KASAN: use-after-free Write in __ip6_del

Kernel	Title	Rank 🛈	Repro	Fix bisect	Count	Last	Reported	Patched	Status
android-5-10	KASAN: use-after-free Write in __ip6_del_rt	22	syz		11	329d	479d	0/2	auto-obsoleted due to no activity on 2025/12/18 13:03
android-6-1	KASAN: use-after-free Write in __ip6_del_rt origin:lts	22	syz	error	1	290d	290d	0/2	auto-obsoleted due to no activity on 2026/01/26 10:27
linux-5.15	KASAN: use-after-free Read in __ip6_del_rt	19			1	504d	504d	0/3	auto-obsoleted due to no activity on 2025/07/06 21:22
linux-6.6	KASAN: slab-use-after-free Read in __ip6_del_rt	19			1	360d	360d	0/2	auto-obsoleted due to no activity on 2025/11/27 23:21

================================================================== BUG: KASAN: use-after-free in instrument_atomic_read_write include/linux/instrumented.h:101 [inline] BUG: KASAN: use-after-free in atomic_try_cmpxchg_acquire include/linux/atomic/atomic-instrumented.h:511 [inline] BUG: KASAN: use-after-free in queued_spin_lock include/asm-generic/qspinlock.h:82 [inline] BUG: KASAN: use-after-free in do_raw_spin_lock include/linux/spinlock.h:187 [inline] BUG: KASAN: use-after-free in __raw_spin_lock_bh include/linux/spinlock_api_smp.h:136 [inline] BUG: KASAN: use-after-free in _raw_spin_lock_bh+0x81/0xe0 kernel/locking/spinlock.c:178 Write of size 4 at addr ffff88810b71c914 by task kworker/u4:45/10518 CPU: 1 PID: 10518 Comm: kworker/u4:45 Tainted: G W 5.15.180-syzkaller-00024-g88c4075c39ed #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025 Workqueue: netns cleanup_net Call Trace: <TASK> __dump_stack+0x21/0x30 lib/dump_stack.c:88 dump_stack_lvl+0xee/0x150 lib/dump_stack.c:106 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248 __kasan_report mm/kasan/report.c:427 [inline] kasan_report+0xf1/0x140 mm/kasan/report.c:444 check_region_inline mm/kasan/generic.c:-1 [inline] kasan_check_range+0x280/0x290 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] atomic_try_cmpxchg_acquire include/linux/atomic/atomic-instrumented.h:511 [inline] queued_spin_lock include/asm-generic/qspinlock.h:82 [inline] do_raw_spin_lock include/linux/spinlock.h:187 [inline] __raw_spin_lock_bh include/linux/spinlock_api_smp.h:136 [inline] _raw_spin_lock_bh+0x81/0xe0 kernel/locking/spinlock.c:178 spin_lock_bh include/linux/spinlock.h:368 [inline] __ip6_del_rt+0x8f/0x150 net/ipv6/route.c:3902 ip6_del_rt+0xb0/0xf0 net/ipv6/route.c:3918 __remove_nexthop_fib+0x1e9/0x260 net/ipv4/nexthop.c:1860 __remove_nexthop net/ipv4/nexthop.c:1868 [inline] remove_nexthop+0x73/0x500 net/ipv4/nexthop.c:1894 remove_nh_grp_entry net/ipv4/nexthop.c:1750 [inline] remove_nexthop_from_groups+0x231/0x1210 net/ipv4/nexthop.c:1815 __remove_nexthop net/ipv4/nexthop.c:1879 [inline] remove_nexthop+0x3b6/0x500 net/ipv4/nexthop.c:1894 flush_all_nexthops net/ipv4/nexthop.c:2405 [inline] nexthop_net_exit+0x3a/0xa0 net/ipv4/nexthop.c:3728 ops_exit_list net/core/net_namespace.c:172 [inline] cleanup_net+0x58b/0xad0 net/core/net_namespace.c:599 process_one_work+0x6be/0xba0 kernel/workqueue.c:2325 worker_thread+0xa59/0x1200 kernel/workqueue.c:2472 kthread+0x411/0x500 kernel/kthread.c:337 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287 </TASK> Allocated by task 275: 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:433 [inline] ____kasan_kmalloc mm/kasan/common.c:512 [inline] __kasan_kmalloc+0xda/0x110 mm/kasan/common.c:521 kasan_kmalloc include/linux/kasan.h:227 [inline] kmem_cache_alloc_trace+0x119/0x270 mm/slub.c:3269 kmalloc include/linux/slab.h:616 [inline] kzalloc include/linux/slab.h:747 [inline] fib6_net_init+0x23d/0x8c0 