KASAN: use-after-free Read in sctp_packet_transmit

[syzbot]

Hello,

syzkaller hit the following crash on
8a4816cad00bf14642f0ed6043b32d29a05006ce
git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.
Unfortunately, I don't have any reproducer for this bug yet.


IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+5adcca...@syzkaller.appspotmail.com
It will help syzbot understand when the bug is fixed. See footer for
details.
If you forward the report, please keep this part and the footer.

==================================================================
BUG: KASAN: use-after-free in sctp_packet_transmit+0x3505/0x3750
net/sctp/output.c:643
Read of size 8 at addr ffff8801bda9fb80 by task modprobe/23740

CPU: 1 PID: 23740 Comm: modprobe Not tainted 4.15.0-rc5+ #175
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
<IRQ>
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x194/0x257 lib/dump_stack.c:53
print_address_description+0x73/0x250 mm/kasan/report.c:252
kasan_report_error mm/kasan/report.c:351 [inline]
kasan_report+0x25b/0x340 mm/kasan/report.c:409
__asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
sctp_packet_transmit+0x3505/0x3750 net/sctp/output.c:643
sctp_outq_flush+0x121b/0x4060 net/sctp/outqueue.c:1197
sctp_outq_uncork+0x5a/0x70 net/sctp/outqueue.c:776
sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1807 [inline]
sctp_side_effects net/sctp/sm_sideeffect.c:1210 [inline]
sctp_do_sm+0x4e0/0x6ed0 net/sctp/sm_sideeffect.c:1181
sctp_generate_heartbeat_event+0x292/0x3f0 net/sctp/sm_sideeffect.c:406
call_timer_fn+0x228/0x820 kernel/time/timer.c:1320
expire_timers kernel/time/timer.c:1357 [inline]
__run_timers+0x7ee/0xb70 kernel/time/timer.c:1660
run_timer_softirq+0x4c/0xb0 kernel/time/timer.c:1686
__do_softirq+0x2d7/0xb85 kernel/softirq.c:285
invoke_softirq kernel/softirq.c:365 [inline]
irq_exit+0x1cc/0x200 kernel/softirq.c:405
exiting_irq arch/x86/include/asm/apic.h:540 [inline]
smp_apic_timer_interrupt+0x16b/0x700 arch/x86/kernel/apic/apic.c:1052
apic_timer_interrupt+0xa9/0xb0 arch/x86/entry/entry_64.S:904
</IRQ>
RIP: 0010:__preempt_count_add arch/x86/include/asm/preempt.h:76 [inline]
RIP: 0010:__rcu_read_lock include/linux/rcupdate.h:83 [inline]
RIP: 0010:rcu_read_lock include/linux/rcupdate.h:629 [inline]
RIP: 0010:__is_insn_slot_addr+0x8f/0x330 kernel/kprobes.c:303
RSP: 0018:ffff8801d4937430 EFLAGS: 00000283 ORIG_RAX: ffffffffffffff11
RAX: ffff8801bf13c000 RBX: ffffffff8656dd00 RCX: ffffffff8170bd88
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff8656dd00
RBP: ffff8801d4937518 R08: 0000000000000000 R09: 1ffff1003a926e67
R10: ffff8801d4937300 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: ffff8801d49374f0 R15: ffff8801dae230c0
is_kprobe_insn_slot include/linux/kprobes.h:318 [inline]
kernel_text_address+0x132/0x140 kernel/extable.c:150
__kernel_text_address+0xd/0x40 kernel/extable.c:107
unwind_get_return_address+0x61/0xa0 arch/x86/kernel/unwind_frame.c:18
__save_stack_trace+0x7e/0xd0 arch/x86/kernel/stacktrace.c:45
save_stack_trace+0x1a/0x20 arch/x86/kernel/stacktrace.c:60
save_stack+0x43/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
kmem_cache_alloc+0x12e/0x760 mm/slab.c:3544
kmem_cache_zalloc include/linux/slab.h:678 [inline]
file_alloc_security security/selinux/hooks.c:369 [inline]
selinux_file_alloc_security+0xae/0x190 security/selinux/hooks.c:3454
security_file_alloc+0x6d/0xa0 security/security.c:873
get_empty_filp+0x189/0x4f0 fs/file_table.c:129
path_openat+0xed/0x3530 fs/namei.c:3496
do_filp_open+0x25b/0x3b0 fs/namei.c:3554
do_sys_open+0x502/0x6d0 fs/open.c:1059
SYSC_open fs/open.c:1077 [inline]
SyS_open+0x2d/0x40 fs/open.c:1072
entry_SYSCALL_64_fastpath+0x23/0x9a
RIP: 0033:0x7efdff1bb120
RSP: 002b:00007ffde6213c08 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 000055c34fab4090 RCX: 00007efdff1bb120
RDX: 00000000000001b6 RSI: 0000000000080000 RDI: 00007ffde6213d20
RBP: 00007ffde6214d90 R08: 0000000000000008 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000246 R12: 000055c34fab4090
R13: 00007ffde6215de0 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 23739:
save_stack+0x43/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
kmem_cache_alloc+0x12e/0x760 mm/slab.c:3544
kmem_cache_zalloc include/linux/slab.h:678 [inline]
sctp_chunkify+0xce/0x3f0 net/sctp/sm_make_chunk.c:1329
_sctp_make_chunk+0x13c/0x260 net/sctp/sm_make_chunk.c:1397
sctp_make_control+0x39/0x150 net/sctp/sm_make_chunk.c:1433
sctp_make_heartbeat+0x90/0x420 net/sctp/sm_make_chunk.c:1151
sctp_sf_heartbeat.isra.24+0x26/0x180 net/sctp/sm_statefuns.c:973
sctp_sf_do_prm_requestheartbeat+0x27/0x100 net/sctp/sm_statefuns.c:5251
sctp_do_sm+0x192/0x6ed0 net/sctp/sm_sideeffect.c:1178
sctp_primitive_REQUESTHEARTBEAT+0xa0/0xd0 net/sctp/primitive.c:200
sctp_apply_peer_addr_params+0x759/0xf30 net/sctp/socket.c:2462
sctp_setsockopt_peer_addr_params+0x36f/0x5f0 net/sctp/socket.c:2658
sctp_setsockopt+0x199a/0x61a0 net/sctp/socket.c:4173
sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2978
SYSC_setsockopt net/socket.c:1821 [inline]
SyS_setsockopt+0x189/0x360 net/socket.c:1800
entry_SYSCALL_64_fastpath+0x23/0x9a

