Extracting prog: 1m14.543373988s
Minimizing prog: 3m48.202732454s
Simplifying prog options: 0s
Extracting C: 44.63924598s
Simplifying C: 2m40.743336623s


extracting reproducer from 1 programs
testing a last program of every proc
single: executing 1 programs separately with timeout 30s
testing program (duration=30s, {Threaded:true Repeat:true RepeatTimes:0 Procs:5 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:false Wifi:false IEEE802154:false Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): socket$pppl2tp-socket$inet6_udp-connect$pppl2tp-ioctl$XFS_IOC_START_COMMIT
detailed listing:
executing program 0:
r0 = socket$pppl2tp(0x18, 0x1, 0x1)
r1 = socket$inet6_udp(0xa, 0x2, 0x0)
connect$pppl2tp(r0, &(0x7f0000000000)=@pppol2tpv3={0x18, 0x1, {0x3, r1, {0x2, 0x0, @dev}, 0x2}}, 0x2e)
ioctl$XFS_IOC_START_COMMIT(r0, 0x80585882, 0x0)

program crashed: KASAN: use-after-free Write in pppol2tp_release
single: successfully extracted reproducer
found reproducer with 4 syscalls
minimizing guilty program
testing program (duration=30.642292512s, {Threaded:true Repeat:true RepeatTimes:0 Procs:5 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:false Wifi:false IEEE802154:false Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): socket$pppl2tp-socket$inet6_udp-connect$pppl2tp
detailed listing:
executing program 0:
r0 = socket$pppl2tp(0x18, 0x1, 0x1)
r1 = socket$inet6_udp(0xa, 0x2, 0x0)
connect$pppl2tp(r0, &(0x7f0000000000)=@pppol2tpv3={0x18, 0x1, {0x3, r1, {0x2, 0x0, @dev}, 0x2}}, 0x2e)

program did not crash
testing program (duration=30.642292512s, {Threaded:true Repeat:true RepeatTimes:0 Procs:5 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:false Wifi:false IEEE802154:false Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): socket$pppl2tp-socket$inet6_udp-ioctl$XFS_IOC_START_COMMIT
detailed listing:
executing program 0:
r0 = socket$pppl2tp(0x18, 0x1, 0x1)
socket$inet6_udp(0xa, 0x2, 0x0)
ioctl$XFS_IOC_START_COMMIT(r0, 0x80585882, 0x0)

program did not crash
testing program (duration=30.642292512s, {Threaded:true Repeat:true RepeatTimes:0 Procs:5 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:false Wifi:false IEEE802154:false Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): socket$pppl2tp-connect$pppl2tp-ioctl$XFS_IOC_START_COMMIT
detailed listing:
executing program 0:
r0 = socket$pppl2tp(0x18, 0x1, 0x1)
connect$pppl2tp(r0, &(0x7f0000000000)=@pppol2tpv3={0x18, 0x1, {0x3, 0xffffffffffffffff, {0x2, 0x0, @dev}, 0x2}}, 0x2e)
ioctl$XFS_IOC_START_COMMIT(r0, 0x80585882, 0x0)

program did not crash
testing program (duration=30.642292512s, {Threaded:true Repeat:true RepeatTimes:0 Procs:5 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:false Wifi:false IEEE802154:false Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): socket$inet6_udp-connect$pppl2tp-ioctl$XFS_IOC_START_COMMIT
detailed listing:
executing program 0:
r0 = socket$inet6_udp(0xa, 0x2, 0x0)
connect$pppl2tp(0xffffffffffffffff, &(0x7f0000000000)=@pppol2tpv3={0x18, 0x1, {0x3, r0, {0x2, 0x0, @dev}, 0x2}}, 0x2e)
ioctl$XFS_IOC_START_COMMIT(0xffffffffffffffff, 0x80585882, 0x0)

program did not crash
testing program (duration=30.642292512s, {Threaded:true Repeat:true RepeatTimes:0 Procs:5 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:false Wifi:false IEEE802154:false Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): socket$pppl2tp-socket$inet6_udp-connect$pppl2tp-ioctl$XFS_IOC_START_COMMIT
detailed listing:
executing program 0:
r0 = socket$pppl2tp(0x18, 0x1, 0x1)
socket$inet6_udp(0xa, 0x2, 0x0)
connect$pppl2tp(r0, 0x0, 0x0)
ioctl$XFS_IOC_START_COMMIT(r0, 0x80585882, 0x0)

