* [syzbot] [net?] KASAN: slab-use-after-free Read in fib_rules_lookup
@ 2026-06-16 14:05 syzbot
2026-06-16 15:31 ` Ido Schimmel
0 siblings, 1 reply; 5+ messages in thread
From: syzbot @ 2026-06-16 14:05 UTC (permalink / raw)
To: davem, dsahern, edumazet, horms, idosch, kuba, linux-kernel,
netdev, pabeni, syzkaller-bugs
Hello,
syzbot found the following issue on:
HEAD commit: 72dfa4700f78 net: dsa: sja1105: fix lastused timestamp in ..
git tree: net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=15794bd2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=a0842261b62cdea8
dashboard link: https://syzkaller.appspot.com/bug?extid=965506b59a2de0b6905c
compiler: Debian clang version 22.1.6 (++20260514074242+fc4aad7b5db3-1~exp1~20260514074407.73), Debian LLD 22.1.6
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/d4e16f50a97c/disk-72dfa470.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6cd4a736e796/vmlinux-72dfa470.xz
kernel image: https://storage.googleapis.com/syzbot-assets/548b0011c8e8/bzImage-72dfa470.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+965506b59a2de0b6905c@syzkaller.appspotmail.com
bond0 (unregistering): Released all slaves
bond1 (unregistering): Released all slaves
bond2 (unregistering): (slave dummy0): Releasing active interface
bond2 (unregistering): Released all slaves
==================================================================
BUG: KASAN: slab-use-after-free in fib_rules_lookup+0x15e/0xeb0 net/core/fib_rules.c:321
Read of size 8 at addr ffff88804ec4c680 by task kworker/u8:21/12641
CPU: 0 UID: 0 PID: 12641 Comm: kworker/u8:21 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Workqueue: netns cleanup_net
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_address_description+0x55/0x1e0 mm/kasan/report.c:378
print_report+0x58/0x70 mm/kasan/report.c:482
kasan_report+0x117/0x150 mm/kasan/report.c:595
fib_rules_lookup+0x15e/0xeb0 net/core/fib_rules.c:321
__fib_lookup+0x106/0x210 net/ipv4/fib_rules.c:96
ip_route_output_key_hash_rcu+0x294/0x2720 net/ipv4/route.c:2811
ip_route_output_key_hash+0x18d/0x2a0 net/ipv4/route.c:2702
__ip_route_output_key include/net/route.h:169 [inline]
ip_route_output_flow+0x2a/0x150 net/ipv4/route.c:2929
ip4_datagram_release_cb+0x89d/0xbe0 net/ipv4/datagram.c:118
release_sock+0x206/0x260 net/core/sock.c:3861
inet_shutdown+0x2b1/0x390 net/ipv4/af_inet.c:950
udp_tunnel_sock_release+0x6d/0x80 net/ipv4/udp_tunnel_core.c:197
fou_release net/ipv4/fou_core.c:562 [inline]
fou_exit_net+0x17d/0x1f0 net/ipv4/fou_core.c:1230
ops_exit_list net/core/net_namespace.c:199 [inline]
ops_undo_list+0x43d/0x8d0 net/core/net_namespace.c:252
cleanup_net+0x572/0x810 net/core/net_namespace.c:702
process_one_work kernel/workqueue.c:3314 [inline]
process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3397
worker_thread+0xa47/0xfb0 kernel/workqueue.c:3478
kthread+0x389/0x470 kernel/kthread.c:436
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
Allocated by task 19121:
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
__kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415
kasan_kmalloc include/linux/kasan.h:263 [inline]
__do_kmalloc_node mm/slub.c:5296 [inline]
__kmalloc_node_track_caller_noprof+0x4d7/0x7b0 mm/slub.c:5408
kmemdup_noprof+0x2b/0x70 mm/util.c:138
kmemdup_noprof include/linux/fortify-string.h:763 [inline]
fib_rules_register+0x2f/0x400 net/core/fib_rules.c:170
fib4_rules_init+0x21/0x160 net/ipv4/fib_rules.c:508
ip_fib_net_init net/ipv4/fib_frontend.c:1578 [inline]
fib_net_init+0x17a/0x3e0 net/ipv4/fib_frontend.c:1628
ops_init+0x35d/0x5d0 net/core/net_namespace.c:137
setup_net+0x118/0x350 net/core/net_namespace.c:446
copy_net_ns+0x4f9/0x720 net/core/net_namespace.c:579
create_new_namespaces+0x3f0/0x6b0 kernel/nsproxy.c:132
unshare_nsproxy_namespaces+0x149/0x190 kernel/nsproxy.c:234
ksys_unshare+0x57d/0xa00 kernel/fork.c:3242
__do_sys_unshare kernel/fork.c:3316 [inline]
__se_sys_unshare kernel/fork.c:3314 [inline]
__x64_sys_unshare+0x38/0x50 kernel/fork.c:3314
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Freed by task 12641:
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:584
poison_slab_object mm/kasan/common.c:253 [inline]
__kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
kasan_slab_free include/linux/kasan.h:235 [inline]
slab_free_hook mm/slub.c:2689 [inline]
__rcu_free_sheaf_prepare+0x12d/0x2a0 mm/slub.c:2940
rcu_free_sheaf+0x31/0x200 mm/slub.c:5850
rcu_do_batch kernel/rcu/tree.c:2617 [inline]
rcu_core+0x78b/0x10a0 kernel/rcu/tree.c:2869
handle_softirqs+0x225/0x840 kernel/softirq.c:622
do_softirq+0x76/0xd0 kernel/softirq.c:523
__local_bh_enable_ip+0xf8/0x130 kernel/softirq.c:450
unregister_netdevice_many_notify+0x1874/0x2150 net/core/dev.c:12445