Freed by task 23739:
save_stack+0x43/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
__cache_free mm/slab.c:3488 [inline]
kmem_cache_free+0x83/0x2a0 mm/slab.c:3746
sctp_chunk_destroy net/sctp/sm_make_chunk.c:1450 [inline]
sctp_chunk_put+0x2fd/0x420 net/sctp/sm_make_chunk.c:1473
sctp_chunk_free+0x53/0x60 net/sctp/sm_make_chunk.c:1460
sctp_packet_transmit+0xf5d/0x3750 net/sctp/output.c:646
sctp_outq_flush+0x121b/0x4060 net/sctp/outqueue.c:1197
sctp_outq_uncork+0x5a/0x70 net/sctp/outqueue.c:776
sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1807 [inline]
sctp_side_effects net/sctp/sm_sideeffect.c:1210 [inline]
sctp_do_sm+0x4e0/0x6ed0 net/sctp/sm_sideeffect.c:1181
sctp_primitive_REQUESTHEARTBEAT+0xa0/0xd0 net/sctp/primitive.c:200
sctp_apply_peer_addr_params+0x759/0xf30 net/sctp/socket.c:2462
sctp_setsockopt_peer_addr_params+0x36f/0x5f0 net/sctp/socket.c:2658
sctp_setsockopt+0x199a/0x61a0 net/sctp/socket.c:4173
sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2978
SYSC_setsockopt net/socket.c:1821 [inline]
SyS_setsockopt+0x189/0x360 net/socket.c:1800
entry_SYSCALL_64_fastpath+0x23/0x9a

The buggy address belongs to the object at ffff8801bda9fb80
which belongs to the cache sctp_chunk of size 256
The buggy address is located 0 bytes inside of
256-byte region [ffff8801bda9fb80, ffff8801bda9fc80)
The buggy address belongs to the page:
page:00000000d1261812 count:1 mapcount:0 mapping:000000003e733284 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801bda9f040 0000000000000000 000000010000000c
raw: ffffea000714c9e0 ffffea0006fa8520 ffff8801d3246c80 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8801bda9fa80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8801bda9fb00: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
> ffff8801bda9fb80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8801bda9fc00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8801bda9fc80: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
==================================================================


---
This bug is generated by a dumb bot. It may contain errors.
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[Xin Long]

Couldn't see how this happened, but I noticed one buggy thing:
when peeling off an assoc, it doesn't reset the sk owner for the
chunks in q->control_chunk_list. It causes these skbs to have
the incorrect skb->sk. This might be relevant.

[Dmitry Vyukov]

On Sat, Jan 6, 2018 at 6:02 PM, Marcelo Ricardo Leitner
<marcelo...@gmail.com> wrote:

> On Fri, Jan 05, 2018 at 02:07:01PM -0800, syzbot wrote:
>> Hello,
>>
>> syzkaller hit the following crash on
>> 8a4816cad00bf14642f0ed6043b32d29a05006ce
>> git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git/master
>> compiler: gcc (GCC) 7.1.1 20170620
>> .config is attached
>> Raw console output is attached.
>> Unfortunately, I don't have any reproducer for this bug yet.
>

> How can we tell if there wasn't any list corruption messages before
> the panic?

