapshot array isn't in this tree. Confirmed it fixes the double-free without introducing concerning side effects. Acked-by: Xiang Mei <xmei5@asu.edu> On Tue, Apr 28, 2026 at 9:32 AM Kevin Berry <kpberry@google.com> wrote: > > From: Xiang Mei <xmei5@asu.edu> > > 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: > <TASK> > 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) > </TASK> > > 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 <bestswngs@gmail.com> > Signed-off-by: Xiang Mei <xmei5@asu.edu> > Link: https://patch.msgid.link/20260326075553.3960562-1-xmei5@asu.edu > Signed-off-by: Kevin Berry <kpberry@google.com> > --- > drivers/net/bonding/bond_main.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c > index 5035cfa74f1a..9f1a189d46f1 100644 > --- a/drivers/net/bonding/bond_main.c > +++ b/drivers/net/bonding/bond_main.c > @@ -5326,14 +5326,21 @@ static netdev_tx_t bond_xmit_broadcast(struct sk_buff *skb, > struct list_head *iter; > bool xmit_suc = false; > bool skb_used = false; > + int slaves_count, i = 0; > > + slaves_count = READ_ONCE(bond->slave_cnt); > bond_for_each_slave_rcu(bond, slave, iter) { > struct sk_buff *skb2; > + bool is_last; > + > + if (++i > slaves_count) > + break; > + is_last = (i == slaves_count); > > if (!(bond_slave_is_up(slave) && slave->link == BOND_LINK_UP)) > continue; > > - if (bond_is_last_slave(bond, slave)) { > + if (is_last) { > skb2 = skb; > skb_used = true; > } else { > > base-commit: c286ea5e62389897291fa742d2bb909ecc9ef2d0 > -- > 2.54.0.545.g6539524ca2-goog > ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v2] net: bonding: fix use-after-free in bond_xmit_broadcast() 2026-04-28 22:41 ` Xiang Mei @ 2026-05-06 20:28 ` Kevin Berry 2026-05-06 20:28 ` [PATCH] " Kevin Berry 0 siblings, 1 reply; 4+ messages in thread From: Kevin Berry @ 2026-05-06 20:28 UTC (permalink / raw) To: xmei5; +Cc: bestswngs, chenglongtang, joneslee, kpberry, pabeni, rnj, stable Hi all, Sending the patch for 6.6 as well since it should be the same as the 6.12 patch. Tested by compiling. Thanks, Kevin ^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH] net: bonding: fix use-after-free in bond_xmit_broadcast() 2026-05-06 20:28 ` Kevin Berry @ 2026-05-06 20:28 ` Kevin Berry 0 siblings, 0 replies; 4+ messages in thread From: Kevin Berry @ 2026-05-06 20:28 UTC (permalink / raw) To: xmei5 Cc: bestswngs, chenglongtang, joneslee, kpberry, pabeni, rnj, stable, Sasha Levin, Greg Kroah-Hartman From: Xiang Mei <xmei5@asu.edu> 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: <TASK> 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) </TASK> 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 <bestswngs@gmail.com> Signed-off-by: Xiang Mei <xmei5@asu.edu> Link: https://patch.msgid.link/20260326075553.3960562-1-xmei5@asu.edu Signed-off-by: Paolo Abeni <pabeni@redhat.com> Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Kevin Berry <kpberry@google.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- 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 ^ permalink raw reply related [flat|nested] 4+ messages in thread
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[not found] <20260428104138.reply-bonding-6.12@kernel.org>
2026-04-28 16:32 ` [PATCH v2] net: bonding: fix use-after-free in bond_xmit_broadcast() Kevin Berry
2026-04-28 22:41 ` Xiang Mei
2026-05-06 20:28 ` Kevin Berry
2026-05-06 20:28 ` [PATCH] " Kevin Berry
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