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net/ipv4: use-after-free in add_grec

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  net/ipv4: use-after-free in add_grec Andrey Konovalov <andreyknvl@google.com> - 2017-05-31 11:50 +0200
    Re: net/ipv4: use-after-free in add_grec Eric Dumazet <eric.dumazet@gmail.com> - 2017-05-31 18:20 +0200
      Re: net/ipv4: use-after-free in add_grec Eric Dumazet <edumazet@google.com> - 2017-06-01 02:00 +0200
        Re: net/ipv4: use-after-free in add_grec Eric Dumazet <eric.dumazet@gmail.com> - 2017-06-01 02:20 +0200
          Re: net/ipv4: use-after-free in add_grec Andrey Konovalov <andreyknvl@google.com> - 2017-06-01 14:10 +0200
      Re: net/ipv4: use-after-free in add_grec Cong Wang <xiyou.wangcong@gmail.com> - 2017-06-01 02:00 +0200

#1654075 — net/ipv4: use-after-free in add_grec

Hi,

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

On commit 5ed02dbb497422bf225783f46e6eadd237d23d6b (4.12-rc3).

Unfortunately it's not reproducible.

==================================================================
BUG: KASAN: use-after-free in add_grec+0x101e/0x1090 net/ipv4/igmp.c:473
Read of size 8 at addr ffff88003053c1a0 by task swapper/0/0

CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.12.0-rc3+ #370
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:16 [inline]
 dump_stack+0x292/0x395 lib/dump_stack.c:52
 print_address_description+0x73/0x280 mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report+0x22b/0x340 mm/kasan/report.c:408
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:429
 add_grec+0x101e/0x1090 net/ipv4/igmp.c:473
 igmpv3_send_cr net/ipv4/igmp.c:663 [inline]
 igmp_ifc_timer_expire+0x46d/0xa80 net/ipv4/igmp.c:768
IPVS: length: 51 != 8
 call_timer_fn+0x23f/0x800 kernel/time/timer.c:1268
 expire_timers kernel/time/timer.c:1307 [inline]
 __run_timers+0x94e/0xcd0 kernel/time/timer.c:1601
 run_timer_softirq+0x21/0x80 kernel/time/timer.c:1614
 __do_softirq+0x2fb/0xb99 kernel/softirq.c:284
 invoke_softirq kernel/softirq.c:364 [inline]
 irq_exit+0x19e/0x1d0 kernel/softirq.c:405
 exiting_irq arch/x86/include/asm/apic.h:652 [inline]
 smp_apic_timer_interrupt+0x76/0xa0 arch/x86/kernel/apic/apic.c:966
 apic_timer_interrupt+0x93/0xa0 arch/x86/entry/entry_64.S:481
RIP: 0010:native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:53
RSP: 0018:ffffffff85a079a8 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff10
RAX: dffffc0000000020 RBX: 1ffffffff0b40f38 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffffff85a2a9e4
RBP: ffffffff85a079a8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: dffffc0000000000
R13: ffffffff85a07a60 R14: ffffffff86171338 R15: 1ffffffff0b40f5b
 </IRQ>
 arch_safe_halt arch/x86/include/asm/paravirt.h:98 [inline]
 default_idle+0x8f/0x440 arch/x86/kernel/process.c:341
 arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:332
 default_idle_call+0x36/0x60 kernel/sched/idle.c:98
 cpuidle_idle_call kernel/sched/idle.c:156 [inline]
 do_idle+0x348/0x420 kernel/sched/idle.c:245
 cpu_startup_entry+0x18/0x20 kernel/sched/idle.c:350
 rest_init+0x18d/0x1a0 init/main.c:415
 start_kernel+0x747/0x779 init/main.c:679
 x86_64_start_reservations+0x2a/0x2c arch/x86/kernel/head64.c:196
 x86_64_start_kernel+0x132/0x141 arch/x86/kernel/head64.c:177
 secondary_startup_64+0x9f/0x9f arch/x86/kernel/head_64.S:304

