KASAN: use-after-free Read in nr_rx_frame (2)

From: syzbot
Date: Tue Jul 23 2019 - 04:49:09 EST

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Hello,

syzbot found the following crash on:

HEAD commit: 3bfe1fc4 Merge tag 'for-5.3/dm-changes-2' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10413e34600000
kernel config: https://syzkaller.appspot.com/x/.config?x=21511d77e11db3cb
dashboard link: https://syzkaller.appspot.com/bug?extid=701728447042217b67c1
compiler: clang version 9.0.0 (/home/glider/llvm/clang 80fee25776c2fb61e74c1ecb1a523375c2500b69)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+701728447042217b67c1@xxxxxxxxxxxxxxxxxxxxxxxxx

==================================================================
BUG: KASAN: use-after-free in atomic_read /./include/asm-generic/atomic-instrumented.h:26 [inline]
BUG: KASAN: use-after-free in refcount_inc_not_zero_checked+0x7c/0x280 /lib/refcount.c:123
Read of size 4 at addr ffff88808ee52080 by task swapper/1/0

CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.2.0+ #35
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
<IRQ>
__dump_stack /lib/dump_stack.c:77 [inline]
dump_stack+0x1d8/0x2f8 /lib/dump_stack.c:113
print_address_description+0x75/0x5b0 /mm/kasan/report.c:351
__kasan_report+0x14b/0x1c0 /mm/kasan/report.c:482
kasan_report+0x26/0x50 /mm/kasan/common.c:612
check_memory_region_inline /mm/kasan/generic.c:182 [inline]
check_memory_region+0x2cf/0x2e0 /mm/kasan/generic.c:192
__kasan_check_read+0x11/0x20 /mm/kasan/common.c:92
atomic_read /./include/asm-generic/atomic-instrumented.h:26 [inline]
refcount_inc_not_zero_checked+0x7c/0x280 /lib/refcount.c:123
refcount_inc_checked+0x15/0x50 /lib/refcount.c:156
sock_hold /./include/net/sock.h:649 [inline]
sk_add_node /./include/net/sock.h:701 [inline]
nr_insert_socket /net/netrom/af_netrom.c:137 [inline]
nr_rx_frame+0x17bc/0x1e40 /net/netrom/af_netrom.c:1023
nr_loopback_timer+0x6a/0x140 /net/netrom/nr_loopback.c:59
call_timer_fn+0xec/0x200 /kernel/time/timer.c:1322
expire_timers /kernel/time/timer.c:1366 [inline]
__run_timers+0x7cd/0x9c0 /kernel/time/timer.c:1685
run_timer_softirq+0x4a/0x90 /kernel/time/timer.c:1698
__do_softirq+0x333/0x7c4 /./arch/x86/include/asm/paravirt.h:777
invoke_softirq /kernel/softirq.c:373 [inline]
irq_exit+0x227/0x230 /kernel/softirq.c:413
exiting_irq /./arch/x86/include/asm/apic.h:537 [inline]
smp_apic_timer_interrupt+0x113/0x280 /arch/x86/kernel/apic/apic.c:1095
apic_timer_interrupt+0xf/0x20 /arch/x86/entry/entry_64.S:828
</IRQ>
RIP: 0010:native_safe_halt+0xe/0x10 /./arch/x86/include/asm/irqflags.h:61
Code: 06 fa eb ae 89 d9 80 e1 07 80 c1 03 38 c1 7c ba 48 89 df e8 c4 41 06 fa eb b0 90 90 e9 07 00 00 00 0f 00 2d 76 67 56 00 fb f4 <c3> 90 e9 07 00 00 00 0f 00 2d 66 67 56 00 f4 c3 90 90 55 48 89 e5
RSP: 0018:ffff8880a98cfd38 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff13
RAX: 1ffffffff11950db RBX: ffff8880a98bc340 RCX: dffffc0000000000
RDX: 0000000000000000 RSI: ffffffff812d193a RDI: ffff8880a98bcb78
RBP: ffff8880a98cfd40 R08: ffff8880a98bcb90 R09: ffffed1015317869
R10: ffffed1015317869 R11: 0000000000000000 R12: 0000000000000001
R13: 1ffff11015317868 R14: dffffc0000000000 R15: dffffc0000000000
arch_cpu_idle+0xa/0x10 /arch/x86/kernel/process.c:571
default_idle_call+0x59/0xa0 /kernel/sched/idle.c:94
cpuidle_idle_call /kernel/sched/idle.c:154 [inline]
do_idle+0x180/0x780 /kernel/sched/idle.c:263
cpu_startup_entry+0x25/0x30 /kernel/sched/idle.c:354
start_secondary+0x3f4/0x490 /arch/x86/kernel/smpboot.c:264
secondary_startup_64+0xa4/0xb0 /arch/x86/kernel/head_64.S:243

