Hello, syzbot found the following crash on: HEAD commit: e12e00e388de Merge tag 'kbuild-fixes-v4.20' of git://git.k.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=14cdb6f5400000 kernel config: https://syzkaller.appspot.com/x/.config?x=8f215f21f041a0d7 dashboard link: https://syzkaller.appspot.com/bug?extid=04681da557a0e49a52e5 compiler: gcc (GCC) 8.0.1 20180413 (experimental) Unfortunately, I don't have any reproducer for this crash yet. IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+04681da557a0e49a52e5 at syzkaller.appspotmail.com device bridge_slave_1 left promiscuous mode bridge0: port 2(bridge_slave_1) entered disabled state device bridge_slave_0 left promiscuous mode bridge0: port 1(bridge_slave_0) entered disabled state =================================================================BUG: KASAN: use-after-free in nbp_vlan_rcu_free+0x152/0x160 net/bridge/br_vlan.c:200 Read of size 8 at addr ffff8881bbc44a18 by task swapper/1/0 CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.20.0-rc1+ #332 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: <IRQ> __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x244/0x39d lib/dump_stack.c:113 print_address_description.cold.7+0x9/0x1ff mm/kasan/report.c:256 kasan_report_error mm/kasan/report.c:354 [inline] kasan_report.cold.8+0x242/0x309 mm/kasan/report.c:412 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433 nbp_vlan_rcu_free+0x152/0x160 net/bridge/br_vlan.c:200 __rcu_reclaim kernel/rcu/rcu.h:240 [inline] rcu_do_batch kernel/rcu/tree.c:2437 [inline] invoke_rcu_callbacks kernel/rcu/tree.c:2716 [inline] rcu_process_callbacks+0x100a/0x1ac0 kernel/rcu/tree.c:2697 __do_softirq+0x308/0xb7e kernel/softirq.c:292 invoke_softirq kernel/softirq.c:373 [inline] irq_exit+0x17f/0x1c0 kernel/softirq.c:413 exiting_irq arch/x86/include/asm/apic.h:536 [inline] smp_apic_timer_interrupt+0x1cb/0x760 arch/x86/kernel/apic/apic.c:1061 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:804 </IRQ> RIP: 0010:native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:57 Code: e9 2c ff ff ff 48 89 c7 48 89 45 d8 e8 d3 43 f3 f9 48 8b 45 d8 e9 ca fe ff ff 48 89 df e8 c2 43 f3 f9 eb 82 55 48 89 e5 fb f4 <5d> c3 0f 1f 84 00 00 00 00 00 55 48 89 e5 f4 5d c3 90 90 90 90 90 RSP: 0018:ffff8881d9b27cb8 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff13 RAX: dffffc0000000000 RBX: 1ffff1103b364f9b RCX: 0000000000000000 RDX: 1ffffffff12a3f71 RSI: 0000000000000001 RDI: ffffffff8951fb88 RBP: ffff8881d9b27cb8 R08: ffff8881d9b14340 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffff8881d9b27d78 R13: ffffffff8a14e1e0 R14: 0000000000000000 R15: 0000000000000001 arch_safe_halt arch/x86/include/asm/paravirt.h:151 [inline] default_idle+0xbf/0x490 arch/x86/kernel/process.c:498 arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:489 default_idle_call+0x6d/0x90 kernel/sched/idle.c:93 cpuidle_idle_call kernel/sched/idle.c:153 [inline] do_idle+0x49b/0x5c0 kernel/sched/idle.c:262 cpu_startup_entry+0x18/0x20 kernel/sched/idle.c:353 start_secondary+0x487/0x5f0 arch/x86/kernel/smpboot.c:271 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243 Allocated by task 13858: save_stack+0x43/0xd0 mm/kasan/kasan.c:448 set_track mm/kasan/kasan.c:460 [inline] kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553 kmem_cache_alloc_trace+0x152/0x750 mm/slab.c:3620 kmalloc include/linux/slab.h:546 [inline] kzalloc include/linux/slab.h:741 [inline] br_vlan_add+0x6e5/0x1340 net/bridge/br_vlan.c:650 br_vlan_init+0x339/0x3e0 net/bridge/br_vlan.c:1047 br_dev_init+0x10d/0x2a0 