Allocated by task 30543:
 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:617
 kmem_cache_alloc_trace+0x82/0x270 mm/slub.c:2745
 kmalloc include/linux/slab.h:492 [inline]
 kzalloc include/linux/slab.h:665 [inline]
 ip_mc_add1_src net/ipv4/igmp.c:1909 [inline]
 ip_mc_add_src+0x6cd/0x1020 net/ipv4/igmp.c:2033
 ip_mc_msfilter+0x5e5/0xcf0 net/ipv4/igmp.c:2403
 do_ip_setsockopt.isra.12+0x2d47/0x38c0 net/ipv4/ip_sockglue.c:959
 ip_setsockopt+0x3a/0xb0 net/ipv4/ip_sockglue.c:1256
 tcp_setsockopt+0x82/0xd0 net/ipv4/tcp.c:2740
 sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2844
 SYSC_setsockopt net/socket.c:1798 [inline]
 SyS_setsockopt+0x270/0x3a0 net/socket.c:1777
 entry_SYSCALL_64_fastpath+0x1f/0xbe

Freed by task 30543:
 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+0x72/0xc0 mm/kasan/kasan.c:590
 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_clear_src+0x69/0x1c0 net/ipv4/igmp.c:2078
 ip_mc_dec_group+0x19a/0x470 net/ipv4/igmp.c:1618
 ip_mc_drop_socket+0x145/0x230 net/ipv4/igmp.c:2609
 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+0x18a3/0x2820 kernel/exit.c:878
 do_group_exit+0x149/0x420 kernel/exit.c:982
 get_signal+0x76d/0x1790 kernel/signal.c:2318
 do_signal+0xd2/0x2130 arch/x86/kernel/signal.c:808
 exit_to_usermode_loop+0x17a/0x210 arch/x86/entry/common.c:157
 prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline]
 syscall_return_slowpath+0x3ba/0x410 arch/x86/entry/common.c:263
 entry_SYSCALL_64_fastpath+0xbc/0xbe

The buggy address belongs to the object at ffff88003053c1a0
 which belongs to the cache kmalloc-64 of size 64
The buggy address is located 0 bytes inside of
 64-byte region [ffff88003053c1a0, ffff88003053c1e0)
The buggy address belongs to the page:
page:ffffea0000c14f00 count:1 mapcount:0 mapping:          (null)
index:0x0 compound_mapcount: 0
flags: 0x100000000008100(slab|head)
raw: 0100000000008100 0000000000000000 0000000000000000 0000000100140014
raw: ffffea0000c2f520 ffffea0000e20aa0 ffff88003e80f740 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88003053c080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88003053c100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88003053c180: fc fc fc fc fb fb fb fb fb fb fb fb fc fc fc fc
                               ^
 ffff88003053c200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88003053c280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