ops_exit_rtnl_list net/core/net_namespace.c:187 [inline]
ops_undo_list+0x391/0x8d0 net/core/net_namespace.c:248
cleanup_net+0x572/0x810 net/core/net_namespace.c:702
process_one_work kernel/workqueue.c:3314 [inline]
process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3397
worker_thread+0xa47/0xfb0 kernel/workqueue.c:3478
kthread+0x389/0x470 kernel/kthread.c:436
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
The buggy address belongs to the object at ffff88804ec4c600
which belongs to the cache kmalloc-192 of size 192
The buggy address is located 128 bytes inside of
freed 192-byte region [ffff88804ec4c600, ffff88804ec4c6c0)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x4ec4c
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000000 ffff88813fe163c0 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800100010 00000000f5000000 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 0xd2cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 13856, tgid 13853 (syz.3.2144), ts 351172300879, free_ts 351133053454
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x22d/0x280 mm/page_alloc.c:1853
prep_new_page mm/page_alloc.c:1861 [inline]
get_page_from_freelist+0x24ae/0x2530 mm/page_alloc.c:3941
__alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5221
alloc_slab_page mm/slub.c:3278 [inline]
allocate_slab+0x77/0x660 mm/slub.c:3467
new_slab mm/slub.c:3525 [inline]
refill_objects+0x336/0x3d0 mm/slub.c:7272
refill_sheaf mm/slub.c:2816 [inline]
__pcs_replace_empty_main+0x320/0x720 mm/slub.c:4652
alloc_from_pcs mm/slub.c:4750 [inline]
slab_alloc_node mm/slub.c:4884 [inline]
__do_kmalloc_node mm/slub.c:5295 [inline]
__kmalloc_noprof+0x464/0x750 mm/slub.c:5308
kmalloc_noprof include/linux/slab.h:954 [inline]
kzalloc_noprof include/linux/slab.h:1188 [inline]
new_dir fs/proc/proc_sysctl.c:966 [inline]
get_subdir fs/proc/proc_sysctl.c:1010 [inline]
sysctl_mkdir_p fs/proc/proc_sysctl.c:1320 [inline]
__register_sysctl_table+0xc02/0x1370 fs/proc/proc_sysctl.c:1395
neigh_sysctl_register+0x9b1/0xa90 net/core/neighbour.c:3915
addrconf_sysctl_register+0xb3/0x1c0 net/ipv6/addrconf.c:7396
ipv6_add_dev+0xd26/0x13a0 net/ipv6/addrconf.c:460
addrconf_notify+0x771/0x1050 net/ipv6/addrconf.c:3679
notifier_call_chain+0x1a5/0x3d0 kernel/notifier.c:85
call_netdevice_notifiers_extack net/core/dev.c:2288 [inline]
call_netdevice_notifiers net/core/dev.c:2302 [inline]
register_netdevice+0x18db/0x1f00 net/core/dev.c:11474
macsec_newlink+0x706/0x1200 drivers/net/macsec.c:4218
rtnl_newlink_create+0x310/0xb00 net/core/rtnetlink.c:3905
page last free pid 12657 tgid 12657 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
__free_pages_prepare mm/page_alloc.c:1397 [inline]
__free_frozen_pages+0xc0d/0xd20 mm/page_alloc.c:2938
__tlb_remove_table_free mm/mmu_gather.c:228 [inline]
tlb_remove_table_rcu+0x85/0x100 mm/mmu_gather.c:291
rcu_do_batch kernel/rcu/tree.c:2617 [inline]
rcu_core+0x78b/0x10a0 kernel/rcu/tree.c:2869
handle_softirqs+0x225/0x840 kernel/softirq.c:622
__do_softirq kernel/softirq.c:656 [inline]
invoke_softirq kernel/softirq.c:496 [inline]
__irq_exit_rcu+0xca/0x220 kernel/softirq.c:735
irq_exit_rcu+0x9/0x30 kernel/softirq.c:752
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1061 [inline]
sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1061
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
Memory state around the buggy address:
ffff88804ec4c580: 00 00 00 fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88804ec4c600: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88804ec4c680: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
^
ffff88804ec4c700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff88804ec4c780: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
==================================================================
---
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [syzbot] [net?] KASAN: slab-use-after-free Read in fib_rules_lookup
2026-06-16 14:05 [syzbot] [net?] KASAN: slab-use-after-free Read in fib_rules_lookup syzbot
@ 2026-06-16 15:31 ` Ido Schimmel
2026-06-16 15:55 ` Eric Dumazet
0 siblings, 1 reply; 5+ messages in thread
From: Ido Schimmel @ 2026-06-16 15:31 UTC (permalink / raw)
To: syzbot, kuniyu
Cc: davem, dsahern, edumazet, horms, kuba, linux-kernel, netdev,
pabeni, syzkaller-bugs
On Tue, Jun 16, 2026 at 07:05:24AM -0700, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 72dfa4700f78 net: dsa: sja1105: fix lastused timestamp in ..
This includes commit 759923cf03b0 ("ipv4: fib: Convert
fib_net_exit_batch() to ->exit_rtnl().") that moved ip_fib_net_exit()
(and therefore fib4_rules_exit()) earlier in the netns dismantle path.
Kuniyuki, can you please take a look?
