[syzbot] KASAN: use-after-free Write in l2tp_tunnel_del_work (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 355479c70a48 Merge tag 'efi-fixes-for-v6.1-4' of git://git..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17f65c47880000
kernel config: https://syzkaller.appspot.com/x/.config?x=cc4b2e0a8e8a8366
dashboard link: https://syzkaller.appspot.com/bug?extid=57d48d64daabde805330
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1731caf3880000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/cc9435668c09/disk-355479c7.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/efa65db8752c/vmlinux-355479c7.xz
kernel image: https://storage.googleapis.com/syzbot-assets/819f2fe5b542/bzImage-355479c7.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+57d48d...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in instrument_atomic_read_write include/linux/instrumented.h:102 [inline]
BUG: KASAN: use-after-free in test_and_set_bit include/asm-generic/bitops/instrumented-atomic.h:71 [inline]
BUG: KASAN: use-after-free in l2tp_session_delete net/l2tp/l2tp_core.c:1555 [inline]
BUG: KASAN: use-after-free in l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1207 [inline]
BUG: KASAN: use-after-free in l2tp_tunnel_del_work+0x1e8/0x780 net/l2tp/l2tp_core.c:1239
Write of size 8 at addr ffff888079457808 by task kworker/u4:4/102

CPU: 1 PID: 102 Comm: kworker/u4:4 Not tainted 6.1.0-rc7-syzkaller-00122-g355479c70a48 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
Workqueue: l2tp l2tp_tunnel_del_work
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xd1/0x138 lib/dump_stack.c:106
print_address_description mm/kasan/report.c:284 [inline]
print_report+0x15e/0x45d mm/kasan/report.c:395
kasan_report+0xbf/0x1f0 mm/kasan/report.c:495
check_region_inline mm/kasan/generic.c:183 [inline]
kasan_check_range+0x141/0x190 mm/kasan/generic.c:189
instrument_atomic_read_write include/linux/instrumented.h:102 [inline]
test_and_set_bit include/asm-generic/bitops/instrumented-atomic.h:71 [inline]
l2tp_session_delete net/l2tp/l2tp_core.c:1555 [inline]
l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1207 [inline]
l2tp_tunnel_del_work+0x1e8/0x780 net/l2tp/l2tp_core.c:1239
process_one_work+0x9bf/0x1710 kernel/workqueue.c:2289
worker_thread+0x669/0x1090 kernel/workqueue.c:2436
kthread+0x2e8/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
</TASK>

Allocated by task 15805:
kasan_save_stack+0x22/0x40 mm/kasan/common.c:45
kasan_set_track+0x25/0x30 mm/kasan/common.c:52
____kasan_kmalloc mm/kasan/common.c:371 [inline]
____kasan_kmalloc mm/kasan/common.c:330 [inline]
__kasan_kmalloc+0xa5/0xb0 mm/kasan/common.c:380
kasan_kmalloc include/linux/kasan.h:211 [inline]
__do_kmalloc_node mm/slab_common.c:955 [inline]
__kmalloc+0x5a/0xd0 mm/slab_common.c:968
kmalloc include/linux/slab.h:558 [inline]
kzalloc include/linux/slab.h:689 [inline]
l2tp_session_create+0x3a/0xb70 net/l2tp/l2tp_core.c:1591
pppol2tp_connect+0xfff/0x1a10 net/l2tp/l2tp_ppp.c:771
__sys_connect_file+0x153/0x1a0 net/socket.c:1976
__sys_connect+0x165/0x1a0 net/socket.c:1993
__do_sys_connect net/socket.c:2003 [inline]
__se_sys_connect net/socket.c:2000 [inline]
__x64_sys_connect+0x73/0xb0 net/socket.c:2000
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

