net/ipv4: use-after-free in ip_queue_xmit

[Andrey Konovalov]

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_select_ttl include/net/dst.h:176
[inline] at addr ffff88006ab3602c
BUG: KASAN: use-after-free in ip_queue_xmit+0x1817/0x1a30
net/ipv4/ip_output.c:485 at addr ffff88006ab3602c
Read of size 4 by task syz-executor1/12627
CPU: 3 PID: 12627 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_load4_noabort+0x14/0x20 mm/kasan/report.c:367
 ip_select_ttl include/net/dst.h:176 [inline]
 ip_queue_xmit+0x1817/0x1a30 net/ipv4/ip_output.c:485
 sctp_v4_xmit+0x10d/0x140 net/sctp/protocol.c:994
 sctp_packet_transmit+0x215c/0x3560 net/sctp/output.c:637
 sctp_outq_flush+0xade/0x3f90 net/sctp/outqueue.c:885
 sctp_outq_uncork+0x5a/0x70 net/sctp/outqueue.c:750
 sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1773 [inline]
 sctp_side_effects net/sctp/sm_sideeffect.c:1175 [inline]
 sctp_do_sm+0x5a0/0x6a50 net/sctp/sm_sideeffect.c:1147
 sctp_primitive_ASSOCIATE+0x9d/0xd0 net/sctp/primitive.c:88
 sctp_sendmsg+0x270d/0x3b50 net/sctp/socket.c:1954
 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:00007fdceca85b58 EFLAGS: 00000282 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 0000000000000016 RCX: 00000000004458d9
RDX: 0000000000000087 RSI: 0000000020003000 RDI: 0000000000000016
RBP: 00000000006e2fe0 R08: 0000000020003000 R09: 0000000000000010
R10: 0000000000040841 R11: 0000000000000282 R12: 00000000007080a8
R13: 000000000000000a R14: 0000000000000005 R15: 0000000000000084
Object at ffff88006ab36008, in cache kmalloc-64 size: 64
Allocated:
PID = 7243
 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]
 fib_create_info+0x8e0/0x3a30 net/ipv4/fib_semantics.c:1040
 fib_table_insert+0x1a5/0x1550 net/ipv4/fib_trie.c:1221
 ip_rt_ioctl+0xddc/0x1590 net/ipv4/fib_frontend.c:597
 inet_ioctl+0xf2/0x1c0 net/ipv4/af_inet.c:882
 sock_do_ioctl+0x65/0xb0 net/socket.c:906
 sock_ioctl+0x28f/0x440 net/socket.c:1004
 vfs_ioctl fs/ioctl.c:45 [inline]
 do_vfs_ioctl+0x1bf/0x1780 fs/ioctl.c:685
 SYSC_ioctl fs/ioctl.c:700 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:691
 entry_SYSCALL_64_fastpath+0x1f/0xc2
Freed:
PID = 12622
 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
 free_fib_info_rcu+0x4ba/0x5e0 net/ipv4/fib_semantics.c:218
 __rcu_reclaim kernel/rcu/rcu.h:118 [inline]
 rcu_do_batch.isra.64+0x947/0xcc0 kernel/rcu/tree.c:2879
 invoke_rcu_callbacks kernel/rcu/tree.c:3142 [inline]
 __rcu_process_callbacks kernel/rcu/tree.c:3109 [inline]
 rcu_process_callbacks+0x2cc/0xb90 kernel/rcu/tree.c:3126
 __do_softirq+0x2fb/0xb7d kernel/softirq.c:284
Memory state around the buggy address:
 ffff88006ab35f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88006ab35f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88006ab36000: fc fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc
                                  ^
 ffff88006ab36080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88006ab36100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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