program did not crash
extracting C reproducer
testing compiled C program (duration=30.642292512s, {Threaded:true Repeat:true RepeatTimes:0 Procs:5 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:false Wifi:false IEEE802154:false Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): socket$pppl2tp-socket$inet6_udp-connect$pppl2tp-ioctl$XFS_IOC_START_COMMIT
program crashed: KASAN: use-after-free Write in pppol2tp_release
simplifying C reproducer
testing compiled C program (duration=30.642292512s, {Threaded:false Repeat:true RepeatTimes:0 Procs:5 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:false Wifi:false IEEE802154:false Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): socket$pppl2tp-socket$inet6_udp-connect$pppl2tp-ioctl$XFS_IOC_START_COMMIT
program crashed: KASAN: use-after-free Write in pppol2tp_release
testing compiled C program (duration=30.642292512s, {Threaded:false Repeat:false RepeatTimes:0 Procs:1 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:false Cgroups:false BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:false Wifi:false IEEE802154:false Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): socket$pppl2tp-socket$inet6_udp-connect$pppl2tp-ioctl$XFS_IOC_START_COMMIT
program crashed: KASAN: use-after-free Write in pppol2tp_release
testing compiled C program (duration=30.642292512s, {Threaded:false Repeat:false RepeatTimes:0 Procs:1 Slowdown:1 Sandbox: SandboxArg:0 Leak:false NetInjection:false NetDevices:false NetReset:false Cgroups:false BinfmtMisc:false CloseFDs:false KCSAN:false DevlinkPCI:false NicVF:false USB:false VhciInjection:false Wifi:false IEEE802154:false Sysctl:true Swap:false UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): socket$pppl2tp-socket$inet6_udp-connect$pppl2tp-ioctl$XFS_IOC_START_COMMIT
program crashed: KASAN: use-after-free Write in pppol2tp_release
testing compiled C program (duration=30.642292512s, {Threaded:false Repeat:false RepeatTimes:0 Procs:1 Slowdown:1 Sandbox: SandboxArg:0 Leak:false NetInjection:false NetDevices:false NetReset:false Cgroups:false BinfmtMisc:false CloseFDs:false KCSAN:false DevlinkPCI:false NicVF:false USB:false VhciInjection:false Wifi:false IEEE802154:false Sysctl:true Swap:false UseTmpDir:false HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): socket$pppl2tp-socket$inet6_udp-connect$pppl2tp-ioctl$XFS_IOC_START_COMMIT
program crashed: KASAN: use-after-free Read in pppol2tp_sock_to_session
a never seen crash title: KASAN: use-after-free Read in pppol2tp_sock_to_session, ignore
testing compiled C program (duration=30.642292512s, {Threaded:false Repeat:false RepeatTimes:0 Procs:1 Slowdown:1 Sandbox: SandboxArg:0 Leak:false NetInjection:false NetDevices:false NetReset:false Cgroups:false BinfmtMisc:false CloseFDs:false KCSAN:false DevlinkPCI:false NicVF:false USB:false VhciInjection:false Wifi:false IEEE802154:false Sysctl:true Swap:false UseTmpDir:true HandleSegv:false Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): socket$pppl2tp-socket$inet6_udp-connect$pppl2tp-ioctl$XFS_IOC_START_COMMIT
program crashed: KASAN: use-after-free Read in pppol2tp_sock_to_session
a never seen crash title: KASAN: use-after-free Read in pppol2tp_sock_to_session, ignore
testing compiled C program (duration=30.642292512s, {Threaded:false Repeat:false RepeatTimes:0 Procs:1 Slowdown:1 Sandbox: SandboxArg:0 Leak:false NetInjection:false NetDevices:false NetReset:false Cgroups:false BinfmtMisc:false CloseFDs:false KCSAN:false DevlinkPCI:false NicVF:false USB:false VhciInjection:false Wifi:false IEEE802154:false Sysctl:false Swap:false UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): socket$pppl2tp-socket$inet6_udp-connect$pppl2tp-ioctl$XFS_IOC_START_COMMIT
program crashed: KASAN: use-after-free Read in pppol2tp_sock_to_session
a never seen crash title: KASAN: use-after-free Read in pppol2tp_sock_to_session, ignore
testing program (duration=30.642292512s, {Threaded:false Repeat:false RepeatTimes:0 Procs:1 Slowdown:1 Sandbox: SandboxArg:0 Leak:false NetInjection:false NetDevices:false NetReset:false Cgroups:false BinfmtMisc:false CloseFDs:false KCSAN:false DevlinkPCI:false NicVF:false USB:false VhciInjection:false Wifi:false IEEE802154:false Sysctl:true Swap:false UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): socket$pppl2tp-socket$inet6_udp-connect$pppl2tp-ioctl$XFS_IOC_START_COMMIT
detailed listing:
executing program 0:
r0 = socket$pppl2tp(0x18, 0x1, 0x1)
r1 = socket$inet6_udp(0xa, 0x2, 0x0)
connect$pppl2tp(r0, &(0x7f0000000000)=@pppol2tpv3={0x18, 0x1, {0x3, r1, {0x2, 0x0, @dev}, 0x2}}, 0x2e)
ioctl$XFS_IOC_START_COMMIT(r0, 0x80585882, 0x0)