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#1654410

On Wed, 2017-05-31 at 11:46 +0200, Andrey Konovalov wrote:
> Hi,
> 
> I've got the following error report while fuzzing the kernel with syzkaller.
> 
> On commit 5ed02dbb497422bf225783f46e6eadd237d23d6b (4.12-rc3).
> 
> Unfortunately it's not reproducible.
> 
> ==================================================================
> BUG: KASAN: use-after-free in add_grec+0x101e/0x1090 net/ipv4/igmp.c:473
> Read of size 8 at addr ffff88003053c1a0 by task swapper/0/0
> 
> CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.12.0-rc3+ #370
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
> Call Trace:
>  <IRQ>
>  __dump_stack lib/dump_stack.c:16 [inline]
>  dump_stack+0x292/0x395 lib/dump_stack.c:52
>  print_address_description+0x73/0x280 mm/kasan/report.c:252
>  kasan_report_error mm/kasan/report.c:351 [inline]
>  kasan_report+0x22b/0x340 mm/kasan/report.c:408
>  __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:429
>  add_grec+0x101e/0x1090 net/ipv4/igmp.c:473
>  igmpv3_send_cr net/ipv4/igmp.c:663 [inline]
>  igmp_ifc_timer_expire+0x46d/0xa80 net/ipv4/igmp.c:768
> IPVS: length: 51 != 8
>  call_timer_fn+0x23f/0x800 kernel/time/timer.c:1268
>  expire_timers kernel/time/timer.c:1307 [inline]
>  __run_timers+0x94e/0xcd0 kernel/time/timer.c:1601
>  run_timer_softirq+0x21/0x80 kernel/time/timer.c:1614
>  __do_softirq+0x2fb/0xb99 kernel/softirq.c:284
>  invoke_softirq kernel/softirq.c:364 [inline]
>  irq_exit+0x19e/0x1d0 kernel/softirq.c:405
>  exiting_irq arch/x86/include/asm/apic.h:652 [inline]
>  smp_apic_timer_interrupt+0x76/0xa0 arch/x86/kernel/apic/apic.c:966
>  apic_timer_interrupt+0x93/0xa0 arch/x86/entry/entry_64.S:481
> RIP: 0010:native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:53
> RSP: 0018:ffffffff85a079a8 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff10
> RAX: dffffc0000000020 RBX: 1ffffffff0b40f38 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffffff85a2a9e4
> RBP: ffffffff85a079a8 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: dffffc0000000000
> R13: ffffffff85a07a60 R14: ffffffff86171338 R15: 1ffffffff0b40f5b
>  </IRQ>
>  arch_safe_halt arch/x86/include/asm/paravirt.h:98 [inline]
>  default_idle+0x8f/0x440 arch/x86/kernel/process.c:341
>  arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:332
>  default_idle_call+0x36/0x60 kernel/sched/idle.c:98
>  cpuidle_idle_call kernel/sched/idle.c:156 [inline]
>  do_idle+0x348/0x420 kernel/sched/idle.c:245
>  cpu_startup_entry+0x18/0x20 kernel/sched/idle.c:350
>  rest_init+0x18d/0x1a0 init/main.c:415
>  start_kernel+0x747/0x779 init/main.c:679
>  x86_64_start_reservations+0x2a/0x2c arch/x86/kernel/head64.c:196
>  x86_64_start_kernel+0x132/0x141 arch/x86/kernel/head64.c:177
>  secondary_startup_64+0x9f/0x9f arch/x86/kernel/head_64.S:304
> 
> Allocated by task 30543:
>  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:617
>  kmem_cache_alloc_trace+0x82/0x270 mm/slub.c:2745
>  kmalloc include/linux/slab.h:492 [inline]
>  kzalloc include/linux/slab.h:665 [inline]
>  ip_mc_add1_src net/ipv4/igmp.c:1909 [inline]
>  ip_mc_add_src+0x6cd/0x1020 net/ipv4/igmp.c:2033
>  ip_mc_msfilter+0x5e5/0xcf0 net/ipv4/igmp.c:2403
>  do_ip_setsockopt.isra.12+0x2d47/0x38c0 net/ipv4/ip_sockglue.c:959
>  ip_setsockopt+0x3a/0xb0 net/ipv4/ip_sockglue.c:1256
>  tcp_setsockopt+0x82/0xd0 net/ipv4/tcp.c:2740
>  sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2844
>  SYSC_setsockopt net/socket.c:1798 [inline]
>  SyS_setsockopt+0x270/0x3a0 net/socket.c:1777
>  entry_SYSCALL_64_fastpath+0x1f/0xbe
> 
> Freed by task 30543:
>  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+0x72/0xc0 mm/kasan/kasan.c:590
>  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_clear_src+0x69/0x1c0 net/ipv4/igmp.c:2078
>  ip_mc_dec_group+0x19a/0x470 net/ipv4/igmp.c:1618
>  ip_mc_drop_socket+0x145/0x230 net/ipv4/igmp.c:2609
>  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+0x18a3/0x2820 kernel/exit.c:878
>  do_group_exit+0x149/0x420 kernel/exit.c:982
>  get_signal+0x76d/0x1790 kernel/signal.c:2318
>  do_signal+0xd2/0x2130 arch/x86/kernel/signal.c:808
>  exit_to_usermode_loop+0x17a/0x210 arch/x86/entry/common.c:157
>  prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline]
>  syscall_return_slowpath+0x3ba/0x410 arch/x86/entry/common.c:263
>  entry_SYSCALL_64_fastpath+0xbc/0xbe
> 
> The buggy address belongs to the object at ffff88003053c1a0
>  which belongs to the cache kmalloc-64 of size 64
> The buggy address is located 0 bytes inside of
>  64-byte region [ffff88003053c1a0, ffff88003053c1e0)
> The buggy address belongs to the page:
> page:ffffea0000c14f00 count:1 mapcount:0 mapping:          (null)
> index:0x0 compound_mapcount: 0
> flags: 0x100000000008100(slab|head)
> raw: 0100000000008100 0000000000000000 0000000000000000 0000000100140014
> raw: ffffea0000c2f520 ffffea0000e20aa0 ffff88003e80f740 0000000000000000
> page dumped because: kasan: bad access detected
> 
> Memory state around the buggy address:
>  ffff88003053c080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>  ffff88003053c100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> >ffff88003053c180: fc fc fc fc fb fb fb fb fb fb fb fb fc fc fc fc
>                                ^
>  ffff88003053c200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>  ffff88003053c280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ==================================================================