net/bridge/br_device.c:134 register_netdevice+0x332/0x11d0 net/core/dev.c:8459 br_dev_newlink+0x2a/0x130 net/bridge/br_netlink.c:1309 rtnl_newlink+0xf08/0x1da0 net/core/rtnetlink.c:3175 rtnetlink_rcv_msg+0x46a/0xc20 net/core/rtnetlink.c:4947 netlink_rcv_skb+0x172/0x440 net/netlink/af_netlink.c:2477 rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:4965 netlink_unicast_kernel net/netlink/af_netlink.c:1310 [inline] netlink_unicast+0x5a5/0x760 net/netlink/af_netlink.c:1336 netlink_sendmsg+0xa18/0xfc0 net/netlink/af_netlink.c:1917 sock_sendmsg_nosec net/socket.c:621 [inline] sock_sendmsg+0xd5/0x120 net/socket.c:631 ___sys_sendmsg+0x7fd/0x930 net/socket.c:2116 __sys_sendmsg+0x11d/0x280 net/socket.c:2154 __do_sys_sendmsg net/socket.c:2163 [inline] __se_sys_sendmsg net/socket.c:2161 [inline] __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2161 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe Freed by task 9: save_stack+0x43/0xd0 mm/kasan/kasan.c:448 set_track mm/kasan/kasan.c:460 [inline] __kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528 __cache_free mm/slab.c:3498 [inline] kfree+0xcf/0x230 mm/slab.c:3817 br_master_vlan_rcu_free+0xa8/0xe0 net/bridge/br_vlan.c:174 __rcu_reclaim kernel/rcu/rcu.h:240 [inline] rcu_do_batch kernel/rcu/tree.c:2437 [inline] invoke_rcu_callbacks kernel/rcu/tree.c:2716 [inline] rcu_process_callbacks+0x100a/0x1ac0 kernel/rcu/tree.c:2697 __do_softirq+0x308/0xb7e kernel/softirq.c:292 The buggy address belongs to the object at ffff8881bbc44a00 which belongs to the cache kmalloc-96 of size 96 The buggy address is located 24 bytes inside of 96-byte region [ffff8881bbc44a00, ffff8881bbc44a60) The buggy address belongs to the page: page:ffffea0006ef1100 count:1 mapcount:0 mapping:ffff8881da8004c0 index:0x0 flags: 0x2fffc0000000200(slab) raw: 02fffc0000000200 ffffea0007471a08 ffffea000757b908 ffff8881da8004c0 raw: 0000000000000000 ffff8881bbc44000 0000000100000020 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8881bbc44900: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc ffff8881bbc44980: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc> ffff8881bbc44a00: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc^ ffff8881bbc44a80: 00 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc ffff8881bbc44b00: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc ================================================================= --- This bug is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller at googlegroups.com. syzbot will keep track of this bug report. See: https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with syzbot.
nikolay at cumulusnetworks.com
2018-Nov-12 08:32 UTC
[Bridge] KASAN: use-after-free Read in nbp_vlan_rcu_free
On 12 November 2018 06:51:02 CET, syzbot <syzbot+04681da557a0e49a52e5 at syzkaller.appspotmail.com> wrote:>Hello, > >syzbot found the following crash on: > >HEAD commit: e12e00e388de Merge tag 'kbuild-fixes-v4.20' of >git://git.k.. >git tree: upstream >console output: >https://syzkaller.appspot.com/x/log.txt?x=14cdb6f5400000 >kernel config: >https://syzkaller.appspot.com/x/.config?x=8f215f21f041a0d7 >dashboard link: >https://syzkaller.appspot.com/bug?extid=04681da557a0e49a52e5 >compiler: gcc (GCC) 8.0.1 20180413 (experimental) > >Unfortunately, I don't have any reproducer for this crash yet. > >IMPORTANT: if you fix the bug, please add the following tag to the >commit: >Reported-by: syzbot+04681da557a0e49a52e5 at syzkaller.appspotmail.comThanks, I'm about to fly out for LPC. Will take a look in a day.
