[syzbot] [net?] KASAN: slab-use-after-free Read in l2tp_tunnel_del_work

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: b0d3969d2b4d net: ethernet: rtsn: Add support for Renesas ..
git tree: net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1790b32e980000
kernel config: https://syzkaller.appspot.com/x/.config?x=e78fc116033e0ab7
dashboard link: https://syzkaller.appspot.com/bug?extid=b471b7c936301a59745b
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14a90fb1980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7aada183897f/disk-b0d3969d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9518258e6c30/vmlinux-b0d3969d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9d4a19845f65/bzImage-b0d3969d.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b471b7...@syzkaller.appspotmail.com

wlan1: Created IBSS using preconfigured BSSID 50:50:50:50:50:50
wlan1: Creating new IBSS network, BSSID 50:50:50:50:50:50
==================================================================
BUG: KASAN: slab-use-after-free in l2tp_tunnel_del_work+0xe5/0x330 net/l2tp/l2tp_core.c:1334
Read of size 8 at addr ffff88801ff3c0b8 by task kworker/u8:0/11

CPU: 0 PID: 11 Comm: kworker/u8:0 Not tainted 6.10.0-rc4-syzkaller-00836-gb0d3969d2b4d #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
Workqueue: l2tp l2tp_tunnel_del_work
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
print_address_description mm/kasan/report.c:377 [inline]
print_report+0x169/0x550 mm/kasan/report.c:488
kasan_report+0x143/0x180 mm/kasan/report.c:601
l2tp_tunnel_del_work+0xe5/0x330 net/l2tp/l2tp_core.c:1334
process_one_work kernel/workqueue.c:3231 [inline]
process_scheduled_works+0xa2c/0x1830 kernel/workqueue.c:3312
worker_thread+0x86d/0xd70 kernel/workqueue.c:3393
kthread+0x2f0/0x390 kernel/kthread.c:389
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
</TASK>