I have the feeling that ip_mc_clear_src() is called too soon.

We should call it once all users have released their reference.

I am not sure we have to call it after the RCU grace period,
more analysis of the code is needed.


diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index 44fd86de2823dd17de16276a8ec01b190e69b8b4..f172d251c5f2cda8fc8bedd65fa16cdfe33a4d40 100644
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -174,6 +174,7 @@ static int ip_mc_add_src(struct in_device *in_dev, __be32 *pmca, int sfmode,
 static void ip_ma_put(struct ip_mc_list *im)
 {
 	if (atomic_dec_and_test(&im->refcnt)) {
+		ip_mc_clear_src(im);
 		in_dev_put(im->interface);
 		kfree_rcu(im, rcu);
 	}
@@ -1615,7 +1616,6 @@ void ip_mc_dec_group(struct in_device *in_dev, __be32 addr)
 				*ip = i->next_rcu;
 				in_dev->mc_count--;
 				igmp_group_dropped(i);
-				ip_mc_clear_src(i);
 
 				if (!in_dev->dead)
 					ip_rt_multicast_event(in_dev);

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#1654728

On Wed, May 31, 2017 at 4:49 PM, Cong Wang <xiyou.wangcong@gmail.com> wrote:
> On Wed, May 31, 2017 at 9:12 AM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
>> On Wed, 2017-05-31 at 11:46 +0200, Andrey Konovalov wrote:
>>> Hi,
>>>
>>> I've got the following error report while fuzzing the kernel with syzkaller.
>>>
>>> On commit 5ed02dbb497422bf225783f46e6eadd237d23d6b (4.12-rc3).
>>>
>>> Unfortunately it's not reproducible.
>>>
>>> ==================================================================
>>> BUG: KASAN: use-after-free in add_grec+0x101e/0x1090 net/ipv4/igmp.c:473
>>> Read of size 8 at addr ffff88003053c1a0 by task swapper/0/0
>>>
>>> CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.12.0-rc3+ #370
>>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
>>> Call Trace:
>>>  <IRQ>
>>>  __dump_stack lib/dump_stack.c:16 [inline]
>>>  dump_stack+0x292/0x395 lib/dump_stack.c:52
>>>  print_address_description+0x73/0x280 mm/kasan/report.c:252
>>>  kasan_report_error mm/kasan/report.c:351 [inline]
>>>  kasan_report+0x22b/0x340 mm/kasan/report.c:408
>>>  __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:429
>>>  add_grec+0x101e/0x1090 net/ipv4/igmp.c:473
>>>  igmpv3_send_cr net/ipv4/igmp.c:663 [inline]
>>>  igmp_ifc_timer_expire+0x46d/0xa80 net/ipv4/igmp.c:768
>>> IPVS: length: 51 != 8
>>>  call_timer_fn+0x23f/0x800 kernel/time/timer.c:1268
>>>  expire_timers kernel/time/timer.c:1307 [inline]
>>>  __run_timers+0x94e/0xcd0 kernel/time/timer.c:1601
>>>  run_timer_softirq+0x21/0x80 kernel/time/timer.c:1614
>>>  __do_softirq+0x2fb/0xb99 kernel/softirq.c:284
>>>  invoke_softirq kernel/softirq.c:364 [inline]
>>>  irq_exit+0x19e/0x1d0 kernel/softirq.c:405
>>>  exiting_irq arch/x86/include/asm/apic.h:652 [inline]
>>>  smp_apic_timer_interrupt+0x76/0xa0 arch/x86/kernel/apic/apic.c:966
>>>  apic_timer_interrupt+0x93/0xa0 arch/x86/entry/entry_64.S:481
>>> RIP: 0010:native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:53
>>> RSP: 0018:ffffffff85a079a8 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff10
>>> RAX: dffffc0000000020 RBX: 1ffffffff0b40f38 RCX: 0000000000000000
>>> RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffffff85a2a9e4
>>> RBP: ffffffff85a079a8 R08: 0000000000000000 R09: 0000000000000000
>>> R10: 0000000000000000 R11: 0000000000000000 R12: dffffc0000000000
>>> R13: ffffffff85a07a60 R14: ffffffff86171338 R15: 1ffffffff0b40f5b
>>>  </IRQ>
>>>  arch_safe_halt arch/x86/include/asm/paravirt.h:98 [inline]
>>>  default_idle+0x8f/0x440 arch/x86/kernel/process.c:341
>>>  arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:332
>>>  default_idle_call+0x36/0x60 kernel/sched/idle.c:98
>>>  cpuidle_idle_call kernel/sched/idle.c:156 [inline]
>>>  do_idle+0x348/0x420 kernel/sched/idle.c:245
>>>  cpu_startup_entry+0x18/0x20 kernel/sched/idle.c:350
>>>  rest_init+0x18d/0x1a0 init/main.c:415
>>>  start_kernel+0x747/0x779 init/main.c:679