program crashed: KASAN: use-after-free Write in pppol2tp_release
validation run: crashed=true
testing program (duration=30.642292512s, {Threaded:false Repeat:false RepeatTimes:0 Procs:1 Slowdown:1 Sandbox: SandboxArg:0 Leak:false NetInjection:false NetDevices:false NetReset:false Cgroups:false BinfmtMisc:false CloseFDs:false KCSAN:false DevlinkPCI:false NicVF:false USB:false VhciInjection:false Wifi:false IEEE802154:false Sysctl:true Swap:false UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): socket$pppl2tp-socket$inet6_udp-connect$pppl2tp-ioctl$XFS_IOC_START_COMMIT
detailed listing:
executing program 0:
r0 = socket$pppl2tp(0x18, 0x1, 0x1)
r1 = socket$inet6_udp(0xa, 0x2, 0x0)
connect$pppl2tp(r0, &(0x7f0000000000)=@pppol2tpv3={0x18, 0x1, {0x3, r1, {0x2, 0x0, @dev}, 0x2}}, 0x2e)
ioctl$XFS_IOC_START_COMMIT(r0, 0x80585882, 0x0)

program crashed: KASAN: use-after-free Write in pppol2tp_release
validation run: crashed=true
testing program (duration=30.642292512s, {Threaded:false Repeat:false RepeatTimes:0 Procs:1 Slowdown:1 Sandbox: SandboxArg:0 Leak:false NetInjection:false NetDevices:false NetReset:false Cgroups:false BinfmtMisc:false CloseFDs:false KCSAN:false DevlinkPCI:false NicVF:false USB:false VhciInjection:false Wifi:false IEEE802154:false Sysctl:true Swap:false UseTmpDir:true HandleSegv:true Trace:false CallComments:true LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): socket$pppl2tp-socket$inet6_udp-connect$pppl2tp-ioctl$XFS_IOC_START_COMMIT
detailed listing:
executing program 0:
r0 = socket$pppl2tp(0x18, 0x1, 0x1)
r1 = socket$inet6_udp(0xa, 0x2, 0x0)
connect$pppl2tp(r0, &(0x7f0000000000)=@pppol2tpv3={0x18, 0x1, {0x3, r1, {0x2, 0x0, @dev}, 0x2}}, 0x2e)
ioctl$XFS_IOC_START_COMMIT(r0, 0x80585882, 0x0)

program crashed: KASAN: use-after-free Write in pppol2tp_release
validation run: crashed=true
reproducing took 10m20.209329778s
repro crashed as (corrupted=false):
==================================================================
BUG: KASAN: use-after-free in instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
BUG: KASAN: use-after-free in atomic64_try_cmpxchg_acquire include/asm-generic/atomic-instrumented.h:1515 [inline]
BUG: KASAN: use-after-free in atomic_long_try_cmpxchg_acquire include/asm-generic/atomic-long.h:443 [inline]
BUG: KASAN: use-after-free in __mutex_trylock_fast kernel/locking/mutex.c:173 [inline]
BUG: KASAN: use-after-free in mutex_lock+0x85/0xf0 kernel/locking/mutex.c:298
Write of size 8 at addr ffff88810b0cfd50 by task syz.2.17/385