You can use this to reproduce:
#!/bin/bash
while true; do
ip netns add ns1
ip -n ns1 link set dev lo up
ip -n ns1 address add 192.0.2.1/24 dev lo
ip -n ns1 link add name dummy1 up type dummy
ip -n ns1 address add 198.51.100.1/24 dev dummy1
ip -n ns1 rule add ipproto tcp sport 12345 table 12345
ip -n ns1 fou add port 5555 ipproto 47 local 192.0.2.1 peer 198.51.100.2 peer_port 54321
ip netns del ns1
done
Thanks
> git tree: net-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=15794bd2580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=a0842261b62cdea8
> dashboard link: https://syzkaller.appspot.com/bug?extid=965506b59a2de0b6905c
> compiler: Debian clang version 22.1.6 (++20260514074242+fc4aad7b5db3-1~exp1~20260514074407.73), Debian LLD 22.1.6
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/d4e16f50a97c/disk-72dfa470.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/6cd4a736e796/vmlinux-72dfa470.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/548b0011c8e8/bzImage-72dfa470.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+965506b59a2de0b6905c@syzkaller.appspotmail.com
>
> bond0 (unregistering): Released all slaves
> bond1 (unregistering): Released all slaves
> bond2 (unregistering): (slave dummy0): Releasing active interface
> bond2 (unregistering): Released all slaves
> ==================================================================
> BUG: KASAN: slab-use-after-free in fib_rules_lookup+0x15e/0xeb0 net/core/fib_rules.c:321
> Read of size 8 at addr ffff88804ec4c680 by task kworker/u8:21/12641
>
> CPU: 0 UID: 0 PID: 12641 Comm: kworker/u8:21 Not tainted syzkaller #0 PREEMPT(full)
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
> Workqueue: netns cleanup_net
> Call Trace:
> <TASK>
> dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
> print_address_description+0x55/0x1e0 mm/kasan/report.c:378
> print_report+0x58/0x70 mm/kasan/report.c:482
> kasan_report+0x117/0x150 mm/kasan/report.c:595
> fib_rules_lookup+0x15e/0xeb0 net/core/fib_rules.c:321
> __fib_lookup+0x106/0x210 net/ipv4/fib_rules.c:96
> ip_route_output_key_hash_rcu+0x294/0x2720 net/ipv4/route.c:2811
> ip_route_output_key_hash+0x18d/0x2a0 net/ipv4/route.c:2702
> __ip_route_output_key include/net/route.h:169 [inline]
> ip_route_output_flow+0x2a/0x150 net/ipv4/route.c:2929
> ip4_datagram_release_cb+0x89d/0xbe0 net/ipv4/datagram.c:118
> release_sock+0x206/0x260 net/core/sock.c:3861
> inet_shutdown+0x2b1/0x390 net/ipv4/af_inet.c:950
> udp_tunnel_sock_release+0x6d/0x80 net/ipv4/udp_tunnel_core.c:197
> fou_release net/ipv4/fou_core.c:562 [inline]
> fou_exit_net+0x17d/0x1f0 net/ipv4/fou_core.c:1230
> ops_exit_list net/core/net_namespace.c:199 [inline]
> ops_undo_list+0x43d/0x8d0 net/core/net_namespace.c:252
> cleanup_net+0x572/0x810 net/core/net_namespace.c:702
> process_one_work kernel/workqueue.c:3314 [inline]
> process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3397
> worker_thread+0xa47/0xfb0 kernel/workqueue.c:3478
> kthread+0x389/0x470 kernel/kthread.c:436
> ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
> ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
> </TASK>
>
> Allocated by task 19121:
> kasan_save_stack mm/kasan/common.c:57 [inline]
> kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
> poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
> __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415
> kasan_kmalloc include/linux/kasan.h:263 [inline]
> __do_kmalloc_node mm/slub.c:5296 [inline]
> __kmalloc_node_track_caller_noprof+0x4d7/0x7b0 mm/slub.c:5408
> kmemdup_noprof+0x2b/0x70 mm/util.c:138
> kmemdup_noprof include/linux/fortify-string.h:763 [inline]
> fib_rules_register+0x2f/0x400 net/core/fib_rules.c:170
> fib4_rules_init+0x21/0x160 net/ipv4/fib_rules.c:508
> ip_fib_net_init net/ipv4/fib_frontend.c:1578 [inline]
> fib_net_init+0x17a/0x3e0 net/ipv4/fib_frontend.c:1628
> ops_init+0x35d/0x5d0 net/core/net_namespace.c:137
> setup_net+0x118/0x350 net/core/net_namespace.c:446
> copy_net_ns+0x4f9/0x720 net/core/net_namespace.c:579
> create_new_namespaces+0x3f0/0x6b0 kernel/nsproxy.c:132
> unshare_nsproxy_namespaces+0x149/0x190 kernel/nsproxy.c:234
> ksys_unshare+0x57d/0xa00 kernel/fork.c:3242
> __do_sys_unshare kernel/fork.c:3316 [inline]
> __se_sys_unshare kernel/fork.c:3314 [inline]
> __x64_sys_unshare+0x38/0x50 kernel/fork.c:3314
> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> Freed by task 12641:
> kasan_save_stack mm/kasan/common.c:57 [inline]
> kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
> kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:584
> poison_slab_object mm/kasan/common.c:253 [inline]
> __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
> kasan_slab_free include/linux/kasan.h:235 [inline]
> slab_free_hook mm/slub.c:2689 [inline]
> __rcu_free_sheaf_prepare+0x12d/0x2a0 mm/slub.c:2940
> rcu_free_sheaf+0x31/0x200 mm/slub.c:5850
> rcu_do_batch kernel/rcu/tree.c:2617 [inline]
> rcu_core+0x78b/0x10a0 kernel/rcu/tree.c:2869
> handle_softirqs+0x225/0x840 kernel/softirq.c:622
> do_softirq+0x76/0xd0 kernel/softirq.c:523
> __local_bh_enable_ip+0xf8/0x130 kernel/softirq.c:450
> unregister_netdevice_many_notify+0x1874/0x2150 net/core/dev.c:12445
> ops_exit_rtnl_list net/core/net_namespace.c:187 [inline]
> ops_undo_list+0x391/0x8d0 net/core/net_namespace.c:248
> cleanup_net+0x572/0x810 net/core/net_namespace.c:702
> process_one_work kernel/workqueue.c:3314 [inline]
> process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3397
> worker_thread+0xa47/0xfb0 kernel/workqueue.c:3478
> kthread+0x389/0x470 kernel/kthread.c:436
> ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
> ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
>
> The buggy address belongs to the object at ffff88804ec4c600
> which belongs to the cache kmalloc-192 of size 192
> The buggy address is located 128 bytes inside of
> freed 192-byte region [ffff88804ec4c600, ffff88804ec4c6c0)
>
> The buggy address belongs to the physical page:
> page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x4ec4c
> flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
> page_type: f5(slab)
> raw: 00fff00000000000 ffff88813fe163c0 dead000000000100 dead000000000122
> raw: 0000000000000000 0000000800100010 00000000f5000000 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 0xd2cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 13856, tgid 13853 (syz.3.2144), ts 351172300879, free_ts 351133053454
> set_page_owner include/linux/page_owner.h:32 [inline]
> post_alloc_hook+0x22d/0x280 mm/page_alloc.c:1853
> prep_new_page mm/page_alloc.c:1861 [inline]
> get_page_from_freelist+0x24ae/0x2530 mm/page_alloc.c:3941
> __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5221
> alloc_slab_page mm/slub.c:3278 [inline]
> allocate_slab+0x77/0x660 mm/slub.c:3467
> new_slab mm/slub.c:3525 [inline]
> refill_objects+0x336/0x3d0 mm/slub.c:7272
> refill_sheaf mm/slub.c:2816 [inline]
> __pcs_replace_empty_main+0x320/0x720 mm/slub.c:4652
> alloc_from_pcs mm/slub.c:4750 [inline]
> slab_alloc_node mm/slub.c:4884 [inline]
> __do_kmalloc_node mm/slub.c:5295 [inline]
> __kmalloc_noprof+0x464/0x750 mm/slub.c:5308
> kmalloc_noprof include/linux/slab.h:954 [inline]
> kzalloc_noprof include/linux/slab.h:1188 [inline]
> new_dir fs/proc/proc_sysctl.c:966 [inline]
> get_subdir fs/proc/proc_sysctl.c:1010 [inline]
> sysctl_mkdir_p fs/proc/proc_sysctl.c:1320 [inline]
> __register_sysctl_table+0xc02/0x1370 fs/proc/proc_sysctl.c:1395
> neigh_sysctl_register+0x9b1/0xa90 net/core/neighbour.c:3915
> addrconf_sysctl_register+0xb3/0x1c0 net/ipv6/addrconf.c:7396
> ipv6_add_dev+0xd26/0x13a0 net/ipv6/addrconf.c:460
> addrconf_notify+0x771/0x1050 net/ipv6/addrconf.c:3679
> notifier_call_chain+0x1a5/0x3d0 kernel/notifier.c:85
> call_netdevice_notifiers_extack net/core/dev.c:2288 [inline]
> call_netdevice_notifiers net/core/dev.c:2302 [inline]
> register_netdevice+0x18db/0x1f00 net/core/dev.c:11474
> macsec_newlink+0x706/0x1200 drivers/net/macsec.c:4218
> rtnl_newlink_create+0x310/0xb00 net/core/rtnetlink.c:3905
> page last free pid 12657 tgid 12657 stack trace:
> reset_page_owner include/linux/page_owner.h:25 [inline]
> __free_pages_prepare mm/page_alloc.c:1397 [inline]
> __free_frozen_pages+0xc0d/0xd20 mm/page_alloc.c:2938
> __tlb_remove_table_free mm/mmu_gather.c:228 [inline]
> tlb_remove_table_rcu+0x85/0x100 mm/mmu_gather.c:291
> rcu_do_batch kernel/rcu/tree.c:2617 [inline]
> rcu_core+0x78b/0x10a0 kernel/rcu/tree.c:2869
> handle_softirqs+0x225/0x840 kernel/softirq.c:622
> __do_softirq kernel/softirq.c:656 [inline]
> invoke_softirq kernel/softirq.c:496 [inline]
> __irq_exit_rcu+0xca/0x220 kernel/softirq.c:735
> irq_exit_rcu+0x9/0x30 kernel/softirq.c:752
> instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1061 [inline]
> sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1061
> asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
>
> Memory state around the buggy address:
> ffff88804ec4c580: 00 00 00 fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff88804ec4c600: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >ffff88804ec4c680: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
> ^
> ffff88804ec4c700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> ffff88804ec4c780: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
> ==================================================================
>
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@googlegroups.com.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>
> If the report is already addressed, let syzbot know by replying with:
> #syz fix: exact-commit-title
>
> If you want to overwrite report's subsystems, reply with:
> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
>
> If the report is a duplicate of another one, reply with:
> #syz dup: exact-subject-of-another-report
>
> If you want to undo deduplication, reply with:
> #syz undup
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [syzbot] [net?] KASAN: slab-use-after-free Read in fib_rules_lookup
2026-06-16 15:31 ` Ido Schimmel
@ 2026-06-16 15:55 ` Eric Dumazet
2026-06-16 17:06 ` Kuniyuki Iwashima
0 siblings, 1 reply; 5+ messages in thread
From: Eric Dumazet @ 2026-06-16 15:55 UTC (permalink / raw)
To: Ido Schimmel
Cc: syzbot, kuniyu, davem, dsahern, horms, kuba, linux-kernel, netdev,
pabeni, syzkaller-bugs
On Tue, Jun 16, 2026 at 8:31 AM Ido Schimmel <idosch@nvidia.com> wrote:
>
> On Tue, Jun 16, 2026 at 07:05:24AM -0700, syzbot wrote:
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit: 72dfa4700f78 net: dsa: sja1105: fix lastused timestamp in ..
>
> This includes commit 759923cf03b0 ("ipv4: fib: Convert
> fib_net_exit_batch() to ->exit_rtnl().") that moved ip_fib_net_exit()
> (and therefore fib4_rules_exit()) earlier in the netns dismantle path.
>
> Kuniyuki, can you please take a look?
>
> You can use this to reproduce:
>
> #!/bin/bash
>
> while true; do
> ip netns add ns1
> ip -n ns1 link set dev lo up
> ip -n ns1 address add 192.0.2.1/24 dev lo
> ip -n ns1 link add name dummy1 up type dummy
> ip -n ns1 address add 198.51.100.1/24 dev dummy1
> ip -n ns1 rule add ipproto tcp sport 12345 table 12345
> ip -n ns1 fou add port 5555 ipproto 47 local 192.0.2.1 peer 198.51.100.2 peer_port 54321
> ip netns del ns1
> done
>
Oh right.
While looking at this syzbot report I also found an old issue.
https://lore.kernel.org/netdev/20260616141317.407791-1-edumazet@google.com/T/#u
I guess adding some delays in enqueue_to_backlog() could trigger a
similar bug even if we revert Kuniyuki's patch.
> Thanks
>
> > git tree: net-next
> > console output: https://syzkaller.appspot.com/x/log.txt?x=15794bd2580000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=a0842261b62cdea8
> > dashboard link: https://syzkaller.appspot.com/bug?extid=965506b59a2de0b6905c
> > compiler: Debian clang version 22.1.6 (++20260514074242+fc4aad7b5db3-1~exp1~20260514074407.73), Debian LLD 22.1.6
> >
> > Unfortunately, I don't have any reproducer for this issue yet.