>>>  x86_64_start_reservations+0x2a/0x2c arch/x86/kernel/head64.c:196
>>>  x86_64_start_kernel+0x132/0x141 arch/x86/kernel/head64.c:177
>>>  secondary_startup_64+0x9f/0x9f arch/x86/kernel/head_64.S:304
>>>
>>> Allocated by task 30543:
>>>  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:617
>>>  kmem_cache_alloc_trace+0x82/0x270 mm/slub.c:2745
>>>  kmalloc include/linux/slab.h:492 [inline]
>>>  kzalloc include/linux/slab.h:665 [inline]
>>>  ip_mc_add1_src net/ipv4/igmp.c:1909 [inline]
>>>  ip_mc_add_src+0x6cd/0x1020 net/ipv4/igmp.c:2033
>>>  ip_mc_msfilter+0x5e5/0xcf0 net/ipv4/igmp.c:2403
>>>  do_ip_setsockopt.isra.12+0x2d47/0x38c0 net/ipv4/ip_sockglue.c:959
>>>  ip_setsockopt+0x3a/0xb0 net/ipv4/ip_sockglue.c:1256
>>>  tcp_setsockopt+0x82/0xd0 net/ipv4/tcp.c:2740
>>>  sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2844
>>>  SYSC_setsockopt net/socket.c:1798 [inline]
>>>  SyS_setsockopt+0x270/0x3a0 net/socket.c:1777
>>>  entry_SYSCALL_64_fastpath+0x1f/0xbe
>>>
>>> Freed by task 30543:
>>>  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+0x72/0xc0 mm/kasan/kasan.c:590
>>>  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_clear_src+0x69/0x1c0 net/ipv4/igmp.c:2078
>>>  ip_mc_dec_group+0x19a/0x470 net/ipv4/igmp.c:1618
>>>  ip_mc_drop_socket+0x145/0x230 net/ipv4/igmp.c:2609
>>>  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+0x18a3/0x2820 kernel/exit.c:878
>>>  do_group_exit+0x149/0x420 kernel/exit.c:982
>>>  get_signal+0x76d/0x1790 kernel/signal.c:2318
>>>  do_signal+0xd2/0x2130 arch/x86/kernel/signal.c:808
>>>  exit_to_usermode_loop+0x17a/0x210 arch/x86/entry/common.c:157
>>>  prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline]
>>>  syscall_return_slowpath+0x3ba/0x410 arch/x86/entry/common.c:263
>>>  entry_SYSCALL_64_fastpath+0xbc/0xbe
>>>
>>> The buggy address belongs to the object at ffff88003053c1a0
>>>  which belongs to the cache kmalloc-64 of size 64
>>> The buggy address is located 0 bytes inside of
>>>  64-byte region [ffff88003053c1a0, ffff88003053c1e0)
>>> The buggy address belongs to the page:
>>> page:ffffea0000c14f00 count:1 mapcount:0 mapping:          (null)
>>> index:0x0 compound_mapcount: 0
>>> flags: 0x100000000008100(slab|head)
>>> raw: 0100000000008100 0000000000000000 0000000000000000 0000000100140014
>>> raw: ffffea0000c2f520 ffffea0000e20aa0 ffff88003e80f740 0000000000000000
>>> page dumped because: kasan: bad access detected
>>>
>>> Memory state around the buggy address:
>>>  ffff88003053c080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>>>  ffff88003053c100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>>> >ffff88003053c180: fc fc fc fc fb fb fb fb fb fb fb fb fc fc fc fc
>>>                                ^
>>>  ffff88003053c200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>>>  ffff88003053c280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>>> ==================================================================
>>
>> I have the feeling that ip_mc_clear_src() is called too soon.
>>
>> We should call it once all users have released their reference.
>
> In this case, ip_mc_clear_src() is called when the ->users hits
> zero, therefore I think we possibly miss the refcnt on ->users.
>
> diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
> index 44fd86d..c2f3347 100644
> --- a/net/ipv4/igmp.c
> +++ b/net/ipv4/igmp.c
> @@ -1886,6 +1886,7 @@ static int ip_mc_del_src(struct in_device
> *in_dev, __be32 *pmca, int sfmode,
>                 igmp_ifc_event(pmc->interface);
>  #endif
>         }
> +       pmc->users--;
>  out_unlock:
>         spin_unlock_bh(&pmc->lock);
>         return err;
> @@ -2025,6 +2026,7 @@ static int ip_mc_add_src(struct in_device
> *in_dev, __be32 *pmca, int sfmode,
>  #ifdef CONFIG_IP_MULTICAST
>         sf_markstate(pmc);
>  #endif
> +       pmc->users++;
>         isexclude = pmc->sfmode == MCAST_EXCLUDE;
>         if (!delta)
>                 pmc->sfcount[sfmode]++;