CPU: 1 PID: 385 Comm: syz.2.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
 __dump_stack+0x21/0x24 lib/dump_stack.c:77
 dump_stack_lvl+0x1a7/0x208 lib/dump_stack.c:118
 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:435 [inline]
 kasan_report+0x100/0x140 mm/kasan/report.c:452
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x249/0x2a0 mm/kasan/generic.c:189
 __kasan_check_write+0x14/0x20 mm/kasan/shadow.c:37
 instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
 atomic64_try_cmpxchg_acquire include/asm-generic/atomic-instrumented.h:1515 [inline]
 atomic_long_try_cmpxchg_acquire include/asm-generic/atomic-long.h:443 [inline]
 __mutex_trylock_fast kernel/locking/mutex.c:173 [inline]
 mutex_lock+0x85/0xf0 kernel/locking/mutex.c:298
 pppol2tp_release+0x178/0x2b0 net/l2tp/l2tp_ppp.c:442
 __sock_release net/socket.c:597 [inline]
 sock_close+0xb8/0x200 net/socket.c:1286
 __fput+0x2dc/0x730 fs/file_table.c:281
 ____fput+0x15/0x20 fs/file_table.c:314
 task_work_run+0x127/0x190 kernel/task_work.c:189
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_user_mode_loop+0xcb/0xe0 kernel/entry/common.c:172
 exit_to_user_mode_prepare+0x76/0xa0 kernel/entry/common.c:199
 syscall_exit_to_user_mode+0x1d/0x40 kernel/entry/common.c:274
 do_syscall_64+0x3d/0x40 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7fe1c6c5ae59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe8ab8e228 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007ffe8ab8e310 RCX: 00007fe1c6c5ae59
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 0000000000005a7c R08: 0000000000000001 R09: 0000000000000000
R10: 0000001b32c20000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fe1c6ed3fac R14: 00007fe1c6ed3fa8 R15: 00007fe1c6ed3fa0

Allocated by task 385:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:45 [inline]
 set_alloc_info mm/kasan/common.c:430 [inline]
 ____kasan_kmalloc mm/kasan/common.c:509 [inline]
 __kasan_kmalloc+0xd4/0x100 mm/kasan/common.c:518
 kasan_kmalloc include/linux/kasan.h:254 [inline]
 __kmalloc+0x19f/0x330 mm/slub.c:4038
 kmalloc include/linux/slab.h:560 [inline]
 kzalloc include/linux/slab.h:667 [inline]
 l2tp_session_create+0x39/0xb60 net/l2tp/l2tp_core.c:1616
 pppol2tp_connect+0xbf5/0x1640 net/l2tp/l2tp_ppp.c:772
 __sys_connect_file net/socket.c:1866 [inline]
 __sys_connect+0x3ce/0x450 net/socket.c:1883
 __do_sys_connect net/socket.c:1893 [inline]
 __se_sys_connect net/socket.c:1890 [inline]
 __x64_sys_connect+0x7a/0x90 net/socket.c:1890
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

Freed by task 385:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4a/0x70 mm/kasan/common.c:45
 kasan_set_free_info+0x23/0x40 mm/kasan/generic.c:370
 ____kasan_slab_free+0x125/0x160 mm/kasan/common.c:362
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:370
 kasan_slab_free include/linux/kasan.h:220 [inline]
 slab_free_hook mm/slub.c:1600 [inline]
 slab_free_freelist_hook+0xc5/0x190 mm/slub.c:1626
 slab_free mm/slub.c:3208 [inline]
 kfree+0xc0/0x270 mm/slub.c:4196
 l2tp_session_free net/l2tp/l2tp_core.c:168 [inline]
 l2tp_session_put+0xb2/0x1a0 net/l2tp/l2tp_core.c:193
 l2tp_session_delete+0x3a9/0x4a0 net/l2tp/l2tp_core.c:1589
 pppol2tp_release+0x169/0x2b0 net/l2tp/l2tp_ppp.c:439
 __sock_release net/socket.c:597 [inline]
 sock_close+0xb8/0x200 net/socket.c:1286
 __fput+0x2dc/0x730 fs/file_table.c:281
 ____fput+0x15/0x20 fs/file_table.c:314
 task_work_run+0x127/0x190 kernel/task_work.c:189
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_user_mode_loop+0xcb/0xe0 kernel/entry/common.c:172
 exit_to_user_mode_prepare+0x76/0xa0 kernel/entry/common.c:199
 syscall_exit_to_user_mode+0x1d/0x40 kernel/entry/common.c:274
 do_syscall_64+0x3d/0x40 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