Allocated by task 5308:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
poison_kmalloc_redzone mm/kasan/common.c:370 [inline]
__kasan_kmalloc+0x98/0xb0 mm/kasan/common.c:387
kasan_kmalloc include/linux/kasan.h:211 [inline]
__do_kmalloc_node mm/slub.c:4122 [inline]
__kmalloc_noprof+0x1f9/0x400 mm/slub.c:4135
kmalloc_noprof include/linux/slab.h:664 [inline]
kzalloc_noprof include/linux/slab.h:778 [inline]
l2tp_session_create+0x3b/0xc20 net/l2tp/l2tp_core.c:1675
pppol2tp_connect+0xca3/0x17a0 net/l2tp/l2tp_ppp.c:782
__sys_connect_file net/socket.c:2049 [inline]
__sys_connect+0x2df/0x310 net/socket.c:2066
__do_sys_connect net/socket.c:2076 [inline]
__se_sys_connect net/socket.c:2073 [inline]
__x64_sys_connect+0x7a/0x90 net/socket.c:2073
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 24:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:579
poison_slab_object+0xe0/0x150 mm/kasan/common.c:240
__kasan_slab_free+0x37/0x60 mm/kasan/common.c:256
kasan_slab_free include/linux/kasan.h:184 [inline]
slab_free_hook mm/slub.c:2196 [inline]
slab_free mm/slub.c:4437 [inline]
kfree+0x149/0x360 mm/slub.c:4558
__sk_destruct+0x58/0x5f0 net/core/sock.c:2191
rcu_do_batch kernel/rcu/tree.c:2535 [inline]
rcu_core+0xafd/0x1830 kernel/rcu/tree.c:2809
handle_softirqs+0x2c4/0x970 kernel/softirq.c:554
run_ksoftirqd+0xca/0x130 kernel/softirq.c:928
smpboot_thread_fn+0x544/0xa30 kernel/smpboot.c:164
kthread+0x2f0/0x390 kernel/kthread.c:389
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Last potentially related work creation:
kasan_save_stack+0x3f/0x60 mm/kasan/common.c:47
__kasan_record_aux_stack+0xac/0xc0 mm/kasan/generic.c:541
__call_rcu_common kernel/rcu/tree.c:3072 [inline]
call_rcu+0x167/0xa70 kernel/rcu/tree.c:3176
pppol2tp_release+0x24b/0x350 net/l2tp/l2tp_ppp.c:457
__sock_release net/socket.c:659 [inline]
sock_close+0xbc/0x240 net/socket.c:1421
__fput+0x406/0x8b0 fs/file_table.c:422
task_work_run+0x24f/0x310 kernel/task_work.c:180
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
exit_to_user_mode_loop kernel/entry/common.c:114 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
syscall_exit_to_user_mode+0x168/0x370 kernel/entry/common.c:218
do_syscall_64+0x100/0x230 arch/x86/entry/common.c:89
entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88801ff3c000
which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 184 bytes inside of
freed 1024-byte region [ffff88801ff3c000, ffff88801ff3c400)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1ff38
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffefff(slab)
raw: 00fff00000000040 ffff888015041dc0 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000100010 00000001ffffefff 0000000000000000
head: 00fff00000000040 ffff888015041dc0 dead000000000122 0000000000000000
head: 0000000000000000 0000000000100010 00000001ffffefff 0000000000000000
head: 00fff00000000003 ffffea00007fce01 ffffffffffffffff 0000000000000000
head: 0000000000000008 0000000000000000 00000000ffffffff 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 0x1d2820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 62, tgid 62 (kworker/u8:4), ts 170500836332, free_ts 170485857715
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x1f3/0x230 mm/page_alloc.c:1468
prep_new_page mm/page_alloc.c:1476 [inline]
get_page_from_freelist+0x2e43/0x2f00 mm/page_alloc.c:3420
__alloc_pages_noprof+0x256/0x6c0 mm/page_alloc.c:4678
__alloc_pages_node_noprof include/linux/gfp.h:269 [inline]
alloc_pages_node_noprof include/linux/gfp.h:296 [inline]
alloc_slab_page+0x5f/0x120 mm/slub.c:2265
allocate_slab+0x5a/0x2f0 mm/slub.c:2428
new_slab mm/slub.c:2481 [inline]
___slab_alloc+0xcd1/0x14b0 mm/slub.c:3667
__slab_alloc+0x58/0xa0 mm/slub.c:3757
__slab_alloc_node mm/slub.c:3810 [inline]
slab_alloc_node mm/slub.c:3989 [inline]
__do_kmalloc_node mm/slub.c:4121 [inline]
kmalloc_node_track_caller_noprof+0x281/0x440 mm/slub.c:4142
kmalloc_reserve+0x111/0x2a0 net/core/skbuff.c:597
__alloc_skb+0x1f3/0x440 net/core/skbuff.c:666
alloc_skb include/linux/skbuff.h:1320 [inline]
nlmsg_new include/net/netlink.h:1015 [inline]
inet6_rt_notify+0xdf/0x290 net/ipv6/route.c:6180
fib6_add_rt2node net/ipv6/ip6_fib.c:1266 [inline]
fib6_add+0x1e33/0x4430 net/ipv6/ip6_fib.c:1495
__ip6_ins_rt net/ipv6/route.c:1314 [inline]
ip6_ins_rt+0x106/0x170 net/ipv6/route.c:1324
__ipv6_ifa_notify+0x5d2/0x1230 net/ipv6/addrconf.c:6267
ipv6_ifa_notify net/ipv6/addrconf.c:6306 [inline]
addrconf_dad_completed+0x181/0xcd0 net/ipv6/addrconf.c:4319
addrconf_dad_work+0xdc2/0x16f0
page last free pid 5306 tgid 5306 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1088 [inline]
free_unref_page+0xd22/0xea0 mm/page_alloc.c:2583
discard_slab mm/slub.c:2527 [inline]
__put_partials+0xeb/0x130 mm/slub.c:2995
put_cpu_partial+0x17c/0x250 mm/slub.c:3070
__slab_free+0x2ea/0x3d0 mm/slub.c:4307
qlink_free mm/kasan/quarantine.c:163 [inline]
qlist_free_all+0x9e/0x140 mm/kasan/quarantine.c:179
kasan_quarantine_reduce+0x14f/0x170 mm/kasan/quarantine.c:286
__kasan_slab_alloc+0x23/0x80 mm/kasan/common.c:322
kasan_slab_alloc include/linux/kasan.h:201 [inline]
slab_post_alloc_hook mm/slub.c:3941 [inline]
slab_alloc_node mm/slub.c:4001 [inline]
kmem_cache_alloc_noprof+0x135/0x2a0 mm/slub.c:4008
ptlock_alloc mm/memory.c:6444 [inline]
ptlock_init include/linux/mm.h:2968 [inline]
pmd_ptlock_init include/linux/mm.h:3068 [inline]
pagetable_pmd_ctor include/linux/mm.h:3106 [inline]
pmd_alloc_one_noprof include/asm-generic/pgalloc.h:141 [inline]
__pmd_alloc+0x110/0x630 mm/memory.c:5925
pmd_alloc include/linux/mm.h:2866 [inline]
__handle_mm_fault mm/memory.c:5483 [inline]
handle_mm_fault+0xf4c/0x1ba0 mm/memory.c:5688
do_user_addr_fault arch/x86/mm/fault.c:1338 [inline]
handle_page_fault arch/x86/mm/fault.c:1481 [inline]
exc_page_fault+0x459/0x8c0 arch/x86/mm/fault.c:1539
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623