The issue here is the timer firing while ip_mc_clear_src() has been
already called.

My patch should fix the problem.

Or another one using del_timer_sync() instead of del_timer() in
igmp_stop_timer(), but such a change would be more invasive,
since the del_timer_sync() would need to happen while im->lock
spinlock is not held.

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#1654735

On Wed, 2017-05-31 at 16:55 -0700, Eric Dumazet wrote:

> The issue here is the timer firing while ip_mc_clear_src() has been
> already called.
> 
> My patch should fix the problem.
> 
> Or another one using del_timer_sync() instead of del_timer() in
> igmp_stop_timer(), but such a change would be more invasive,
> since the del_timer_sync() would need to happen while im->lock
> spinlock is not held.

BTW, I guess that Andrey could try to add a delay to trigger the bug
more often.

diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index 44fd86de2823dd17de16276a8ec01b190e69b8b4..84fff17daab0832c470a613b29b2aaade07cec0a 100644
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -798,7 +798,7 @@ static void igmp_timer_expire(unsigned long data)
 	}
 	im->reporter = 1;
 	spin_unlock(&im->lock);
-
+	udelay(10000);
 	if (IGMP_V1_SEEN(in_dev))
 		igmp_send_report(in_dev, im, IGMP_HOST_MEMBERSHIP_REPORT);
 	else if (IGMP_V2_SEEN(in_dev))

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#1655070

On Thu, Jun 1, 2017 at 2:13 AM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
> On Wed, 2017-05-31 at 16:55 -0700, Eric Dumazet wrote:
>
>> The issue here is the timer firing while ip_mc_clear_src() has been
>> already called.
>>
>> My patch should fix the problem.
>>
>> Or another one using del_timer_sync() instead of del_timer() in
>> igmp_stop_timer(), but such a change would be more invasive,
>> since the del_timer_sync() would need to happen while im->lock
>> spinlock is not held.
>
> BTW, I guess that Andrey could try to add a delay to trigger the bug
> more often.

Applied, now testing with your patch.

Thanks!