Hi Marcelo,

syzbot always gives reports on non-tainted kernels. So, no, there was
nothing bad before this.

[Marcelo]

OK. Thanks

--
Enviado de meu dispositivo Android com K-9 mail. Desculpe-me pela brevidade.

[Denis Kirjanov]

On 1/5/18, syzbot <syzbot+5adcca...@syzkaller.appspotmail.com> wrote:
> Hello,
>
> syzkaller hit the following crash on
> 8a4816cad00bf14642f0ed6043b32d29a05006ce
> git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git/master
> compiler: gcc (GCC) 7.1.1 20170620
> .config is attached
> Raw console output is attached.
> Unfortunately, I don't have any reproducer for this bug yet.
>
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+5adcca...@syzkaller.appspotmail.com
> It will help syzbot understand when the bug is fixed. See footer for
> details.
> If you forward the report, please keep this part and the footer.
>
> ==================================================================
> BUG: KASAN: use-after-free in sctp_packet_transmit+0x3505/0x3750
> net/sctp/output.c:643
> Read of size 8 at addr ffff8801bda9fb80 by task modprobe/23740
>

This can be related to the following corruption during send:
#6 [ffff8805945ff940] invalid_op at ffffffff8100c15b
[exception RIP: sctp_chunk_put+91]
RIP: ffffffffa039db3b RSP: ffff8805945ff9f8 RFLAGS: 00010212
RAX: ffff8808b025cb01 RBX: ffff880dbb1b0d80 RCX: ffff8805945ff818
RDX: 0000000000000020 RSI: ffff8809a84746d8 RDI: ffff880dbb1b0d80
RBP: ffff8805945ffa08 R8: ffff880dbb13a0c0 R9: 0000000000000000
R10: ffff880000023820 R11: 0000000000000000 R12: ffff880dbb1b0d80
R13: 0000000000000000 R14: ffff8808b025cb80 R15: 0000000000000000
ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018
#7 [ffff8805945ffa10] sctp_datamsg_put at ffffffffa039c543 [sctp]
#8 [ffff8805945ffa60] sctp_datamsg_free at ffffffffa039c9dd [sctp]
#9 [ffff8805945ffa80] sctp_sendmsg at ffffffffa03a9440 [sctp]
#10 [ffff8805945ffb70] inet_sendmsg at ffffffff814ef0ba
#11 [ffff8805945ffbb0] sock_sendmsg at ffffffff8146b4c7
#12 [ffff8805945ffd60] __sys_sendmsg at ffffffff8146b976
#13 [ffff8805945fff10] sys_sendmsg at ffffffff8146bb99

In this case we have the chunk with 0 refcounter:
struct sctp_chunk {
list = {
next = 0xffff8809a84746d8,
prev = 0xffff880dbb1b0e80
},
refcnt = {
counter = 0
},
transmitted_list = {
next = 0xffff880dbb1b0d98,
prev = 0xffff880dbb1b0d98
},
frag_list = {
next = 0xffff880dbb1b0da8,
prev = 0xffff880dbb1b0da8
},
skb = 0xffff880dbb1a4700,
param_hdr = {
v = 0x0,
p = 0x0,
life = 0x0,
dns = 0x0,
cookie = 0x0,
....

Previous chunk in the list has the refcounter set to 2:
struct sctp_chunk {
list = {
next = 0xffff880dbb1b0d80,
prev = 0xffff880c657160c0
},
refcnt = {
counter = 2
},
transmitted_list = {
next = 0xffff880dbb1b0e98,
prev = 0xffff880dbb1b0e98
},
frag_list = {
next = 0xffff8808b025c300,
prev = 0xffff8808b025c300
},
skb = 0xffff880dbb1a4840,
param_hdr = {
v = 0x0,
p = 0x0,
life = 0x0,
dns = 0x0,
cookie = 0x0,
...

[Marcelo Ricardo Leitner]

On Fri, Jan 05, 2018 at 02:07:01PM -0800, syzbot wrote:

> Hello,
>
> syzkaller hit the following crash on
> 8a4816cad00bf14642f0ed6043b32d29a05006ce
> git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git/master
> compiler: gcc (GCC) 7.1.1 20170620
> .config is attached
> Raw console output is attached.
> Unfortunately, I don't have any reproducer for this bug yet.

How can we tell if there wasn't any list corruption messages before
the panic?

Marcelo

[Eric Biggers]

On Fri, Jan 05, 2018 at 02:07:01PM -0800, syzbot wrote:

No reproducer, this only happened once (Jan 5 on net-next), and there have been
a lot of SCTP fixes in the mean time including commit 6910e25de225 ("sctp:
remove sctp_chunk_put from fail_mark err path in sctp_ulpevent_make_rcvmsg")
which may be relevant since it fixed a case of incorrect reference counting of
'struct sctp_chunk', which is the struct in which the use-after-free occurred
here. So I'm just invalidating this bug:

#syz invalid

- Eric