KASAN: use-after-free Read in pppol2tp_session_close

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: f4cc0ed9 Linux 4.14.131
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1722a7eba00000
kernel config: https://syzkaller.appspot.com/x/.config?x=ab1953b2cdac00f5
dashboard link: https://syzkaller.appspot.com/bug?extid=a604433e06f5a46be61f
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

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+a60443...@syzkaller.appspotmail.com

audit: type=1804 audit(1561978416.765:163): pid=20073 uid=0 auid=4294967295
ses=4294967295 subj=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023
op="invalid_pcr" cause="open_writers" comm="syz-executor.4" name="bus"
dev="sda1" ino=16828 res=1
==================================================================
BUG: KASAN: use-after-free in inet_shutdown+0x2d3/0x350
net/ipv4/af_inet.c:816
Read of size 4 at addr ffff88805d99b1c0 by task syz-executor.1/20071

CPU: 1 PID: 20071 Comm: syz-executor.1 Not tainted 4.14.131 #25
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+0x138/0x19c 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_load4_noabort+0x14/0x20 mm/kasan/report.c:429
inet_shutdown+0x2d3/0x350 net/ipv4/af_inet.c:816
pppol2tp_session_close+0xa0/0xe0 net/l2tp/l2tp_ppp.c:441
l2tp_tunnel_closeall+0x243/0x380 net/l2tp/l2tp_core.c:1340
l2tp_udp_encap_destroy+0x99/0x100 net/l2tp/l2tp_core.c:1366
udp_destroy_sock net/ipv4/udp.c:2330 [inline]
udp_destroy_sock+0x10f/0x1a0 net/ipv4/udp.c:2320
sk_common_release+0x6b/0x310 net/core/sock.c:2987
udp_lib_close+0x16/0x20 include/net/udp.h:203
inet_release+0xec/0x1c0 net/ipv4/af_inet.c:425
__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
RIP: 0033:0x459519
RSP: 002b:00007f41f89f0c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000001 RCX: 0000000000459519
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f41f89f16d4
R13: 00000000004f85b2 R14: 00000000004d1370 R15: 00000000ffffffff

Allocated by task 20071:
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
kasan_slab_alloc+0xf/0x20 mm/kasan/kasan.c:489
kmem_cache_alloc+0x12e/0x780 mm/slab.c:3552
sock_alloc_inode+0x1d/0x260 net/socket.c:251
alloc_inode+0x64/0x180 fs/inode.c:209
new_inode_pseudo+0x19/0xf0 fs/inode.c:891
sock_alloc+0x41/0x280 net/socket.c:569
__sock_create+0x8f/0x620 net/socket.c:1239
sock_create net/socket.c:1315 [inline]
SYSC_socket net/socket.c:1345 [inline]
SyS_socket+0xd3/0x170 net/socket.c:1325
do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 20077:
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]
kmem_cache_free+0x83/0x2b0 mm/slab.c:3758
sock_destroy_inode+0x54/0x60 net/socket.c:281
destroy_inode+0xc2/0x120 fs/inode.c:266
evict+0x3e6/0x630 fs/inode.c:571
iput_final fs/inode.c:1516 [inline]
iput fs/inode.c:1543 [inline]
iput+0x471/0x900 fs/inode.c:1528
dentry_unlink_inode+0x286/0x340 fs/dcache.c:387
__dentry_kill+0x32e/0x580 fs/dcache.c:591
dentry_kill fs/dcache.c:632 [inline]
dput.part.0+0x59f/0x750 fs/dcache.c:847
dput+0x20/0x30 fs/dcache.c:811
__fput+0x45f/0x7a0 fs/file_table.c:228
____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 ffff88805d99b1c0
which belongs to the cache sock_inode_cache of size 992
The buggy address is located 0 bytes inside of
992-byte region [ffff88805d99b1c0, ffff88805d99b5a0)
The buggy address belongs to the page:
page:ffffea00017666c0 count:1 mapcount:0 mapping:ffff88805d99b1c0
index:0xffff88805d99bffd
flags: 0x1fffc0000000100(slab)
raw: 01fffc0000000100 ffff88805d99b1c0 ffff88805d99bffd 0000000100000003
raw: ffffea00017668a0 ffffea000173b160 ffff88821b7193c0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88805d99b080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88805d99b100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff88805d99b180: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
^
ffff88805d99b200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88805d99b280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
audit: type=1804 audit(1561978417.385:164): pid=20088 uid=0 auid=4294967295
ses=4294967295 subj=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023
op="invalid_pcr" cause="open_writers" comm="syz-executor.3" name="bus"
dev="sda1" ino=16847 res=1
audit: type=1804 audit(1561978417.395:165): pid=20087 uid=0 auid=4294967295
ses=4294967295 subj=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023
op="invalid_pcr" cause="open_writers" comm="syz-executor.4" name="bus"
dev="sda1" ino=16945 res=1
audit: type=1804 audit(1561978417.445:166): pid=20090 uid=0 auid=4294967295
ses=4294967295 subj=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023
op="invalid_pcr" cause="open_writers" comm="syz-executor.4" name="bus"
dev="sda1" ino=16838 res=1