The buggy address belongs to the object at ffff88810b0cfc00
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 336 bytes inside of
 512-byte region [ffff88810b0cfc00, ffff88810b0cfe00)
The buggy address belongs to the page:
page:ffffea00042c3300 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10b0cc
head:ffffea00042c3300 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 dead000000000100 dead000000000122 ffff888100043080
raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0x152a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_HARDWALL), pid 365, ts 23181141276, free_ts 23171315381
 set_page_owner include/linux/page_owner.h:35 [inline]
 post_alloc_hook mm/page_alloc.c:2456 [inline]
 prep_new_page+0x176/0x190 mm/page_alloc.c:2462
 get_page_from_freelist+0x225f/0x23f0 mm/page_alloc.c:4254
 __alloc_pages_nodemask+0x29a/0x640 mm/page_alloc.c:5384
 alloc_slab_page mm/slub.c:-1 [inline]
 allocate_slab mm/slub.c:1813 [inline]
 new_slab+0x84/0x3f0 mm/slub.c:1874
 new_slab_objects mm/slub.c:2632 [inline]
 ___slab_alloc+0x2f8/0x4c0 mm/slub.c:2796
 __slab_alloc+0x63/0xa0 mm/slub.c:2836
 slab_alloc_node mm/slub.c:2918 [inline]
 slab_alloc mm/slub.c:2960 [inline]
 __kmalloc+0x1f9/0x330 mm/slub.c:4034
 kmalloc include/linux/slab.h:560 [inline]
 kzalloc include/linux/slab.h:667 [inline]
 neigh_alloc net/core/neighbour.c:439 [inline]
 ___neigh_create+0x6ec/0x1a70 net/core/neighbour.c:592
 __neigh_create+0x31/0x40 net/core/neighbour.c:680
 ip6_finish_output2+0x8fe/0x1540 net/ipv6/ip6_output.c:127
 __ip6_finish_output+0x5fd/0x790 net/ipv6/ip6_output.c:201
 ip6_finish_output+0x33/0x1e0 net/ipv6/ip6_output.c:211
 NF_HOOK_COND include/linux/netfilter.h:288 [inline]
 ip6_output+0x1fa/0x420 net/ipv6/ip6_output.c:234
 dst_output include/net/dst.h:451 [inline]
 NF_HOOK include/linux/netfilter.h:299 [inline]
 mld_sendpack+0x61e/0xb00 net/ipv6/mcast.c:1676
 mld_send_cr net/ipv6/mcast.c:1972 [inline]
 mld_ifc_timer_expire+0x862/0xc60 net/ipv6/mcast.c:2471
 call_timer_fn+0x38/0x290 kernel/time/timer.c:1450
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:28 [inline]
 free_pages_prepare mm/page_alloc.c:1349 [inline]
 __free_pages_ok+0x80b/0x830 mm/page_alloc.c:1629
 free_the_page mm/page_alloc.c:5445 [inline]
 __free_pages+0xd8/0x390 mm/page_alloc.c:5454
 kfree+0x1e4/0x270 mm/slub.c:4193
 kvfree+0x35/0x40 mm/util.c:647
 wg_destruct+0x2bf/0x300 drivers/net/wireguard/device.c:250
 netdev_run_todo+0xb5e/0xda0 net/core/dev.c:10354
 rtnl_unlock+0xe/0x10 net/core/rtnetlink.c:112
 default_device_exit_batch+0x363/0x3c0 net/core/dev.c:11301
 ops_exit_list net/core/net_namespace.c:190 [inline]
 cleanup_net+0x5fe/0xb80 net/core/net_namespace.c:609
 process_one_work+0x6fd/0xbc0 kernel/workqueue.c:2301
 worker_thread+0xa8e/0x13c0 kernel/workqueue.c:2447
 kthread+0x324/0x3b0 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298

Memory state around the buggy address:
 ffff88810b0cfc00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88810b0cfc80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88810b0cfd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                 ^
 ffff88810b0cfd80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88810b0cfe00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

final repro crashed as (corrupted=false):
==================================================================
BUG: KASAN: use-after-free in instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
BUG: KASAN: use-after-free in atomic64_try_cmpxchg_acquire include/asm-generic/atomic-instrumented.h:1515 [inline]
BUG: KASAN: use-after-free in atomic_long_try_cmpxchg_acquire include/asm-generic/atomic-long.h:443 [inline]
BUG: KASAN: use-after-free in __mutex_trylock_fast kernel/locking/mutex.c:173 [inline]
BUG: KASAN: use-after-free in mutex_lock+0x85/0xf0 kernel/locking/mutex.c:298
Write of size 8 at addr ffff88810b0cfd50 by task syz.2.17/385

