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

From: syzbot <[email-masked]>
Date: Tue, 25 Jun 2024 03:40:20 -0700

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: [email-masked]

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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