Freed by task 15:
kasan_save_stack+0x22/0x40 mm/kasan/common.c:45
kasan_set_track+0x25/0x30 mm/kasan/common.c:52
kasan_save_free_info+0x2e/0x40 mm/kasan/generic.c:511
____kasan_slab_free mm/kasan/common.c:236 [inline]
____kasan_slab_free+0x160/0x1c0 mm/kasan/common.c:200
kasan_slab_free include/linux/kasan.h:177 [inline]
slab_free_hook mm/slub.c:1724 [inline]
slab_free_freelist_hook+0x8b/0x1c0 mm/slub.c:1750
slab_free mm/slub.c:3661 [inline]
__kmem_cache_free+0xaf/0x3b0 mm/slub.c:3674
l2tp_session_free net/l2tp/l2tp_core.c:163 [inline]
l2tp_session_dec_refcount+0x15d/0x3a0 net/l2tp/l2tp_core.c:200
pppol2tp_session_destruct+0xbe/0x100 net/l2tp/l2tp_ppp.c:418
__sk_destruct+0x51/0x710 net/core/sock.c:2122
sk_destruct net/core/sock.c:2167 [inline]
__sk_free+0x175/0x460 net/core/sock.c:2178
sk_free+0x7c/0xa0 net/core/sock.c:2189
sock_put include/net/sock.h:1987 [inline]
pppol2tp_put_sk+0x9f/0xd0 net/l2tp/l2tp_ppp.c:401
rcu_do_batch kernel/rcu/tree.c:2250 [inline]
rcu_core+0x81f/0x1980 kernel/rcu/tree.c:2510
__do_softirq+0x1fb/0xadc kernel/softirq.c:571

Last potentially related work creation:
kasan_save_stack+0x22/0x40 mm/kasan/common.c:45
__kasan_record_aux_stack+0xbc/0xd0 mm/kasan/generic.c:481
call_rcu+0x9d/0x820 kernel/rcu/tree.c:2798
pppol2tp_release+0x315/0x560 net/l2tp/l2tp_ppp.c:457
__sock_release+0xcd/0x280 net/socket.c:650
sock_close+0x1c/0x20 net/socket.c:1365
__fput+0x27c/0xa90 fs/file_table.c:320
task_work_run+0x16f/0x270 kernel/task_work.c:179
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
exit_to_user_mode_loop kernel/entry/common.c:171 [inline]
exit_to_user_mode_prepare+0x23c/0x250 kernel/entry/common.c:203
__syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline]
syscall_exit_to_user_mode+0x1d/0x50 kernel/entry/common.c:296
do_syscall_64+0x46/0xb0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x63/0xcd

Second to last potentially related work creation:
kasan_save_stack+0x22/0x40 mm/kasan/common.c:45
__kasan_record_aux_stack+0xbc/0xd0 mm/kasan/generic.c:481
call_rcu+0x9d/0x820 kernel/rcu/tree.c:2798
pppol2tp_release+0x315/0x560 net/l2tp/l2tp_ppp.c:457
__sock_release+0xcd/0x280 net/socket.c:650
sock_close+0x1c/0x20 net/socket.c:1365
__fput+0x27c/0xa90 fs/file_table.c:320
task_work_run+0x16f/0x270 kernel/task_work.c:179
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
exit_to_user_mode_loop kernel/entry/common.c:171 [inline]
exit_to_user_mode_prepare+0x23c/0x250 kernel/entry/common.c:203
__syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline]
syscall_exit_to_user_mode+0x1d/0x50 kernel/entry/common.c:296
do_syscall_64+0x46/0xb0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x63/0xcd

The buggy address belongs to the object at ffff888079457800
which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 8 bytes inside of
1024-byte region [ffff888079457800, ffff888079457c00)