Allocated by task 0:
save_stack /mm/kasan/common.c:69 [inline]
set_track /mm/kasan/common.c:77 [inline]
__kasan_kmalloc+0x11c/0x1b0 /mm/kasan/common.c:487
kasan_kmalloc+0x9/0x10 /mm/kasan/common.c:501
__do_kmalloc /mm/slab.c:3655 [inline]
__kmalloc+0x254/0x340 /mm/slab.c:3664
kmalloc /./include/linux/slab.h:557 [inline]
sk_prot_alloc+0xb0/0x290 /net/core/sock.c:1603
sk_alloc+0x38/0x950 /net/core/sock.c:1657
nr_make_new /net/netrom/af_netrom.c:476 [inline]
nr_rx_frame+0xabc/0x1e40 /net/netrom/af_netrom.c:959
nr_loopback_timer+0x6a/0x140 /net/netrom/nr_loopback.c:59
call_timer_fn+0xec/0x200 /kernel/time/timer.c:1322
expire_timers /kernel/time/timer.c:1366 [inline]
__run_timers+0x7cd/0x9c0 /kernel/time/timer.c:1685
run_timer_softirq+0x4a/0x90 /kernel/time/timer.c:1698
__do_softirq+0x333/0x7c4 /./arch/x86/include/asm/paravirt.h:777

Freed by task 4044:
save_stack /mm/kasan/common.c:69 [inline]
set_track /mm/kasan/common.c:77 [inline]
__kasan_slab_free+0x12a/0x1e0 /mm/kasan/common.c:449
kasan_slab_free+0xe/0x10 /mm/kasan/common.c:457
__cache_free /mm/slab.c:3425 [inline]
kfree+0x115/0x200 /mm/slab.c:3756
sk_prot_free /net/core/sock.c:1640 [inline]
__sk_destruct+0x567/0x660 /net/core/sock.c:1726
sk_destruct /net/core/sock.c:1734 [inline]
__sk_free+0x317/0x3e0 /net/core/sock.c:1745
sk_free /net/core/sock.c:1756 [inline]
sock_put /./include/net/sock.h:1725 [inline]
sock_efree+0x60/0x80 /net/core/sock.c:2042
skb_release_head_state+0x100/0x220 /net/core/skbuff.c:652
skb_release_all /net/core/skbuff.c:663 [inline]
__kfree_skb+0x25/0x170 /net/core/skbuff.c:679
kfree_skb+0x6f/0xb0 /net/core/skbuff.c:697
nr_accept+0x4ef/0x650 /net/netrom/af_netrom.c:819
__sys_accept4+0x5bc/0x9a0 /net/socket.c:1750
__do_sys_accept /net/socket.c:1791 [inline]
__se_sys_accept /net/socket.c:1788 [inline]
__x64_sys_accept+0x7d/0x90 /net/socket.c:1788
do_syscall_64+0xfe/0x140 /arch/x86/entry/common.c:296
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff88808ee52000
which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 128 bytes inside of
2048-byte region [ffff88808ee52000, ffff88808ee52800)
The buggy address belongs to the page:
page:ffffea00023b9480 refcount:1 mapcount:0 mapping:ffff8880aa400e00 index:0xffff88808ee53100 compound_mapcount: 0
flags: 0x1fffc0000010200(slab|head)
raw: 01fffc0000010200 ffffea0001732108 ffffea00025f5588 ffff8880aa400e00
raw: ffff88808ee53100 ffff88808ee52000 0000000100000002 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88808ee51f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88808ee52000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

ffff88808ee52080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

^
ffff88808ee52100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88808ee52180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

---
This bug is generated by a bot. It may contain errors.
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Next message: Jason Wang: "Re: WARNING in __mmdrop"
Previous message: Geert Uytterhoeven: "Build regressions/improvements in v5.3-rc1"
Next in thread: Dmitry Vyukov: "Re: KASAN: use-after-free Read in nr_rx_frame (2)"
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