KASAN: use-after-free Read in mld_in_v1_mode

Status: fixed on 2020/04/15 17:19
Subsystems: net
[Documentation on labels]
Fix commit: e08ad80551b4 net-backports: net: add strict checks in netdev_name_node_alt_destroy()
First crash: 1617d, last: 1614d
Cause bisection: introduced by (bisect log) :
commit 36fbf1e52bd3ff8a5cb604955eedfc9350c2e6cc
Author: Jiri Pirko <>
Date: Mon Sep 30 09:48:16 2019 +0000

  net: rtnetlink: add linkprop commands to add and delete alternative ifnames

Crash: KASAN: use-after-free Read in l3mdev_master_ifindex_rcu (log)
Repro: C syz .config
Discussions (6)
Title Replies (including bot) Last reply
[patch 001/127] kcov: cleanup debug messages 1 (1) 2020/06/04 23:45
[PATCH v4 0/7] kcov: collect coverage from usb soft interrupts 16 (16) 2020/06/04 13:46
[patch 151/166] kcov: cleanup debug messages 1 (1) 2020/04/07 03:12
[PATCH v3 0/7] kcov: collect coverage from usb soft interrupts 8 (8) 2020/03/19 22:11
[PATCH v2 0/3] kcov: collect coverage from usb soft interrupts 6 (6) 2020/03/13 14:56
[PATCH v1 0/3] kcov: collect coverage from usb soft interrupts 6 (6) 2020/02/27 15:44

Sample crash report:
BUG: KASAN: use-after-free in dev_net include/linux/netdevice.h:2220 [inline]
BUG: KASAN: use-after-free in mld_force_mld_version net/ipv6/mcast.c:1172 [inline]
BUG: KASAN: use-after-free in mld_in_v2_mode_only net/ipv6/mcast.c:1180 [inline]
BUG: KASAN: use-after-free in mld_in_v1_mode+0x203/0x230 net/ipv6/mcast.c:1190
Read of size 8 at addr ffff88809c3a0588 by task swapper/1/0

CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.6.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x197/0x210 lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374
 __kasan_report.cold+0x1b/0x32 mm/kasan/report.c:506
 kasan_report+0x12/0x20 mm/kasan/common.c:641
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:135
 dev_net include/linux/netdevice.h:2220 [inline]
 mld_force_mld_version net/ipv6/mcast.c:1172 [inline]
 mld_in_v2_mode_only net/ipv6/mcast.c:1180 [inline]
 mld_in_v1_mode+0x203/0x230 net/ipv6/mcast.c:1190
 mld_send_initial_cr net/ipv6/mcast.c:2083 [inline]
 mld_dad_timer_expire+0x24/0x230 net/ipv6/mcast.c:2118
 call_timer_fn+0x1ac/0x780 kernel/time/timer.c:1404
 expire_timers kernel/time/timer.c:1449 [inline]
 __run_timers kernel/time/timer.c:1773 [inline]
 __run_timers kernel/time/timer.c:1740 [inline]
 run_timer_softirq+0x6c3/0x1790 kernel/time/timer.c:1786
 __do_softirq+0x262/0x98c kernel/softirq.c:292
 invoke_softirq kernel/softirq.c:373 [inline]
 irq_exit+0x19b/0x1e0 kernel/softirq.c:413
 exiting_irq arch/x86/include/asm/apic.h:546 [inline]
 smp_apic_timer_interrupt+0x1a3/0x610 arch/x86/kernel/apic/apic.c:1146
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829
RIP: 0010:native_safe_halt+0xe/0x10 arch/x86/include/asm/irqflags.h:61
Code: 08 f2 c4 f9 eb 8a cc cc cc cc cc cc e9 07 00 00 00 0f 00 2d 04 3a 59 00 f4 c3 66 90 e9 07 00 00 00 0f 00 2d f4 39 59 00 fb f4 <c3> cc 55 48 89 e5 41 57 41 56 41 55 41 54 53 e8 7e a9 73 f9 e8 19
RSP: 0018:ffffc90000d3fd68 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff13
RAX: 1ffffffff136761a RBX: ffff8880a99fc340 RCX: 0000000000000000
RDX: dffffc0000000000 RSI: 0000000000000006 RDI: ffff8880a99fcbd4
RBP: ffffc90000d3fd98 R08: ffff8880a99fc340 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: dffffc0000000000
R13: ffffffff8aa5a680 R14: 0000000000000000 R15: 0000000000000001
 arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:686
 default_idle_call+0x84/0xb0 kernel/sched/idle.c:94
 cpuidle_idle_call kernel/sched/idle.c:154 [inline]
 do_idle+0x3c8/0x6e0 kernel/sched/idle.c:269
 cpu_startup_entry+0x1b/0x20 kernel/sched/idle.c:361
 start_secondary+0x2f4/0x410 arch/x86/kernel/smpboot.c:264
 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:242