> >
> > Downloadable assets:
> > disk image: https://storage.googleapis.com/syzbot-assets/d4e16f50a97c/disk-72dfa470.raw.xz
> > vmlinux: https://storage.googleapis.com/syzbot-assets/6cd4a736e796/vmlinux-72dfa470.xz
> > kernel image: https://storage.googleapis.com/syzbot-assets/548b0011c8e8/bzImage-72dfa470.xz
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+965506b59a2de0b6905c@syzkaller.appspotmail.com
> >
> > bond0 (unregistering): Released all slaves
> > bond1 (unregistering): Released all slaves
> > bond2 (unregistering): (slave dummy0): Releasing active interface
> > bond2 (unregistering): Released all slaves
> > ==================================================================
> > BUG: KASAN: slab-use-after-free in fib_rules_lookup+0x15e/0xeb0 net/core/fib_rules.c:321
> > Read of size 8 at addr ffff88804ec4c680 by task kworker/u8:21/12641
> >
> > CPU: 0 UID: 0 PID: 12641 Comm: kworker/u8:21 Not tainted syzkaller #0 PREEMPT(full)
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
> > Workqueue: netns cleanup_net
> > Call Trace:
> > <TASK>
> > dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
> > print_address_description+0x55/0x1e0 mm/kasan/report.c:378
> > print_report+0x58/0x70 mm/kasan/report.c:482
> > kasan_report+0x117/0x150 mm/kasan/report.c:595
> > fib_rules_lookup+0x15e/0xeb0 net/core/fib_rules.c:321
> > __fib_lookup+0x106/0x210 net/ipv4/fib_rules.c:96
> > ip_route_output_key_hash_rcu+0x294/0x2720 net/ipv4/route.c:2811
> > ip_route_output_key_hash+0x18d/0x2a0 net/ipv4/route.c:2702
> > __ip_route_output_key include/net/route.h:169 [inline]
> > ip_route_output_flow+0x2a/0x150 net/ipv4/route.c:2929
> > ip4_datagram_release_cb+0x89d/0xbe0 net/ipv4/datagram.c:118
> > release_sock+0x206/0x260 net/core/sock.c:3861
> > inet_shutdown+0x2b1/0x390 net/ipv4/af_inet.c:950
> > udp_tunnel_sock_release+0x6d/0x80 net/ipv4/udp_tunnel_core.c:197
> > fou_release net/ipv4/fou_core.c:562 [inline]
> > fou_exit_net+0x17d/0x1f0 net/ipv4/fou_core.c:1230
> > ops_exit_list net/core/net_namespace.c:199 [inline]
> > ops_undo_list+0x43d/0x8d0 net/core/net_namespace.c:252
> > cleanup_net+0x572/0x810 net/core/net_namespace.c:702
> > process_one_work kernel/workqueue.c:3314 [inline]
> > process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3397
> > worker_thread+0xa47/0xfb0 kernel/workqueue.c:3478
> > kthread+0x389/0x470 kernel/kthread.c:436
> > ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
> > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
> > </TASK>
> >
> > Allocated by task 19121:
> > kasan_save_stack mm/kasan/common.c:57 [inline]
> > kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
> > poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
> > __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415
> > kasan_kmalloc include/linux/kasan.h:263 [inline]
> > __do_kmalloc_node mm/slub.c:5296 [inline]
> > __kmalloc_node_track_caller_noprof+0x4d7/0x7b0 mm/slub.c:5408
> > kmemdup_noprof+0x2b/0x70 mm/util.c:138
> > kmemdup_noprof include/linux/fortify-string.h:763 [inline]
> > fib_rules_register+0x2f/0x400 net/core/fib_rules.c:170
> > fib4_rules_init+0x21/0x160 net/ipv4/fib_rules.c:508
> > ip_fib_net_init net/ipv4/fib_frontend.c:1578 [inline]
> > fib_net_init+0x17a/0x3e0 net/ipv4/fib_frontend.c:1628
> > ops_init+0x35d/0x5d0 net/core/net_namespace.c:137
> > setup_net+0x118/0x350 net/core/net_namespace.c:446
> > copy_net_ns+0x4f9/0x720 net/core/net_namespace.c:579
> > create_new_namespaces+0x3f0/0x6b0 kernel/nsproxy.c:132
> > unshare_nsproxy_namespaces+0x149/0x190 kernel/nsproxy.c:234
> > ksys_unshare+0x57d/0xa00 kernel/fork.c:3242
> > __do_sys_unshare kernel/fork.c:3316 [inline]
> > __se_sys_unshare kernel/fork.c:3314 [inline]
> > __x64_sys_unshare+0x38/0x50 kernel/fork.c:3314
> > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> > do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
> > entry_SYSCALL_64_after_hwframe+0x77/0x7f
> >
> > Freed by task 12641:
> > kasan_save_stack mm/kasan/common.c:57 [inline]
> > kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
> > kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:584
> > poison_slab_object mm/kasan/common.c:253 [inline]
> > __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
> > kasan_slab_free include/linux/kasan.h:235 [inline]
> > slab_free_hook mm/slub.c:2689 [inline]
> > __rcu_free_sheaf_prepare+0x12d/0x2a0 mm/slub.c:2940
> > rcu_free_sheaf+0x31/0x200 mm/slub.c:5850
> > rcu_do_batch kernel/rcu/tree.c:2617 [inline]
> > rcu_core+0x78b/0x10a0 kernel/rcu/tree.c:2869
> > handle_softirqs+0x225/0x840 kernel/softirq.c:622
> > do_softirq+0x76/0xd0 kernel/softirq.c:523
> > __local_bh_enable_ip+0xf8/0x130 kernel/softirq.c:450
> > unregister_netdevice_many_notify+0x1874/0x2150 net/core/dev.c:12445
> > ops_exit_rtnl_list net/core/net_namespace.c:187 [inline]
> > ops_undo_list+0x391/0x8d0 net/core/net_namespace.c:248
> > cleanup_net+0x572/0x810 net/core/net_namespace.c:702
> > process_one_work kernel/workqueue.c:3314 [inline]
> > process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3397
> > worker_thread+0xa47/0xfb0 kernel/workqueue.c:3478
> > kthread+0x389/0x470 kernel/kthread.c:436
> > ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
> > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
> >
> > The buggy address belongs to the object at ffff88804ec4c600
> > which belongs to the cache kmalloc-192 of size 192
> > The buggy address is located 128 bytes inside of
> > freed 192-byte region [ffff88804ec4c600, ffff88804ec4c6c0)
> >
> > The buggy address belongs to the physical page:
> > page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x4ec4c
> > flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