The buggy address belongs to the physical page:
page:ffffea0001e51400 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x79450
head:ffffea0001e51400 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 0000000000000000 dead000000000001 ffff888012041dc0
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0x1d2a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 3729, tgid 3729 (kworker/0:6), ts 188509457070, free_ts 184865002121
prep_new_page mm/page_alloc.c:2539 [inline]
get_page_from_freelist+0x10b5/0x2d50 mm/page_alloc.c:4291
__alloc_pages+0x1cb/0x5b0 mm/page_alloc.c:5558
alloc_pages+0x1aa/0x270 mm/mempolicy.c:2285
alloc_slab_page mm/slub.c:1794 [inline]
allocate_slab+0x213/0x300 mm/slub.c:1939
new_slab mm/slub.c:1992 [inline]
___slab_alloc+0xa91/0x1400 mm/slub.c:3180
__slab_alloc.constprop.0+0x56/0xa0 mm/slub.c:3279
slab_alloc_node mm/slub.c:3364 [inline]
__kmem_cache_alloc_node+0x199/0x3e0 mm/slub.c:3437
__do_kmalloc_node mm/slab_common.c:954 [inline]
__kmalloc_node_track_caller+0x4b/0xc0 mm/slab_common.c:975
kmalloc_reserve net/core/skbuff.c:437 [inline]
__alloc_skb+0xdd/0x300 net/core/skbuff.c:509
alloc_skb include/linux/skbuff.h:1267 [inline]
nlmsg_new include/net/netlink.h:970 [inline]
inet6_rt_notify+0xf0/0x2b0 net/ipv6/route.c:6172
fib6_add_rt2node net/ipv6/ip6_fib.c:1252 [inline]
fib6_add+0x26eb/0x3f20 net/ipv6/ip6_fib.c:1478
__ip6_ins_rt net/ipv6/route.c:1302 [inline]
ip6_route_add+0x8f/0x150 net/ipv6/route.c:3847
addrconf_add_mroute+0x1e1/0x310 net/ipv6/addrconf.c:2489
addrconf_add_dev+0x156/0x1c0 net/ipv6/addrconf.c:2507
addrconf_dev_config+0x1ec/0x410 net/ipv6/addrconf.c:3382
addrconf_notify+0xee0/0x1c80 net/ipv6/addrconf.c:3635
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1459 [inline]
free_pcp_prepare+0x65c/0xd90 mm/page_alloc.c:1509
free_unref_page_prepare mm/page_alloc.c:3387 [inline]
free_unref_page+0x1d/0x4d0 mm/page_alloc.c:3483
__unfreeze_partials+0x17c/0x1a0 mm/slub.c:2586
qlink_free mm/kasan/quarantine.c:168 [inline]
qlist_free_all+0x6a/0x170 mm/kasan/quarantine.c:187
kasan_quarantine_reduce+0x184/0x210 mm/kasan/quarantine.c:294
__kasan_slab_alloc+0x66/0x90 mm/kasan/common.c:302
kasan_slab_alloc include/linux/kasan.h:201 [inline]
slab_post_alloc_hook mm/slab.h:737 [inline]
slab_alloc_node mm/slub.c:3398 [inline]
__kmem_cache_alloc_node+0x2e2/0x3e0 mm/slub.c:3437
__do_kmalloc_node mm/slab_common.c:954 [inline]
__kmalloc+0x4a/0xd0 mm/slab_common.c:968
kmalloc include/linux/slab.h:558 [inline]
kzalloc include/linux/slab.h:689 [inline]
fib_create_info+0xdc2/0x4ac0 net/ipv4/fib_semantics.c:1451
fib_table_insert+0x199/0x1be0 net/ipv4/fib_trie.c:1236
fib_magic+0x455/0x540 net/ipv4/fib_frontend.c:1098
fib_add_ifaddr+0x49f/0x540 net/ipv4/fib_frontend.c:1142
fib_netdev_event+0x36d/0x6a0 net/ipv4/fib_frontend.c:1480
notifier_call_chain+0xb5/0x200 kernel/notifier.c:87
call_netdevice_notifiers_info+0xb5/0x130 net/core/dev.c:1945
call_netdevice_notifiers_extack net/core/dev.c:1983 [inline]
call_netdevice_notifiers net/core/dev.c:1997 [inline]
__dev_notify_flags+0x114/0x2c0 net/core/dev.c:8581

Memory state around the buggy address:
ffff888079457700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888079457780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888079457800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888079457880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888079457900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches

[Hillf Danton]

On 06 Dec 2022 08:02:35 -0800

> syzbot found the following issue on:
>
> HEAD commit: 355479c70a48 Merge tag 'efi-fixes-for-v6.1-4' of git://git..
> git tree: upstream

> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1731caf3880000

pppol2tp_release() l2tp_tunnel_closeall()
l2tp_session_delete(session);
if (test_and_set_bit(0, &session->dead))
return;
spin_lock_bh(&tunnel->hlist_lock);
hlist_del_init_rcu(&session->hlist);
spin_unlock_bh(&tunnel->hlist_lock);
l2tp_session_unhash()
spin_lock_bh(&tunnel->hlist_lock);
hlist_del_init_rcu(&session->hlist);
spin_unlock_bh(&tunnel->hlist_lock);

l2tp_session_dec_refcount(session);

uaf <-- l2tp_session_delete(session);


Fix the uaf by checking session dead in both release and closeall pathes.

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 355479c70a48

--- x/net/l2tp/l2tp_core.c
+++ y/net/l2tp/l2tp_core.c
@@ -1189,6 +1189,7 @@ static void l2tp_session_unhash(struct l
}
}

+static void __l2tp_session_delete(struct l2tp_session *);
/* When the tunnel is closed, all the attached sessions need to go too.
*/
static void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel)
@@ -1201,10 +1202,12 @@ static void l2tp_tunnel_closeall(struct
for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
again:
hlist_for_each_entry_rcu(session, &tunnel->session_hlist[hash], hlist) {
+ if (test_and_set_bit(0, &session->dead))
+ continue;
hlist_del_init_rcu(&session->hlist);

spin_unlock_bh(&tunnel->hlist_lock);
- l2tp_session_delete(session);
+ __l2tp_session_delete(session);
spin_lock_bh(&tunnel->hlist_lock);

/* Now restart from the beginning of this hash
@@ -1550,11 +1553,8 @@ void l2tp_tunnel_delete(struct l2tp_tunn
}
EXPORT_SYMBOL_GPL(l2tp_tunnel_delete);

-void l2tp_session_delete(struct l2tp_session *session)
+static void __l2tp_session_delete(struct l2tp_session *session)
{
- if (test_and_set_bit(0, &session->dead))
- return;
-
trace_delete_session(session);
l2tp_session_unhash(session);
l2tp_session_queue_purge(session);
@@ -1563,6 +1563,13 @@ void l2tp_session_delete(struct l2tp_ses

l2tp_session_dec_refcount(session);
}
+
+void l2tp_session_delete(struct l2tp_session *session)
+{
+ if (test_and_set_bit(0, &session->dead))
+ return;
+ __l2tp_session_delete(session);
+}
EXPORT_SYMBOL_GPL(l2tp_session_delete);

/* We come here whenever a session's send_seq, cookie_len or
--

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+57d48d...@syzkaller.appspotmail.com

Tested on:

commit: 355479c7 Merge tag 'efi-fixes-for-v6.1-4' of git://git..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=16391af3880000

kernel config: https://syzkaller.appspot.com/x/.config?x=cc4b2e0a8e8a8366
dashboard link: https://syzkaller.appspot.com/bug?extid=57d48d64daabde805330
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

patch: https://syzkaller.appspot.com/x/patch.diff?x=1311216b880000

Note: testing is done by a robot and is best-effort only.

[syzbot]

syzbot suspects this issue was fixed by commit:

commit d772781964415c63759572b917e21c4f7ec08d9f
Author: Jakub Kicinski <ku...@kernel.org>
Date: Fri Jan 6 06:33:54 2023 +0000

devlink: bump the instance index directly when iterating

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=12e69652c80000
start commit: 355479c70a48 Merge tag 'efi-fixes-for-v6.1-4' of git://git..
git tree: upstream

kernel config: https://syzkaller.appspot.com/x/.config?x=cc4b2e0a8e8a8366
dashboard link: https://syzkaller.appspot.com/bug?extid=57d48d64daabde805330

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1731caf3880000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: devlink: bump the instance index directly when iterating

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

[syzbot]

Auto-closing this bug as obsolete.
No recent activity, existing reproducers are no longer triggering the issue.