Allocated by task 9906:
 save_stack+0x23/0x90 mm/kasan/common.c:72
 set_track mm/kasan/common.c:80 [inline]
 __kasan_kmalloc mm/kasan/common.c:515 [inline]
 __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:488
 kasan_kmalloc+0x9/0x10 mm/kasan/common.c:529
 __do_kmalloc_node mm/slab.c:3616 [inline]
 __kmalloc_node+0x4e/0x70 mm/slab.c:3623
 kmalloc_node include/linux/slab.h:578 [inline]
 kvmalloc_node+0x68/0x100 mm/util.c:574
 kvmalloc include/linux/mm.h:645 [inline]
 kvzalloc include/linux/mm.h:653 [inline]
 alloc_netdev_mqs+0x98/0xe40 net/core/dev.c:9797
 vti6_init_net+0x244/0x810 net/ipv6/ip6_vti.c:1119
 ops_init+0xb3/0x420 net/core/net_namespace.c:137
 setup_net+0x2d5/0x8b0 net/core/net_namespace.c:327
 copy_net_ns+0x29e/0x5a0 net/core/net_namespace.c:468
 create_new_namespaces+0x403/0xb50 kernel/nsproxy.c:108
 unshare_nsproxy_namespaces+0xc2/0x200 kernel/nsproxy.c:229
 ksys_unshare+0x444/0x980 kernel/fork.c:2955
 __do_sys_unshare kernel/fork.c:3023 [inline]
 __se_sys_unshare kernel/fork.c:3021 [inline]
 __x64_sys_unshare+0x31/0x40 kernel/fork.c:3021
 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294

Freed by task 9906:
 save_stack+0x23/0x90 mm/kasan/common.c:72
 set_track mm/kasan/common.c:80 [inline]
 kasan_set_free_info mm/kasan/common.c:337 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/common.c:476
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:485
 __cache_free mm/slab.c:3426 [inline]
 kfree+0x10a/0x2c0 mm/slab.c:3757
 __netdev_name_node_alt_destroy+0x1ff/0x2a0 net/core/dev.c:322
 netdev_name_node_alt_destroy+0x57/0x80 net/core/dev.c:334
 rtnl_alt_ifname net/core/rtnetlink.c:3518 [inline]
 rtnl_linkprop.isra.0+0x575/0x6f0 net/core/rtnetlink.c:3567
 rtnl_dellinkprop+0x46/0x60 net/core/rtnetlink.c:3588
 rtnetlink_rcv_msg+0x45e/0xaf0 net/core/rtnetlink.c:5438
 netlink_rcv_skb+0x177/0x450 net/netlink/af_netlink.c:2477
 rtnetlink_rcv+0x1d/0x30 net/core/rtnetlink.c:5456
 netlink_unicast_kernel net/netlink/af_netlink.c:1302 [inline]
 netlink_unicast+0x59e/0x7e0 net/netlink/af_netlink.c:1328
 netlink_sendmsg+0x91c/0xea0 net/netlink/af_netlink.c:1917
 sock_sendmsg_nosec net/socket.c:652 [inline]
 sock_sendmsg+0xd7/0x130 net/socket.c:672
 ____sys_sendmsg+0x753/0x880 net/socket.c:2343
 ___sys_sendmsg+0x100/0x170 net/socket.c:2397
 __sys_sendmsg+0x105/0x1d0 net/socket.c:2430
 __do_sys_sendmsg net/socket.c:2439 [inline]
 __se_sys_sendmsg net/socket.c:2437 [inline]
 __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2437
 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294

The buggy address belongs to the object at ffff88809c3a0000
 which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 1416 bytes inside of
 4096-byte region [ffff88809c3a0000, ffff88809c3a1000)
The buggy address belongs to the page:
page:ffffea000270e800 refcount:1 mapcount:0 mapping:ffff8880aa402000 index:0x0 compound_mapcount: 0
flags: 0xfffe0000010200(slab|head)
raw: 00fffe0000010200 ffffea00027d5808 ffffea0002a48188 ffff8880aa402000
raw: 0000000000000000 ffff88809c3a0000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88809c3a0480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88809c3a0500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88809c3a0580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88809c3a0600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88809c3a0680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2020/02/17 01:08 upstream 11a48a5a18c6 1f448cd6 .config console log report syz C ci-upstream-kasan-gce
2020/02/15 23:35 upstream 829e69446995 5d7b90f1 .config console log report syz C ci-upstream-kasan-gce-386
2020/02/14 03:25 upstream 0bf999f9c5e7 c5ed587f .config console log report syz C ci-upstream-kasan-gce-386
* Struck through repros no longer work on HEAD.