Hello,
syzbot found the following crash on:
HEAD commit: f6e27dbb Linux 4.14.146
git tree: linux-4.14.y
console output:
https://syzkaller.appspot.com/x/log.txt?x=130a72d5600000
kernel config:
https://syzkaller.appspot.com/x/.config?x=cb75afefe94a0801
dashboard link:
https://syzkaller.appspot.com/bug?extid=1103ad221a6999d73f67
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:
https://syzkaller.appspot.com/x/repro.syz?x=149d664d600000
IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by:
syzbot+1103ad...@syzkaller.appspotmail.com
l2tp_core: tunl 4: sockfd_lookup(fd=4) returned -9
l2tp_core: tunl 4: sockfd_lookup(fd=4) returned -9
l2tp_core: tunl 4: sockfd_lookup(fd=4) returned -9
l2tp_core: tunl 4: sockfd_lookup(fd=4) returned -9
==================================================================
BUG: KASAN: use-after-free in pppol2tp_connect+0x169c/0x18b0
net/l2tp/l2tp_ppp.c:764
Read of size 8 at addr ffff888073c39858 by task syz-executor.5/8995
CPU: 0 PID: 8995 Comm: syz-executor.5 Not tainted 4.14.146 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x138/0x197 lib/dump_stack.c:53
print_address_description.cold+0x7c/0x1dc mm/kasan/report.c:252
kasan_report_error mm/kasan/report.c:351 [inline]
kasan_report mm/kasan/report.c:409 [inline]
kasan_report.cold+0xa9/0x2af mm/kasan/report.c:393
__asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
pppol2tp_connect+0x169c/0x18b0 net/l2tp/l2tp_ppp.c:764
SYSC_connect+0x1f6/0x2d0 net/socket.c:1655
SyS_connect+0x24/0x30 net/socket.c:1636
do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x459a29
RSP: 002b:00007fabb543ac78 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000459a29
RDX: 0000000000000026 RSI: 0000000020000180 RDI: 0000000000000005
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fabb543b6d4
R13: 00000000004bff90 R14: 00000000004d1f00 R15: 00000000ffffffff
Allocated by task 8995:
save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
save_stack+0x45/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
kasan_kmalloc mm/kasan/kasan.c:551 [inline]
kasan_kmalloc+0xce/0xf0 mm/kasan/kasan.c:529
__do_kmalloc mm/slab.c:3720 [inline]
__kmalloc+0x15d/0x7a0 mm/slab.c:3729
kmalloc include/linux/slab.h:493 [inline]
kzalloc include/linux/slab.h:661 [inline]
l2tp_session_create+0x38/0x1600 net/l2tp/l2tp_core.c:1791
pppol2tp_connect+0x11bf/0x18b0 net/l2tp/l2tp_ppp.c:721
SYSC_connect+0x1f6/0x2d0 net/socket.c:1655
SyS_connect+0x24/0x30 net/socket.c:1636
do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
Freed by task 9004:
save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
save_stack+0x45/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
kasan_slab_free+0x75/0xc0 mm/kasan/kasan.c:524
__cache_free mm/slab.c:3496 [inline]
kfree+0xcc/0x270 mm/slab.c:3815
l2tp_session_free+0x176/0x210 net/l2tp/l2tp_core.c:1714
l2tp_session_dec_refcount_1 net/l2tp/l2tp_core.h:300 [inline]
l2tp_tunnel_closeall+0x2ca/0x380 net/l2tp/l2tp_core.c:1345
l2tp_udp_encap_destroy+0x99/0x100 net/l2tp/l2tp_core.c:1366
udpv6_destroy_sock+0xb3/0xd0 net/ipv6/udp.c:1444
sk_common_release+0x6b/0x310 net/core/sock.c:2984
udp_lib_close+0x16/0x20 include/net/udp.h:203
inet_release+0xec/0x1c0 net/ipv4/af_inet.c:425
inet6_release+0x53/0x80 net/ipv6/af_inet6.c:450
__sock_release+0xce/0x2b0 net/socket.c:602
sock_close+0x1b/0x30 net/socket.c:1139
__fput+0x275/0x7a0 fs/file_table.c:210
____fput+0x16/0x20 fs/file_table.c:244
task_work_run+0x114/0x190 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:191 [inline]
exit_to_usermode_loop+0x1da/0x220 arch/x86/entry/common.c:164
prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline]
syscall_return_slowpath arch/x86/entry/common.c:270 [inline]
do_syscall_64+0x4bc/0x640 arch/x86/entry/common.c:297
entry_SYSCALL_64_after_hwframe+0x42/0xb7
The buggy address belongs to the object at ffff888073c39840
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 24 bytes inside of
512-byte region [ffff888073c39840, ffff888073c39a40)
The buggy address belongs to the page:
page:ffffea0001cf0e40 count:1 mapcount:0 mapping:ffff888073c390c0 index:0x0
flags: 0x1fffc0000000100(slab)
raw: 01fffc0000000100 ffff888073c390c0 0000000000000000 0000000100000006
raw: ffffea00025a6520 ffffea0001d129a0 ffff8880aa800940 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff888073c39700: 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc
ffff888073c39780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff888073c39800: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
^
ffff888073c39880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888073c39900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
---
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