>
> diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
> index 44fd86de2823dd17de16276a8ec01b190e69b8b4..84fff17daab0832c470a613b29b2aaade07cec0a 100644
> --- a/net/ipv4/igmp.c
> +++ b/net/ipv4/igmp.c
> @@ -798,7 +798,7 @@ static void igmp_timer_expire(unsigned long data)
>         }
>         im->reporter = 1;
>         spin_unlock(&im->lock);
> -
> +       udelay(10000);
>         if (IGMP_V1_SEEN(in_dev))
>                 igmp_send_report(in_dev, im, IGMP_HOST_MEMBERSHIP_REPORT);
>         else if (IGMP_V2_SEEN(in_dev))
>
>
> --
> You received this message because you are subscribed to the Google Groups "syzkaller" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller+unsubscribe@googlegroups.com.
> For more options, visit https://groups.google.com/d/optout.

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#1654730

On Wed, May 31, 2017 at 9:12 AM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
> On Wed, 2017-05-31 at 11:46 +0200, Andrey Konovalov wrote:
>> Hi,
>>
>> I've got the following error report while fuzzing the kernel with syzkaller.
>>
>> On commit 5ed02dbb497422bf225783f46e6eadd237d23d6b (4.12-rc3).
>>
>> Unfortunately it's not reproducible.
>>
>> ==================================================================
>> BUG: KASAN: use-after-free in add_grec+0x101e/0x1090 net/ipv4/igmp.c:473
>> Read of size 8 at addr ffff88003053c1a0 by task swapper/0/0
>>
>> CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.12.0-rc3+ #370
>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
>> Call Trace:
>>  <IRQ>
>>  __dump_stack lib/dump_stack.c:16 [inline]
>>  dump_stack+0x292/0x395 lib/dump_stack.c:52
>>  print_address_description+0x73/0x280 mm/kasan/report.c:252
>>  kasan_report_error mm/kasan/report.c:351 [inline]
>>  kasan_report+0x22b/0x340 mm/kasan/report.c:408
>>  __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:429
>>  add_grec+0x101e/0x1090 net/ipv4/igmp.c:473
>>  igmpv3_send_cr net/ipv4/igmp.c:663 [inline]
>>  igmp_ifc_timer_expire+0x46d/0xa80 net/ipv4/igmp.c:768
>> IPVS: length: 51 != 8
>>  call_timer_fn+0x23f/0x800 kernel/time/timer.c:1268
>>  expire_timers kernel/time/timer.c:1307 [inline]
>>  __run_timers+0x94e/0xcd0 kernel/time/timer.c:1601
>>  run_timer_softirq+0x21/0x80 kernel/time/timer.c:1614
>>  __do_softirq+0x2fb/0xb99 kernel/softirq.c:284
>>  invoke_softirq kernel/softirq.c:364 [inline]
>>  irq_exit+0x19e/0x1d0 kernel/softirq.c:405
>>  exiting_irq arch/x86/include/asm/apic.h:652 [inline]
>>  smp_apic_timer_interrupt+0x76/0xa0 arch/x86/kernel/apic/apic.c:966
>>  apic_timer_interrupt+0x93/0xa0 arch/x86/entry/entry_64.S:481
>> RIP: 0010:native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:53
>> RSP: 0018:ffffffff85a079a8 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff10
>> RAX: dffffc0000000020 RBX: 1ffffffff0b40f38 RCX: 0000000000000000
>> RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffffff85a2a9e4
>> RBP: ffffffff85a079a8 R08: 0000000000000000 R09: 0000000000000000
>> R10: 0000000000000000 R11: 0000000000000000 R12: dffffc0000000000
>> R13: ffffffff85a07a60 R14: ffffffff86171338 R15: 1ffffffff0b40f5b
>>  </IRQ>
>>  arch_safe_halt arch/x86/include/asm/paravirt.h:98 [inline]
>>  default_idle+0x8f/0x440 arch/x86/kernel/process.c:341
>>  arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:332
>>  default_idle_call+0x36/0x60 kernel/sched/idle.c:98
>>  cpuidle_idle_call kernel/sched/idle.c:156 [inline]
>>  do_idle+0x348/0x420 kernel/sched/idle.c:245
>>  cpu_startup_entry+0x18/0x20 kernel/sched/idle.c:350
>>  rest_init+0x18d/0x1a0 init/main.c:415
>>  start_kernel+0x747/0x779 init/main.c:679
>>  x86_64_start_reservations+0x2a/0x2c arch/x86/kernel/head64.c:196
>>  x86_64_start_kernel+0x132/0x141 arch/x86/kernel/head64.c:177