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
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syzbot will keep track of this bug report. See:
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[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit: 01fd1694 Linux 4.14.141
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=12c3ba76600000
kernel config: https://syzkaller.appspot.com/x/.config?x=62c9b69e1b2adda9

dashboard link: https://syzkaller.appspot.com/bug?extid=a604433e06f5a46be61f
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16cc292a600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+a60443...@syzkaller.appspotmail.com

l2tp_core: tunl 3: sockfd_lookup(fd=3) returned -9
l2tp_core: tunl 3: sockfd_lookup(fd=3) returned -9
l2tp_core: tunl 3: sockfd_lookup(fd=3) returned -9
l2tp_core: tunl 3: sockfd_lookup(fd=3) returned -9

==================================================================
BUG: KASAN: use-after-free in inet_shutdown+0x2d3/0x350
net/ipv4/af_inet.c:816

Read of size 4 at addr ffff88809a0da080 by task syz-executor.1/9911

CPU: 1 PID: 9911 Comm: syz-executor.1 Not tainted 4.14.141 #37

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_load4_noabort+0x14/0x20 mm/kasan/report.c:429
inet_shutdown+0x2d3/0x350 net/ipv4/af_inet.c:816
pppol2tp_session_close+0xa0/0xe0 net/l2tp/l2tp_ppp.c:441
l2tp_tunnel_closeall+0x243/0x380 net/l2tp/l2tp_core.c:1340
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

RIP: 0033:0x459879
RSP: 002b:00007f4da7661c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: 0000000000000000 RBX: 0000000000000003 RCX: 0000000000459879
RDX: 0000000000000032 RSI: 0000000020000080 RDI: 0000000000000004

RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 00007f4da76626d4
R13: 00000000004bfdeb R14: 00000000004d1c48 R15: 00000000ffffffff

Allocated by task 9911:

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
kasan_slab_alloc+0xf/0x20 mm/kasan/kasan.c:489
kmem_cache_alloc+0x12e/0x780 mm/slab.c:3552
sock_alloc_inode+0x1d/0x260 net/socket.c:251
alloc_inode+0x64/0x180 fs/inode.c:209
new_inode_pseudo+0x19/0xf0 fs/inode.c:891
sock_alloc+0x41/0x280 net/socket.c:569
__sock_create+0x8f/0x620 net/socket.c:1239
sock_create net/socket.c:1315 [inline]
SYSC_socket net/socket.c:1345 [inline]
SyS_socket+0xd3/0x170 net/socket.c:1325
do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 9904:

The buggy address belongs to the object at ffff88809a0da080

which belongs to the cache sock_inode_cache of size 992
The buggy address is located 0 bytes inside of

992-byte region [ffff88809a0da080, ffff88809a0da460)

The buggy address belongs to the page:

page:ffffea0002683680 count:1 mapcount:0 mapping:ffff88809a0da080
index:0xffff88809a0daffd
flags: 0x1fffc0000000100(slab)
raw: 01fffc0000000100 ffff88809a0da080 ffff88809a0daffd 0000000100000003
raw: ffffea0002685560 ffffea0002685460 ffff8880a9e82c00 0000000000000000

page dumped because: kasan: bad access detected

Memory state around the buggy address:

ffff88809a0d9f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88809a0da000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff88809a0da080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88809a0da100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88809a0da180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================