> > page_type: f5(slab)
> > raw: 00fff00000000000 ffff88813fe163c0 dead000000000100 dead000000000122
> > raw: 0000000000000000 0000000800100010 00000000f5000000 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 0xd2cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 13856, tgid 13853 (syz.3.2144), ts 351172300879, free_ts 351133053454
> > set_page_owner include/linux/page_owner.h:32 [inline]
> > post_alloc_hook+0x22d/0x280 mm/page_alloc.c:1853
> > prep_new_page mm/page_alloc.c:1861 [inline]
> > get_page_from_freelist+0x24ae/0x2530 mm/page_alloc.c:3941
> > __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5221
> > alloc_slab_page mm/slub.c:3278 [inline]
> > allocate_slab+0x77/0x660 mm/slub.c:3467
> > new_slab mm/slub.c:3525 [inline]
> > refill_objects+0x336/0x3d0 mm/slub.c:7272
> > refill_sheaf mm/slub.c:2816 [inline]
> > __pcs_replace_empty_main+0x320/0x720 mm/slub.c:4652
> > alloc_from_pcs mm/slub.c:4750 [inline]
> > slab_alloc_node mm/slub.c:4884 [inline]
> > __do_kmalloc_node mm/slub.c:5295 [inline]
> > __kmalloc_noprof+0x464/0x750 mm/slub.c:5308
> > kmalloc_noprof include/linux/slab.h:954 [inline]
> > kzalloc_noprof include/linux/slab.h:1188 [inline]
> > new_dir fs/proc/proc_sysctl.c:966 [inline]
> > get_subdir fs/proc/proc_sysctl.c:1010 [inline]
> > sysctl_mkdir_p fs/proc/proc_sysctl.c:1320 [inline]
> > __register_sysctl_table+0xc02/0x1370 fs/proc/proc_sysctl.c:1395
> > neigh_sysctl_register+0x9b1/0xa90 net/core/neighbour.c:3915
> > addrconf_sysctl_register+0xb3/0x1c0 net/ipv6/addrconf.c:7396
> > ipv6_add_dev+0xd26/0x13a0 net/ipv6/addrconf.c:460
> > addrconf_notify+0x771/0x1050 net/ipv6/addrconf.c:3679
> > notifier_call_chain+0x1a5/0x3d0 kernel/notifier.c:85
> > call_netdevice_notifiers_extack net/core/dev.c:2288 [inline]
> > call_netdevice_notifiers net/core/dev.c:2302 [inline]
> > register_netdevice+0x18db/0x1f00 net/core/dev.c:11474
> > macsec_newlink+0x706/0x1200 drivers/net/macsec.c:4218
> > rtnl_newlink_create+0x310/0xb00 net/core/rtnetlink.c:3905
> > page last free pid 12657 tgid 12657 stack trace:
> > reset_page_owner include/linux/page_owner.h:25 [inline]
> > __free_pages_prepare mm/page_alloc.c:1397 [inline]
> > __free_frozen_pages+0xc0d/0xd20 mm/page_alloc.c:2938
> > __tlb_remove_table_free mm/mmu_gather.c:228 [inline]
> > tlb_remove_table_rcu+0x85/0x100 mm/mmu_gather.c:291
> > rcu_do_batch kernel/rcu/tree.c:2617 [inline]
> > rcu_core+0x78b/0x10a0 kernel/rcu/tree.c:2869
> > handle_softirqs+0x225/0x840 kernel/softirq.c:622
> > __do_softirq kernel/softirq.c:656 [inline]
> > invoke_softirq kernel/softirq.c:496 [inline]
> > __irq_exit_rcu+0xca/0x220 kernel/softirq.c:735
> > irq_exit_rcu+0x9/0x30 kernel/softirq.c:752
> > instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1061 [inline]
> > sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1061
> > asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
> >
> > Memory state around the buggy address:
> > ffff88804ec4c580: 00 00 00 fc fc fc fc fc fc fc fc fc fc fc fc fc
> > ffff88804ec4c600: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > >ffff88804ec4c680: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
> > ^
> > ffff88804ec4c700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> > ffff88804ec4c780: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
> > ==================================================================
> >
> >
> > ---
> > This report is generated by a bot. It may contain errors.
> > See https://goo.gl/tpsmEJ for more information about syzbot.
> > syzbot engineers can be reached at syzkaller@googlegroups.com.
> >
> > syzbot will keep track of this issue. See:
> > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> >
> > If the report is already addressed, let syzbot know by replying with:
> > #syz fix: exact-commit-title
> >
> > If you want to overwrite report's subsystems, reply with:
> > #syz set subsystems: new-subsystem
> > (See the list of subsystem names on the web dashboard)
> >
> > If the report is a duplicate of another one, reply with:
> > #syz dup: exact-subject-of-another-report
> >
> > If you want to undo deduplication, reply with:
> > #syz undup
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [syzbot] [net?] KASAN: slab-use-after-free Read in fib_rules_lookup
2026-06-16 15:55 ` Eric Dumazet
@ 2026-06-16 17:06 ` Kuniyuki Iwashima
2026-06-16 17:59 ` Kuniyuki Iwashima
0 siblings, 1 reply; 5+ messages in thread
From: Kuniyuki Iwashima @ 2026-06-16 17:06 UTC (permalink / raw)
To: Eric Dumazet
Cc: Ido Schimmel, syzbot, davem, dsahern, horms, kuba, linux-kernel,
netdev, pabeni, syzkaller-bugs
On Tue, Jun 16, 2026 at 8:55 AM Eric Dumazet <edumazet@google.com> wrote:
>
> On Tue, Jun 16, 2026 at 8:31 AM Ido Schimmel <idosch@nvidia.com> wrote:
> >
> > On Tue, Jun 16, 2026 at 07:05:24AM -0700, syzbot wrote:
> > > Hello,
> > >
> > > syzbot found the following issue on:
> > >
> > > HEAD commit: 72dfa4700f78 net: dsa: sja1105: fix lastused timestamp in ..
> >
> > This includes commit 759923cf03b0 ("ipv4: fib: Convert
> > fib_net_exit_batch() to ->exit_rtnl().") that moved ip_fib_net_exit()
> > (and therefore fib4_rules_exit()) earlier in the netns dismantle path.
> >
> > Kuniyuki, can you please take a look?
> >
> > You can use this to reproduce:
> >
> > #!/bin/bash
> >
> > while true; do
> > ip netns add ns1
> > ip -n ns1 link set dev lo up
> > ip -n ns1 address add 192.0.2.1/24 dev lo
> > ip -n ns1 link add name dummy1 up type dummy
> > ip -n ns1 address add 198.51.100.1/24 dev dummy1
> > ip -n ns1 rule add ipproto tcp sport 12345 table 12345
> > ip -n ns1 fou add port 5555 ipproto 47 local 192.0.2.1 peer 198.51.100.2 peer_port 54321
> > ip netns del ns1
> > done
> >
>
> Oh right.
