Date:   Mon, 10 Apr 2017 16:33:20 +0200
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     "David S. Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        James Morris <jmorris@...ei.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Patrick McHardy <kaber@...sh.net>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     Eric Dumazet <edumazet@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Kostya Serebryany <kcc@...gle.com>,
        syzkaller <syzkaller@...glegroups.com>
Subject: net/ipv4: use-after-free in ip_check_mc_rcu

Hi,

I've got the following error report while fuzzing the kernel with syzkaller.

On commit 39da7c509acff13fc8cb12ec1bb20337c988ed36 (4.11-rc6).

Unfortunately it's not reproducible.

BUG: KASAN: use-after-free in ip_check_mc_rcu+0x805/0x8b0
net/ipv4/igmp.c:2645 at addr ffff880065b21cb8
Read of size 8 by task syz-executor1/2843
CPU: 3 PID: 2843 Comm: syz-executor1 Not tainted 4.11.0-rc6+ #206
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:16 [inline]
 dump_stack+0x292/0x398 lib/dump_stack.c:52
 kasan_object_err+0x1c/0x70 mm/kasan/report.c:164
 print_address_description mm/kasan/report.c:202 [inline]
 kasan_report_error mm/kasan/report.c:291 [inline]
 kasan_report+0x252/0x510 mm/kasan/report.c:347
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:368
 ip_check_mc_rcu+0x805/0x8b0 net/ipv4/igmp.c:2645
 __mkroute_output net/ipv4/route.c:2103 [inline]
 __ip_route_output_key_hash+0x241d/0x2ea0 net/ipv4/route.c:2375
 __ip_route_output_key include/net/route.h:122 [inline]
 ip_route_output_flow+0x29/0xa0 net/ipv4/route.c:2461
 udp_sendmsg+0x1565/0x2cd0 net/ipv4/udp.c:1015
 inet_sendmsg+0x164/0x5b0 net/ipv4/af_inet.c:762
 sock_sendmsg_nosec net/socket.c:633 [inline]
 sock_sendmsg+0xca/0x110 net/socket.c:643
 SYSC_sendto+0x660/0x810 net/socket.c:1696
 SyS_sendto+0x40/0x50 net/socket.c:1664
 entry_SYSCALL_64_fastpath+0x1f/0xc2
RIP: 0033:0x4458d9
RSP: 002b:00007f030b49bb58 EFLAGS: 00000282 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 00000000004458d9
RDX: 0000000000001000 RSI: 0000000020004000 RDI: 0000000000000005
RBP: 00000000006e2fc0 R08: 000000002000a000 R09: 0000000000000010
R10: 0000000000000000 R11: 0000000000000282 R12: 0000000000708000
R13: 0000000000000005 R14: 0000000020000ff3 R15: 0000000020006ffc
Object at ffff880065b21cb8, in cache kmalloc-64 size: 64
Allocated:
PID = 2841
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 save_stack+0x43/0xd0 mm/kasan/kasan.c:513
 set_track mm/kasan/kasan.c:525 [inline]
 kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:616
 kmem_cache_alloc_trace+0x82/0x270 mm/slub.c:2745
 kmalloc include/linux/slab.h:490 [inline]
 kzalloc include/linux/slab.h:663 [inline]
 ip_mc_add1_src net/ipv4/igmp.c:1909 [inline]
 ip_mc_add_src+0xbea/0x1020 net/ipv4/igmp.c:2033
 ip_mc_msfilter+0x5e5/0xcf0 net/ipv4/igmp.c:2403
 do_ip_setsockopt.isra.12+0x2a9f/0x36c0 net/ipv4/ip_sockglue.c:967
 ip_setsockopt+0x3a/0xb0 net/ipv4/ip_sockglue.c:1264
 raw_setsockopt+0xb7/0xd0 net/ipv4/raw.c:839
 sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2750
 SYSC_setsockopt net/socket.c:1798 [inline]
 SyS_setsockopt+0x270/0x3a0 net/socket.c:1777
 entry_SYSCALL_64_fastpath+0x1f/0xc2
Freed:
PID = 2841
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 save_stack+0x43/0xd0 mm/kasan/kasan.c:513
 set_track mm/kasan/kasan.c:525 [inline]
 kasan_slab_free+0x73/0xc0 mm/kasan/kasan.c:589
 slab_free_hook mm/slub.c:1357 [inline]
 slab_free_freelist_hook mm/slub.c:1379 [inline]
 slab_free mm/slub.c:2961 [inline]
 kfree+0xe8/0x2b0 mm/slub.c:3882
 ip_mc_del1_src+0x842/0x9d0 net/ipv4/igmp.c:1822
 ip_mc_del_src+0x59a/0xbe0 net/ipv4/igmp.c:1863
 ip_mc_leave_src+0x15d/0x320 net/ipv4/igmp.c:2155
 ip_mc_drop_socket+0x113/0x230 net/ipv4/igmp.c:2607
 inet_release+0x4e/0x1c0 net/ipv4/af_inet.c:411
 sock_release+0x8d/0x1e0 net/socket.c:597
 sock_close+0x16/0x20 net/socket.c:1072
 __fput+0x332/0x7f0 fs/file_table.c:209
 ____fput+0x15/0x20 fs/file_table.c:245
 task_work_run+0x19b/0x270 kernel/task_work.c:116
 exit_task_work include/linux/task_work.h:21 [inline]
 do_exit+0x18b6/0x2830 kernel/exit.c:878
 do_group_exit+0x149/0x420 kernel/exit.c:982
 get_signal+0x76d/0x17e0 kernel/signal.c:2318
 do_signal+0xd2/0x2190 arch/x86/kernel/signal.c:808
 exit_to_usermode_loop+0x170/0x200 arch/x86/entry/common.c:157
 prepare_exit_to_usermode arch/x86/entry/common.c:191 [inline]
 syscall_return_slowpath+0x3d3/0x420 arch/x86/entry/common.c:260
 entry_SYSCALL_64_fastpath+0xc0/0xc2
Memory state around the buggy address:
 ffff880065b21b80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff880065b21c00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff880065b21c80: fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb fc
                                        ^
 ffff880065b21d00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff880065b21d80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

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