CPU: 1 PID: 385 Comm: syz.2.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
 __dump_stack+0x21/0x24 lib/dump_stack.c:77
 dump_stack_lvl+0x1a7/0x208 lib/dump_stack.c:118
 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:435 [inline]
 kasan_report+0x100/0x140 mm/kasan/report.c:452
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x249/0x2a0 mm/kasan/generic.c:189
 __kasan_check_write+0x14/0x20 mm/kasan/shadow.c:37
 instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
 atomic64_try_cmpxchg_acquire include/asm-generic/atomic-instrumented.h:1515 [inline]
 atomic_long_try_cmpxchg_acquire include/asm-generic/atomic-long.h:443 [inline]
 __mutex_trylock_fast kernel/locking/mutex.c:173 [inline]
 mutex_lock+0x85/0xf0 kernel/locking/mutex.c:298
 pppol2tp_release+0x178/0x2b0 net/l2tp/l2tp_ppp.c:442
 __sock_release net/socket.c:597 [inline]
 sock_close+0xb8/0x200 net/socket.c:1286
 __fput+0x2dc/0x730 fs/file_table.c:281
 ____fput+0x15/0x20 fs/file_table.c:314
 task_work_run+0x127/0x190 kernel/task_work.c:189
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_user_mode_loop+0xcb/0xe0 kernel/entry/common.c:172
 exit_to_user_mode_prepare+0x76/0xa0 kernel/entry/common.c:199
 syscall_exit_to_user_mode+0x1d/0x40 kernel/entry/common.c:274
 do_syscall_64+0x3d/0x40 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7fe1c6c5ae59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe8ab8e228 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007ffe8ab8e310 RCX: 00007fe1c6c5ae59
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 0000000000005a7c R08: 0000000000000001 R09: 0000000000000000
R10: 0000001b32c20000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fe1c6ed3fac R14: 00007fe1c6ed3fa8 R15: 00007fe1c6ed3fa0

Allocated by task 385:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:45 [inline]
 set_alloc_info mm/kasan/common.c:430 [inline]
 ____kasan_kmalloc mm/kasan/common.c:509 [inline]
 __kasan_kmalloc+0xd4/0x100 mm/kasan/common.c:518
 kasan_kmalloc include/linux/kasan.h:254 [inline]
 __kmalloc+0x19f/0x330 mm/slub.c:4038
 kmalloc include/linux/slab.h:560 [inline]
 kzalloc include/linux/slab.h:667 [inline]
 l2tp_session_create+0x39/0xb60 net/l2tp/l2tp_core.c:1616
 pppol2tp_connect+0xbf5/0x1640 net/l2tp/l2tp_ppp.c:772
 __sys_connect_file net/socket.c:1866 [inline]
 __sys_connect+0x3ce/0x450 net/socket.c:1883
 __do_sys_connect net/socket.c:1893 [inline]
 __se_sys_connect net/socket.c:1890 [inline]
 __x64_sys_connect+0x7a/0x90 net/socket.c:1890
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

Freed by task 385:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4a/0x70 mm/kasan/common.c:45
 kasan_set_free_info+0x23/0x40 mm/kasan/generic.c:370
 ____kasan_slab_free+0x125/0x160 mm/kasan/common.c:362
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:370
 kasan_slab_free include/linux/kasan.h:220 [inline]
 slab_free_hook mm/slub.c:1600 [inline]
 slab_free_freelist_hook+0xc5/0x190 mm/slub.c:1626
 slab_free mm/slub.c:3208 [inline]
 kfree+0xc0/0x270 mm/slub.c:4196
 l2tp_session_free net/l2tp/l2tp_core.c:168 [inline]
 l2tp_session_put+0xb2/0x1a0 net/l2tp/l2tp_core.c:193
 l2tp_session_delete+0x3a9/0x4a0 net/l2tp/l2tp_core.c:1589
 pppol2tp_release+0x169/0x2b0 net/l2tp/l2tp_ppp.c:439
 __sock_release net/socket.c:597 [inline]
 sock_close+0xb8/0x200 net/socket.c:1286
 __fput+0x2dc/0x730 fs/file_table.c:281
 ____fput+0x15/0x20 fs/file_table.c:314
 task_work_run+0x127/0x190 kernel/task_work.c:189
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_user_mode_loop+0xcb/0xe0 kernel/entry/common.c:172
 exit_to_user_mode_prepare+0x76/0xa0 kernel/entry/common.c:199
 syscall_exit_to_user_mode+0x1d/0x40 kernel/entry/common.c:274
 do_syscall_64+0x3d/0x40 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

