Nikolay Aleksandrov
2019-Jan-27 21:34 UTC
[Bridge] KASAN: use-after-free Read in br_mdb_ip_get
On 27/01/2019 22:26, syzbot wrote:> 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 at 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]> > 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..> ?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 fc >> 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 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.
On Sun, Jan 27, 2019 at 10:34 PM Nikolay Aleksandrov <nikolay at cumulusnetworks.com> wrote:> > On 27/01/2019 22:26, syzbot wrote: > > 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 at 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] > > > >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:486 > > > Weird, 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.> > 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 fc > >> 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 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. > > -- >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 at 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.