Memory state around the buggy address:
ffff88801ff3bf80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88801ff3c000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88801ff3c080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88801ff3c100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88801ff3c180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

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If you want to undo deduplication, reply with:
#syz undup

[Hillf Danton]

On Tue, 25 Jun 2024 03:40:20 -0700

> syzbot found the following issue on:
>
> HEAD commit: b0d3969d2b4d net: ethernet: rtsn: Add support for Renesas ..
> git tree: net-next

> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14a90fb1980000

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git 185d72112b95

--- x/net/l2tp/l2tp_core.c
+++ y/net/l2tp/l2tp_core.c
@@ -1298,8 +1298,10 @@ static void l2tp_tunnel_closeall(struct
list_for_each_safe(pos, tmp, &tunnel->session_list) {
session = list_entry(pos, struct l2tp_session, list);
list_del_init(&session->list);
+ l2tp_session_inc_refcount(session);
spin_unlock_bh(&tunnel->list_lock);
l2tp_session_delete(session);
+ l2tp_session_dec_refcount(session);
spin_lock_bh(&tunnel->list_lock);
}
spin_unlock_bh(&tunnel->list_lock);
--- x/net/l2tp/l2tp_ppp.c
+++ y/net/l2tp/l2tp_ppp.c
@@ -393,14 +393,6 @@ abort:
* Session (and tunnel control) socket create/destroy.
*****************************************************************************/

-static void pppol2tp_put_sk(struct rcu_head *head)
-{
- struct pppol2tp_session *ps;
-
- ps = container_of(head, typeof(*ps), rcu);
- sock_put(ps->__sk);
-}
-
/* Really kill the session socket. (Called from sock_put() if
* refcnt == 0.)
*/
@@ -444,22 +436,8 @@ static int pppol2tp_release(struct socke

session = pppol2tp_sock_to_session(sk);
if (session) {
- struct pppol2tp_session *ps;
-
l2tp_session_delete(session);
-
- ps = l2tp_session_priv(session);
- mutex_lock(&ps->sk_lock);
- ps->__sk = rcu_dereference_protected(ps->sk,
- lockdep_is_held(&ps->sk_lock));
- RCU_INIT_POINTER(ps->sk, NULL);
- mutex_unlock(&ps->sk_lock);
- call_rcu(&ps->rcu, pppol2tp_put_sk);
-
- /* Rely on the sock_put() call at the end of the function for
- * dropping the reference held by pppol2tp_sock_to_session().
- * The last reference will be dropped by pppol2tp_put_sk().
- */
+ l2tp_session_dec_refcount(session);
}

release_sock(sk);
@@ -831,6 +809,7 @@ static int pppol2tp_connect(struct socke
out_no_ppp:
/* This is how we get the session context from the socket. */
sk->sk_user_data = session;
+ l2tp_session_inc_refcount(session);
rcu_assign_pointer(ps->sk, sk);
mutex_unlock(&ps->sk_lock);

--

[syzbot]

Hello,

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

Reported-and-tested-by: syzbot+b471b7...@syzkaller.appspotmail.com

Tested on:

commit: 185d7211 net: xilinx: axienet: Enable multicast by def..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git
console output: https://syzkaller.appspot.com/x/log.txt?x=14609ac6980000

kernel config: https://syzkaller.appspot.com/x/.config?x=e78fc116033e0ab7
dashboard link: https://syzkaller.appspot.com/bug?extid=b471b7c936301a59745b
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=148aa8b9980000

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