Re: [syzbot] [net?] KASAN: slab-use-after-free Write in l2tp_session_delete

syzbot
2024-06-27T13:30:04Z

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: slab-use-after-free Write in l2tp_session_delete

==================================================================
BUG: KASAN: slab-use-after-free in instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
BUG: KASAN: slab-use-after-free in test_and_set_bit include/asm-generic/bitops/instrumented-atomic.h:71 [inline]
BUG: KASAN: slab-use-after-free in l2tp_session_delete+0x28/0x9e0 net/l2tp/l2tp_core.c:1639
Write of size 8 at addr ffff88806ca77808 by task kworker/u8:3/51

CPU: 0 PID: 51 Comm: kworker/u8:3 Not tainted 6.10.0-rc4-syzkaller-00869-g185d72112b95-dirty #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
kasan_check_range+0x282/0x290 mm/kasan/generic.c:189
instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
test_and_set_bit include/asm-generic/bitops/instrumented-atomic.h:71 [inline]
l2tp_session_delete+0x28/0x9e0 net/l2tp/l2tp_core.c:1639
l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1302 [inline]
l2tp_tunnel_del_work+0x1cb/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 6223:
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:783
__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 5956:
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
__do_softirq kernel/softirq.c:588 [inline]
invoke_softirq kernel/softirq.c:428 [inline]
__irq_exit_rcu+0xf4/0x1c0 kernel/softirq.c:637
irq_exit_rcu+0x9/0x30 kernel/softirq.c:649
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1043 [inline]
sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1043
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702

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+0x357/0x450 net/l2tp/l2tp_ppp.c:458
__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 ffff88806ca77800
which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 8 bytes inside of
freed 1024-byte region [ffff88806ca77800, ffff88806ca77c00)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x6ca70
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 ffffea0001b29c01 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 0x152820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_HARDWALL), pid 11, tgid 11 (kworker/u8:0), ts 101409670398, free_ts 101342435367
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_noprof+0x257/0x400 mm/slub.c:4135
kmalloc_noprof include/linux/slab.h:664 [inline]
kzalloc_noprof include/linux/slab.h:778 [inline]
neigh_alloc net/core/neighbour.c:494 [inline]
___neigh_create+0x691/0x2470 net/core/neighbour.c:648
ip6_finish_output2+0x1631/0x1680 net/ipv6/ip6_output.c:128
ip6_finish_output+0x41e/0x810 net/ipv6/ip6_output.c:222
NF_HOOK include/linux/netfilter.h:314 [inline]
ndisc_send_skb+0xab2/0x1380 net/ipv6/ndisc.c:509
ndisc_send_ns+0xcc/0x160 net/ipv6/ndisc.c:667
addrconf_dad_work+0xb45/0x16f0 net/ipv6/addrconf.c:4281
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
page last free pid 9 tgid 9 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_node_noprof+0x16b/0x320 mm/slub.c:4044
__alloc_skb+0x1c3/0x440 net/core/skbuff.c:656
alloc_skb include/linux/skbuff.h:1320 [inline]
alloc_skb_with_frags+0xc3/0x770 net/core/skbuff.c:6509
sock_alloc_send_pskb+0x91a/0xa60 net/core/sock.c:2815
sock_alloc_send_skb include/net/sock.h:1773 [inline]
mld_newpack+0x1c3/0xa90 net/ipv6/mcast.c:1746
add_grhead net/ipv6/mcast.c:1849 [inline]
add_grec+0x1492/0x19a0 net/ipv6/mcast.c:1987
mld_send_initial_cr+0x228/0x4b0 net/ipv6/mcast.c:2233
mld_dad_work+0x44/0x500 net/ipv6/mcast.c:2259
process_one_work kernel/workqueue.c:3231 [inline]
process_scheduled_works+0xa2c/0x1830 kernel/workqueue.c:3312

Memory state around the buggy address:
ffff88806ca77700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88806ca77780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88806ca77800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88806ca77880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88806ca77900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Tested on:

commit: 185d7211 net: xilinx: axienet: Enable multicast by def..
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
console output: https://syzkaller.appspot.com/x/log.txt?x=135c05a9980000
kernel config: https://syzkaller.appspot.com/x/.config?x=e78fc116033e0ab7
dashboard link: https://syzkaller.appspot.com/bug?extid=c041b4ce3a6dfd1e63e2
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch: https://syzkaller.appspot.com/x/patch.diff?x=13129e12980000