Nikolay Aleksandrov
2018-Nov-13 01:01 UTC
[Bridge] [PATCH net] net: bridge: fix per-port vlan stats use-after-free on destruction
Syzbot reported a use-after-free of the global vlan context on port vlan
destruction. When I added per-port vlan stats I missed the fact that the
global vlan context can be freed before the per-port vlan rcu callback.
There're a few different ways to deal with this, I've chosen to add a
new private flag that is set only when per-port stats are allocated so
we can directly check it on destruction without dereferencing the global
context at all. The flag is internally controlled by the kernel and
user-space isn't allowed to set it.
Fixes: 9163a0fc1f0c ("net: bridge: add support for per-port vlan
stats")
Reported-by: syzbot+04681da557a0e49a52e5 at syzkaller.appspotmail.com
Signed-off-by: Nikolay Aleksandrov <nikolay at cumulusnetworks.com>
---
include/uapi/linux/if_bridge.h | 3 +++
net/bridge/br_netlink.c | 7 ++++++-
net/bridge/br_vlan.c | 3 ++-
3 files changed, 11 insertions(+), 2 deletions(-)
diff --git a/include/uapi/linux/if_bridge.h b/include/uapi/linux/if_bridge.h
index e41eda3c71f1..fa1f72276712 100644
--- a/include/uapi/linux/if_bridge.h
+++ b/include/uapi/linux/if_bridge.h
@@ -130,6 +130,9 @@ enum {
#define BRIDGE_VLAN_INFO_RANGE_BEGIN (1<<3) /* VLAN is start of vlan
range */
#define BRIDGE_VLAN_INFO_RANGE_END (1<<4) /* VLAN is end of vlan range */
#define BRIDGE_VLAN_INFO_BRENTRY (1<<5) /* Global bridge VLAN entry */
+#define BRIDGE_VLAN_INFO_PORT_STATS (1<<6) /* Per-port VLAN stats */
+
+#define BRIDGE_VLAN_INFO_PRIVATE_FLAGS BRIDGE_VLAN_INFO_PORT_STATS
struct bridge_vlan_info {
__u16 flags;
diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
index 3345f1984542..c600fedcfb76 100644
--- a/net/bridge/br_netlink.c
+++ b/net/bridge/br_netlink.c
@@ -527,8 +527,12 @@ int br_getlink(struct sk_buff *skb, u32 pid, u32 seq,
static int br_vlan_info(struct net_bridge *br, struct net_bridge_port *p,
int cmd, struct bridge_vlan_info *vinfo, bool *changed)
{
+ int err = -EINVAL;
bool curr_change;
- int err = 0;
+
+ /* don't allow user-space control over private flags */
+ if (vinfo->flags & BRIDGE_VLAN_INFO_PRIVATE_FLAGS)
+ return err;
switch (cmd) {
case RTM_SETLINK:
@@ -548,6 +552,7 @@ static int br_vlan_info(struct net_bridge *br, struct
net_bridge_port *p,
break;
case RTM_DELLINK:
+ err = 0;
if (p) {
if (!nbp_vlan_delete(p, vinfo->vid))
*changed = true;
diff --git a/net/bridge/br_vlan.c b/net/bridge/br_vlan.c
index 8c9297a01947..004e1f8c5040 100644
--- a/net/bridge/br_vlan.c
+++ b/net/bridge/br_vlan.c
@@ -197,7 +197,7 @@ static void nbp_vlan_rcu_free(struct rcu_head *rcu)
v = container_of(rcu, struct net_bridge_vlan, rcu);
WARN_ON(br_vlan_is_master(v));
/* if we had per-port stats configured then free them here */
- if (v->brvlan->stats != v->stats)
+ if (v->flags & BRIDGE_VLAN_INFO_PORT_STATS)
free_percpu(v->stats);
v->stats = NULL;
kfree(v);
@@ -264,6 +264,7 @@ static int __vlan_add(struct net_bridge_vlan *v, u16 flags)
err = -ENOMEM;
goto out_filt;
}
+ v->flags |= BRIDGE_VLAN_INFO_PORT_STATS;
} else {
v->stats = masterv->stats;
}
--
2.17.2