>>  secondary_startup_64+0x9f/0x9f arch/x86/kernel/head_64.S:304
>>
>> Allocated by task 30543:
>>  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:617
>>  kmem_cache_alloc_trace+0x82/0x270 mm/slub.c:2745
>>  kmalloc include/linux/slab.h:492 [inline]
>>  kzalloc include/linux/slab.h:665 [inline]
>>  ip_mc_add1_src net/ipv4/igmp.c:1909 [inline]
>>  ip_mc_add_src+0x6cd/0x1020 net/ipv4/igmp.c:2033
>>  ip_mc_msfilter+0x5e5/0xcf0 net/ipv4/igmp.c:2403
>>  do_ip_setsockopt.isra.12+0x2d47/0x38c0 net/ipv4/ip_sockglue.c:959
>>  ip_setsockopt+0x3a/0xb0 net/ipv4/ip_sockglue.c:1256
>>  tcp_setsockopt+0x82/0xd0 net/ipv4/tcp.c:2740
>>  sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2844
>>  SYSC_setsockopt net/socket.c:1798 [inline]
>>  SyS_setsockopt+0x270/0x3a0 net/socket.c:1777
>>  entry_SYSCALL_64_fastpath+0x1f/0xbe
>>
>> Freed by task 30543:
>>  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+0x72/0xc0 mm/kasan/kasan.c:590
>>  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_clear_src+0x69/0x1c0 net/ipv4/igmp.c:2078
>>  ip_mc_dec_group+0x19a/0x470 net/ipv4/igmp.c:1618
>>  ip_mc_drop_socket+0x145/0x230 net/ipv4/igmp.c:2609
>>  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+0x18a3/0x2820 kernel/exit.c:878
>>  do_group_exit+0x149/0x420 kernel/exit.c:982
>>  get_signal+0x76d/0x1790 kernel/signal.c:2318
>>  do_signal+0xd2/0x2130 arch/x86/kernel/signal.c:808
>>  exit_to_usermode_loop+0x17a/0x210 arch/x86/entry/common.c:157
>>  prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline]
>>  syscall_return_slowpath+0x3ba/0x410 arch/x86/entry/common.c:263
>>  entry_SYSCALL_64_fastpath+0xbc/0xbe
>>
>> The buggy address belongs to the object at ffff88003053c1a0
>>  which belongs to the cache kmalloc-64 of size 64
>> The buggy address is located 0 bytes inside of
>>  64-byte region [ffff88003053c1a0, ffff88003053c1e0)
>> The buggy address belongs to the page:
>> page:ffffea0000c14f00 count:1 mapcount:0 mapping:          (null)
>> index:0x0 compound_mapcount: 0
>> flags: 0x100000000008100(slab|head)
>> raw: 0100000000008100 0000000000000000 0000000000000000 0000000100140014
>> raw: ffffea0000c2f520 ffffea0000e20aa0 ffff88003e80f740 0000000000000000
>> page dumped because: kasan: bad access detected
>>
>> Memory state around the buggy address:
>>  ffff88003053c080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>>  ffff88003053c100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>> >ffff88003053c180: fc fc fc fc fb fb fb fb fb fb fb fb fc fc fc fc
>>                                ^
>>  ffff88003053c200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>>  ffff88003053c280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>> ==================================================================
>
> I have the feeling that ip_mc_clear_src() is called too soon.
>
> We should call it once all users have released their reference.

In this case, ip_mc_clear_src() is called when the ->users hits
zero, therefore I think we possibly miss the refcnt on ->users.

diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index 44fd86d..c2f3347 100644
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -1886,6 +1886,7 @@ static int ip_mc_del_src(struct in_device
*in_dev, __be32 *pmca, int sfmode,
                igmp_ifc_event(pmc->interface);
 #endif
        }
+       pmc->users--;
 out_unlock:
        spin_unlock_bh(&pmc->lock);
        return err;
@@ -2025,6 +2026,7 @@ static int ip_mc_add_src(struct in_device
*in_dev, __be32 *pmca, int sfmode,
 #ifdef CONFIG_IP_MULTICAST
        sf_markstate(pmc);
 #endif
+       pmc->users++;
        isexclude = pmc->sfmode == MCAST_EXCLUDE;
        if (!delta)
                pmc->sfcount[sfmode]++;

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