net/ipv6/ip6_fib.c:2382 ops_init+0x1ba/0x4a0 net/core/net_namespace.c:138 setup_net+0x344/0xa90 net/core/net_namespace.c:332 copy_net_ns+0x355/0x5c0 net/core/net_namespace.c:476 create_new_namespaces+0x3a2/0x660 kernel/nsproxy.c:110 unshare_nsproxy_namespaces+0x120/0x170 kernel/nsproxy.c:226 ksys_unshare+0x4ac/0x7b0 kernel/fork.c:3166 __do_sys_unshare kernel/fork.c:3240 [inline] __se_sys_unshare kernel/fork.c:3238 [inline] __x64_sys_unshare+0x38/0x40 kernel/fork.c:3238 x64_sys_call+0x442/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:273 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x66/0xd0 Freed by task 10518: 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:365 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:373 kasan_slab_free include/linux/kasan.h:193 [inline] slab_free_hook mm/slub.c:1723 [inline] slab_free_freelist_hook+0xc2/0x190 mm/slub.c:1749 slab_free mm/slub.c:3521 [inline] kfree+0xc4/0x270 mm/slub.c:4583 fib6_free_table net/ipv6/ip6_fib.c:215 [inline] fib6_net_exit+0x270/0x300 net/ipv6/ip6_fib.c:2436 ops_exit_list net/core/net_namespace.c:172 [inline] cleanup_net+0x58b/0xad0 net/core/net_namespace.c:599 process_one_work+0x6be/0xba0 kernel/workqueue.c:2325 worker_thread+0xa59/0x1200 kernel/workqueue.c:2472 kthread+0x411/0x500 kernel/kthread.c:337 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287 The buggy address belongs to the object at ffff88810b71c900 which belongs to the cache kmalloc-128 of size 128 The buggy address is located 20 bytes inside of 128-byte region [ffff88810b71c900, ffff88810b71c980) The buggy address belongs to the page: page:ffffea00042dc700 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10b71c flags: 0x4000000000000200(slab|zone=1) raw: 4000000000000200 ffffea00041cf340 0000000b0000000b ffff888100042a80 raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected page_owner tracks the page as allocated page last allocated via order 0, migratetype Unmovable, gfp_mask 0x12cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY), pid 1, ts 3631385796, free_ts 0 set_page_owner include/linux/page_owner.h:33 [inline] post_alloc_hook+0x192/0x1b0 mm/page_alloc.c:2605 prep_new_page+0x1c/0x110 mm/page_alloc.c:2611 get_page_from_freelist+0x2cc5/0x2d50 mm/page_alloc.c:4485 __alloc_pages+0x18f/0x440 mm/page_alloc.c:5781 alloc_slab_page mm/slub.c:-1 [inline] allocate_slab mm/slub.c:1932 [inline] new_slab+0xa1/0x4d0 mm/slub.c:1995 ___slab_alloc+0x381/0x810 mm/slub.c:3028 __slab_alloc+0x49/0x90 mm/slub.c:3115 slab_alloc_node mm/slub.c:3206 [inline] slab_alloc mm/slub.c:3250 [inline] kmem_cache_alloc_trace+0x146/0x270 mm/slub.c:3267 kmalloc include/linux/slab.h:616 [inline] kzalloc include/linux/slab.h:747 [inline] call_usermodehelper_setup+0x8e/0x210 kernel/umh.c:365 kobject_uevent_env+0x639/0x700 lib/kobject_uevent.c:629 kobject_uevent+0x1d/0x30 lib/kobject_uevent.c:657 driver_bound+0x453/0x4a0 drivers/base/dd.c:400 really_probe+0x777/0x970 drivers/base/dd.c:649 __driver_probe_device+0x198/0x280 drivers/base/dd.c:755 driver_probe_device+0x54/0x3e0 drivers/base/dd.c:785 __device_attach_driver+0x2a6/0x460 drivers/base/dd.c:907 page_owner free stack trace missing Memory state around the buggy address: ffff88810b71c800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88810b71c880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff88810b71c900: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88810b71c980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88810b71ca00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 fc fc 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