>
> While looking at this syzbot report I also found an old issue.
>
> https://lore.kernel.org/netdev/20260616141317.407791-1-edumazet@google.com/T/#u
>
> I guess adding some delays in enqueue_to_backlog() could trigger a
> similar bug even if we revert Kuniyuki's patch.
I'll look into it, thank you both !
>
>
>
>
> > Thanks
> >
> > > git tree: net-next
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=15794bd2580000
> > > kernel config: https://syzkaller.appspot.com/x/.config?x=a0842261b62cdea8
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=965506b59a2de0b6905c
> > > compiler: Debian clang version 22.1.6 (++20260514074242+fc4aad7b5db3-1~exp1~20260514074407.73), Debian LLD 22.1.6
> > >
> > > Unfortunately, I don't have any reproducer for this issue yet.
> > >
> > > Downloadable assets:
> > > disk image: https://storage.googleapis.com/syzbot-assets/d4e16f50a97c/disk-72dfa470.raw.xz
> > > vmlinux: https://storage.googleapis.com/syzbot-assets/6cd4a736e796/vmlinux-72dfa470.xz
> > > kernel image: https://storage.googleapis.com/syzbot-assets/548b0011c8e8/bzImage-72dfa470.xz
> > >
> > > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > > Reported-by: syzbot+965506b59a2de0b6905c@syzkaller.appspotmail.com
> > >
> > > bond0 (unregistering): Released all slaves
> > > bond1 (unregistering): Released all slaves
> > > bond2 (unregistering): (slave dummy0): Releasing active interface
> > > bond2 (unregistering): Released all slaves
> > > ==================================================================
> > > BUG: KASAN: slab-use-after-free in fib_rules_lookup+0x15e/0xeb0 net/core/fib_rules.c:321
> > > Read of size 8 at addr ffff88804ec4c680 by task kworker/u8:21/12641
> > >
> > > CPU: 0 UID: 0 PID: 12641 Comm: kworker/u8:21 Not tainted syzkaller #0 PREEMPT(full)
> > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
> > > Workqueue: netns cleanup_net
> > > Call Trace:
> > > <TASK>
> > > dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
> > > print_address_description+0x55/0x1e0 mm/kasan/report.c:378
> > > print_report+0x58/0x70 mm/kasan/report.c:482
> > > kasan_report+0x117/0x150 mm/kasan/report.c:595
> > > fib_rules_lookup+0x15e/0xeb0 net/core/fib_rules.c:321
> > > __fib_lookup+0x106/0x210 net/ipv4/fib_rules.c:96
> > > ip_route_output_key_hash_rcu+0x294/0x2720 net/ipv4/route.c:2811
> > > ip_route_output_key_hash+0x18d/0x2a0 net/ipv4/route.c:2702
> > > __ip_route_output_key include/net/route.h:169 [inline]
> > > ip_route_output_flow+0x2a/0x150 net/ipv4/route.c:2929
> > > ip4_datagram_release_cb+0x89d/0xbe0 net/ipv4/datagram.c:118
> > > release_sock+0x206/0x260 net/core/sock.c:3861
> > > inet_shutdown+0x2b1/0x390 net/ipv4/af_inet.c:950
> > > udp_tunnel_sock_release+0x6d/0x80 net/ipv4/udp_tunnel_core.c:197
> > > fou_release net/ipv4/fou_core.c:562 [inline]
> > > fou_exit_net+0x17d/0x1f0 net/ipv4/fou_core.c:1230
> > > ops_exit_list net/core/net_namespace.c:199 [inline]
> > > ops_undo_list+0x43d/0x8d0 net/core/net_namespace.c:252
> > > cleanup_net+0x572/0x810 net/core/net_namespace.c:702
> > > process_one_work kernel/workqueue.c:3314 [inline]
> > > process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3397
> > > worker_thread+0xa47/0xfb0 kernel/workqueue.c:3478
> > > kthread+0x389/0x470 kernel/kthread.c:436
> > > ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
> > > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
> > > </TASK>
> > >
> > > Allocated by task 19121:
> > > kasan_save_stack mm/kasan/common.c:57 [inline]
> > > kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
> > > poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
> > > __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415
> > > kasan_kmalloc include/linux/kasan.h:263 [inline]
> > > __do_kmalloc_node mm/slub.c:5296 [inline]
> > > __kmalloc_node_track_caller_noprof+0x4d7/0x7b0 mm/slub.c:5408
> > > kmemdup_noprof+0x2b/0x70 mm/util.c:138
> > > kmemdup_noprof include/linux/fortify-string.h:763 [inline]
> > > fib_rules_register+0x2f/0x400 net/core/fib_rules.c:170
> > > fib4_rules_init+0x21/0x160 net/ipv4/fib_rules.c:508
> > > ip_fib_net_init net/ipv4/fib_frontend.c:1578 [inline]
> > > fib_net_init+0x17a/0x3e0 net/ipv4/fib_frontend.c:1628
> > > ops_init+0x35d/0x5d0 net/core/net_namespace.c:137
> > > setup_net+0x118/0x350 net/core/net_namespace.c:446
> > > copy_net_ns+0x4f9/0x720 net/core/net_namespace.c:579
> > > create_new_namespaces+0x3f0/0x6b0 kernel/nsproxy.c:132
> > > unshare_nsproxy_namespaces+0x149/0x190 kernel/nsproxy.c:234
> > > ksys_unshare+0x57d/0xa00 kernel/fork.c:3242
> > > __do_sys_unshare kernel/fork.c:3316 [inline]
> > > __se_sys_unshare kernel/fork.c:3314 [inline]
> > > __x64_sys_unshare+0x38/0x50 kernel/fork.c:3314
> > > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> > > do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
> > > entry_SYSCALL_64_after_hwframe+0x77/0x7f
> > >
> > > Freed by task 12641:
> > > kasan_save_stack mm/kasan/common.c:57 [inline]
> > > kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
> > > kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:584
> > > poison_slab_object mm/kasan/common.c:253 [inline]
> > > __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
> > > kasan_slab_free include/linux/kasan.h:235 [inline]
> > > slab_free_hook mm/slub.c:2689 [inline]
> > > __rcu_free_sheaf_prepare+0x12d/0x2a0 mm/slub.c:2940
> > > rcu_free_sheaf+0x31/0x200 mm/slub.c:5850