The buggy address belongs to the object at ffff88810b0cfc00
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 336 bytes inside of
 512-byte region [ffff88810b0cfc00, ffff88810b0cfe00)
The buggy address belongs to the page:
page:ffffea00042c3300 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10b0cc
head:ffffea00042c3300 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 dead000000000100 dead000000000122 ffff888100043080
raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0x152a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_HARDWALL), pid 365, ts 23181141276, free_ts 23171315381
 set_page_owner include/linux/page_owner.h:35 [inline]
 post_alloc_hook mm/page_alloc.c:2456 [inline]
 prep_new_page+0x176/0x190 mm/page_alloc.c:2462
 get_page_from_freelist+0x225f/0x23f0 mm/page_alloc.c:4254
 __alloc_pages_nodemask+0x29a/0x640 mm/page_alloc.c:5384
 alloc_slab_page mm/slub.c:-1 [inline]
 allocate_slab mm/slub.c:1813 [inline]
 new_slab+0x84/0x3f0 mm/slub.c:1874
 new_slab_objects mm/slub.c:2632 [inline]
 ___slab_alloc+0x2f8/0x4c0 mm/slub.c:2796
 __slab_alloc+0x63/0xa0 mm/slub.c:2836
 slab_alloc_node mm/slub.c:2918 [inline]
 slab_alloc mm/slub.c:2960 [inline]
 __kmalloc+0x1f9/0x330 mm/slub.c:4034
 kmalloc include/linux/slab.h:560 [inline]
 kzalloc include/linux/slab.h:667 [inline]
 neigh_alloc net/core/neighbour.c:439 [inline]
 ___neigh_create+0x6ec/0x1a70 net/core/neighbour.c:592
 __neigh_create+0x31/0x40 net/core/neighbour.c:680
 ip6_finish_output2+0x8fe/0x1540 net/ipv6/ip6_output.c:127
 __ip6_finish_output+0x5fd/0x790 net/ipv6/ip6_output.c:201
 ip6_finish_output+0x33/0x1e0 net/ipv6/ip6_output.c:211
 NF_HOOK_COND include/linux/netfilter.h:288 [inline]
 ip6_output+0x1fa/0x420 net/ipv6/ip6_output.c:234
 dst_output include/net/dst.h:451 [inline]
 NF_HOOK include/linux/netfilter.h:299 [inline]
 mld_sendpack+0x61e/0xb00 net/ipv6/mcast.c:1676
 mld_send_cr net/ipv6/mcast.c:1972 [inline]
 mld_ifc_timer_expire+0x862/0xc60 net/ipv6/mcast.c:2471
 call_timer_fn+0x38/0x290 kernel/time/timer.c:1450
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:28 [inline]
 free_pages_prepare mm/page_alloc.c:1349 [inline]
 __free_pages_ok+0x80b/0x830 mm/page_alloc.c:1629
 free_the_page mm/page_alloc.c:5445 [inline]
 __free_pages+0xd8/0x390 mm/page_alloc.c:5454
 kfree+0x1e4/0x270 mm/slub.c:4193
 kvfree+0x35/0x40 mm/util.c:647
 wg_destruct+0x2bf/0x300 drivers/net/wireguard/device.c:250
 netdev_run_todo+0xb5e/0xda0 net/core/dev.c:10354
 rtnl_unlock+0xe/0x10 net/core/rtnetlink.c:112
 default_device_exit_batch+0x363/0x3c0 net/core/dev.c:11301
 ops_exit_list net/core/net_namespace.c:190 [inline]
 cleanup_net+0x5fe/0xb80 net/core/net_namespace.c:609
 process_one_work+0x6fd/0xbc0 kernel/workqueue.c:2301
 worker_thread+0xa8e/0x13c0 kernel/workqueue.c:2447
 kthread+0x324/0x3b0 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298

Memory state around the buggy address:
 ffff88810b0cfc00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88810b0cfc80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88810b0cfd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                 ^
 ffff88810b0cfd80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88810b0cfe00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================