Re: KASAN: use-after-free Read in br_mdb_ip_get
From: Dmitry Vyukov <dvyukov@google.com>
Date: 2019-01-28 08:28:51
Also in:
bridge, lkml
On Sun, Jan 27, 2019 at 10:34 PM Nikolay Aleksandrov [off-list ref] wrote:
On 27/01/2019 22:26, syzbot wrote:quoted
Hello, syzbot found the following crash on: HEAD commit: ba6069759381 Merge tag 'mmc-v5.0-rc2' of git://git.kernel... git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=17b342c4c00000 kernel config: https://syzkaller.appspot.com/x/.config?x=505743eba4e4f68 dashboard link: https://syzkaller.appspot.com/bug?extid=bc5ab0af2dbf3b0ae897 compiler: gcc (GCC) 9.0.0 20181231 (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+bc5ab0af2dbf3b0ae897@syzkaller.appspotmail.com bridge0: port 2(bridge_slave_1) entered blocking state bridge0: port 2(bridge_slave_1) entered forwarding state bridge0: port 1(bridge_slave_0) entered blocking state bridge0: port 1(bridge_slave_0) entered forwarding state ================================================================== BUG: KASAN: use-after-free in memcmp+0xb3/0xc0 lib/string.c:862 Read of size 1 at addr ffff88809f1efe70 by task syz-executor1/8111[snip]quoted
Allocated by task 8111: save_stack+0x45/0xd0 mm/kasan/common.c:73 set_track mm/kasan/common.c:85 [inline] __kasan_kmalloc mm/kasan/common.c:496 [inline] __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:469 kasan_kmalloc+0x9/0x10 mm/kasan/common.c:504 kmem_cache_alloc_trace+0x151/0x760 mm/slab.c:3609 kmalloc include/linux/slab.h:545 [inline] kzalloc include/linux/slab.h:740 [inline] br_multicast_new_group.part.0+0xdc/0x1a40 net/bridge/br_multicast.c:476 br_multicast_new_group+0x19d/0x200 net/bridge/br_multicast.c:471 br_multicast_add_group+0x4ce/0x7d0 net/bridge/br_multicast.c:552 br_ip6_multicast_add_group net/bridge/br_multicast.c:626 [inline] br_ip6_multicast_mld2_report net/bridge/br_multicast.c:1043 [inline] br_multicast_ipv6_rcv net/bridge/br_multicast.c:1667 [inline] br_multicast_rcv+0x24aa/0x4270 net/bridge/br_multicast.c:1705 br_dev_xmit+0x7f4/0x1780 net/bridge/br_device.c:93 __netdev_start_xmit include/linux/netdevice.h:4382 [inline] netdev_start_xmit include/linux/netdevice.h:4391 [inline] xmit_one net/core/dev.c:3278 [inline] dev_hard_start_xmit+0x261/0xc70 net/core/dev.c:3294 __dev_queue_xmit+0x2f8a/0x3a60 net/core/dev.c:3864 dev_queue_xmit+0x18/0x20 net/core/dev.c:3897 neigh_resolve_output net/core/neighbour.c:1476 [inline] neigh_resolve_output+0x6a0/0xb30 net/core/neighbour.c:1456 neigh_output include/net/neighbour.h:508 [inline] ip6_finish_output2+0xc56/0x28e0 net/ipv6/ip6_output.c:120 ip6_finish_output+0x577/0xc30 net/ipv6/ip6_output.c:154 NF_HOOK_COND include/linux/netfilter.h:278 [inline] ip6_output+0x23c/0xa00 net/ipv6/ip6_output.c:171 dst_output include/net/dst.h:444 [inline] NF_HOOK include/linux/netfilter.h:289 [inline] NF_HOOK include/linux/netfilter.h:283 [inline] mld_sendpack+0xa44/0xfd0 net/ipv6/mcast.c:1683 mld_send_cr net/ipv6/mcast.c:1979 [inline] mld_ifc_timer_expire+0x449/0x8a0 net/ipv6/mcast.c:2478 call_timer_fn+0x254/0x900 kernel/time/timer.c:1325 expire_timers kernel/time/timer.c:1362 [inline] __run_timers+0x6fc/0xd50 kernel/time/timer.c:1681 run_timer_softirq+0x52/0xb0 kernel/time/timer.c:1694 __do_softirq+0x30b/0xb11 kernel/softirq.c:292 Freed by task 8111: save_stack+0x45/0xd0 mm/kasan/common.c:73 set_track mm/kasan/common.c:85 [inline] __kasan_slab_free+0x102/0x150 mm/kasan/common.c:458 kasan_slab_free+0xe/0x10 mm/kasan/common.c:466 __cache_free mm/slab.c:3487 [inline] kfree+0xcf/0x230 mm/slab.c:3806 br_multicast_new_group.part.0+0x1489/0x1a40 net/bridge/br_multicast.c:486Weird, this is the kfree() on the error path of br_multicast_new_group() when rhashtable_lookup_insert_fast() fails, which means the entry should not be linked in the rhashtable or the hlist. All other frees are via kfree_rcu. I'll keep looking..
Humm.... +rhashtable.c maintianers
The code in br_multicast_new_group is effectively:
mp = kzalloc(sizeof(*mp), GFP_ATOMIC);
err = rhashtable_lookup_insert_fast(&br->mdb_hash_tbl, &mp->rhnode,
br_mdb_rht_params);
if (err)
kfree(mp);
So it looks like rhashtable_lookup_insert_fast both returned an error
and left the new object linked in the table. Since it happened only
once, it may have something to do with concurrent resizing/shrinking.
quoted
br_multicast_new_group+0x19d/0x200 net/bridge/br_multicast.c:471 br_multicast_add_group+0x4ce/0x7d0 net/bridge/br_multicast.c:552 br_ip6_multicast_add_group net/bridge/br_multicast.c:626 [inline] br_ip6_multicast_mld2_report net/bridge/br_multicast.c:1043 [inline] br_multicast_ipv6_rcv net/bridge/br_multicast.c:1667 [inline] br_multicast_rcv+0x24aa/0x4270 net/bridge/br_multicast.c:1705 br_dev_xmit+0x7f4/0x1780 net/bridge/br_device.c:93 __netdev_start_xmit include/linux/netdevice.h:4382 [inline] netdev_start_xmit include/linux/netdevice.h:4391 [inline] xmit_one net/core/dev.c:3278 [inline] dev_hard_start_xmit+0x261/0xc70 net/core/dev.c:3294 __dev_queue_xmit+0x2f8a/0x3a60 net/core/dev.c:3864 dev_queue_xmit+0x18/0x20 net/core/dev.c:3897 neigh_resolve_output net/core/neighbour.c:1476 [inline] neigh_resolve_output+0x6a0/0xb30 net/core/neighbour.c:1456 neigh_output include/net/neighbour.h:508 [inline] ip6_finish_output2+0xc56/0x28e0 net/ipv6/ip6_output.c:120 ip6_finish_output+0x577/0xc30 net/ipv6/ip6_output.c:154 NF_HOOK_COND include/linux/netfilter.h:278 [inline] ip6_output+0x23c/0xa00 net/ipv6/ip6_output.c:171 dst_output include/net/dst.h:444 [inline] NF_HOOK include/linux/netfilter.h:289 [inline] NF_HOOK include/linux/netfilter.h:283 [inline] mld_sendpack+0xa44/0xfd0 net/ipv6/mcast.c:1683 mld_send_cr net/ipv6/mcast.c:1979 [inline] mld_ifc_timer_expire+0x449/0x8a0 net/ipv6/mcast.c:2478 call_timer_fn+0x254/0x900 kernel/time/timer.c:1325 expire_timers kernel/time/timer.c:1362 [inline] __run_timers+0x6fc/0xd50 kernel/time/timer.c:1681 run_timer_softirq+0x52/0xb0 kernel/time/timer.c:1694 __do_softirq+0x30b/0xb11 kernel/softirq.c:292 The buggy address belongs to the object at ffff88809f1efe00 which belongs to the cache kmalloc-192 of size 192 The buggy address is located 112 bytes inside of 192-byte region [ffff88809f1efe00,ffff88809f1efec0) The buggy address belongs to the page: page:ffffea00027c7bc0 count:1 mapcount:0 mapping:ffff88812c3f0040 index:0x0 flags: 0x1fffc0000000200(slab) raw: 01fffc0000000200 ffffea00027df108 ffffea00027c7c48 ffff88812c3f0040 raw: 0000000000000000 ffff88809f1ef000 0000000100000010 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff88809f1efd00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff88809f1efd80: 00 00 fc fc fc fc fc fc fc fc fc fc fc fc fc fcquoted
ffff88809f1efe00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb^ ffff88809f1efe80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc ffff88809f1eff00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ================================================================== --- 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@googlegroups.com. syzbot will keep track of this bug report. See: https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with syzbot.-- You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group. To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bugs+unsubscribe@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/3c44c1ff-2790-ec06-35c6-3572b92170c7%40cumulusnetworks.com. For more options, visit https://groups.google.com/d/optout.