> > > rcu_do_batch kernel/rcu/tree.c:2617 [inline]
> > > rcu_core+0x78b/0x10a0 kernel/rcu/tree.c:2869
> > > handle_softirqs+0x225/0x840 kernel/softirq.c:622
> > > do_softirq+0x76/0xd0 kernel/softirq.c:523
> > > __local_bh_enable_ip+0xf8/0x130 kernel/softirq.c:450
> > > unregister_netdevice_many_notify+0x1874/0x2150 net/core/dev.c:12445
> > > ops_exit_rtnl_list net/core/net_namespace.c:187 [inline]
> > > ops_undo_list+0x391/0x8d0 net/core/net_namespace.c:248
> > > cleanup_net+0x572/0x810 net/core/net_namespace.c:702
> > > process_one_work kernel/workqueue.c:3314 [inline]
> > > process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3397
> > > worker_thread+0xa47/0xfb0 kernel/workqueue.c:3478
> > > kthread+0x389/0x470 kernel/kthread.c:436
> > > ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
> > > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
> > >
> > > The buggy address belongs to the object at ffff88804ec4c600
> > > which belongs to the cache kmalloc-192 of size 192
> > > The buggy address is located 128 bytes inside of
> > > freed 192-byte region [ffff88804ec4c600, ffff88804ec4c6c0)
> > >
> > > The buggy address belongs to the physical page:
> > > page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x4ec4c
> > > flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
> > > page_type: f5(slab)
> > > raw: 00fff00000000000 ffff88813fe163c0 dead000000000100 dead000000000122
> > > raw: 0000000000000000 0000000800100010 00000000f5000000 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 0xd2cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 13856, tgid 13853 (syz.3.2144), ts 351172300879, free_ts 351133053454
> > > set_page_owner include/linux/page_owner.h:32 [inline]
> > > post_alloc_hook+0x22d/0x280 mm/page_alloc.c:1853
> > > prep_new_page mm/page_alloc.c:1861 [inline]
> > > get_page_from_freelist+0x24ae/0x2530 mm/page_alloc.c:3941
> > > __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5221
> > > alloc_slab_page mm/slub.c:3278 [inline]
> > > allocate_slab+0x77/0x660 mm/slub.c:3467
> > > new_slab mm/slub.c:3525 [inline]
> > > refill_objects+0x336/0x3d0 mm/slub.c:7272
> > > refill_sheaf mm/slub.c:2816 [inline]
> > > __pcs_replace_empty_main+0x320/0x720 mm/slub.c:4652
> > > alloc_from_pcs mm/slub.c:4750 [inline]
> > > slab_alloc_node mm/slub.c:4884 [inline]
> > > __do_kmalloc_node mm/slub.c:5295 [inline]
> > > __kmalloc_noprof+0x464/0x750 mm/slub.c:5308
> > > kmalloc_noprof include/linux/slab.h:954 [inline]
> > > kzalloc_noprof include/linux/slab.h:1188 [inline]
> > > new_dir fs/proc/proc_sysctl.c:966 [inline]
> > > get_subdir fs/proc/proc_sysctl.c:1010 [inline]
> > > sysctl_mkdir_p fs/proc/proc_sysctl.c:1320 [inline]
> > > __register_sysctl_table+0xc02/0x1370 fs/proc/proc_sysctl.c:1395
> > > neigh_sysctl_register+0x9b1/0xa90 net/core/neighbour.c:3915
> > > addrconf_sysctl_register+0xb3/0x1c0 net/ipv6/addrconf.c:7396
> > > ipv6_add_dev+0xd26/0x13a0 net/ipv6/addrconf.c:460
> > > addrconf_notify+0x771/0x1050 net/ipv6/addrconf.c:3679
> > > notifier_call_chain+0x1a5/0x3d0 kernel/notifier.c:85
> > > call_netdevice_notifiers_extack net/core/dev.c:2288 [inline]
> > > call_netdevice_notifiers net/core/dev.c:2302 [inline]
> > > register_netdevice+0x18db/0x1f00 net/core/dev.c:11474
> > > macsec_newlink+0x706/0x1200 drivers/net/macsec.c:4218
> > > rtnl_newlink_create+0x310/0xb00 net/core/rtnetlink.c:3905
> > > page last free pid 12657 tgid 12657 stack trace:
> > > reset_page_owner include/linux/page_owner.h:25 [inline]
> > > __free_pages_prepare mm/page_alloc.c:1397 [inline]
> > > __free_frozen_pages+0xc0d/0xd20 mm/page_alloc.c:2938
> > > __tlb_remove_table_free mm/mmu_gather.c:228 [inline]
> > > tlb_remove_table_rcu+0x85/0x100 mm/mmu_gather.c:291
> > > rcu_do_batch kernel/rcu/tree.c:2617 [inline]
> > > rcu_core+0x78b/0x10a0 kernel/rcu/tree.c:2869
> > > handle_softirqs+0x225/0x840 kernel/softirq.c:622
> > > __do_softirq kernel/softirq.c:656 [inline]
> > > invoke_softirq kernel/softirq.c:496 [inline]
> > > __irq_exit_rcu+0xca/0x220 kernel/softirq.c:735
> > > irq_exit_rcu+0x9/0x30 kernel/softirq.c:752
> > > instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1061 [inline]
> > > sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1061
> > > asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
> > >
> > > Memory state around the buggy address:
> > > ffff88804ec4c580: 00 00 00 fc fc fc fc fc fc fc fc fc fc fc fc fc
> > > ffff88804ec4c600: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > > >ffff88804ec4c680: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
> > > ^
> > > ffff88804ec4c700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> > > ffff88804ec4c780: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
> > > ==================================================================
> > >
> > >
> > > ---
> > > This report is generated by a bot. It may contain errors.
> > > See https://goo.gl/tpsmEJ for more information about syzbot.
> > > syzbot engineers can be reached at syzkaller@googlegroups.com.
> > >
> > > syzbot will keep track of this issue. See:
> > > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> > >
> > > If the report is already addressed, let syzbot know by replying with:
> > > #syz fix: exact-commit-title
> > >
> > > If you want to overwrite report's subsystems, reply with:
> > > #syz set subsystems: new-subsystem
> > > (See the list of subsystem names on the web dashboard)
> > >
> > > If the report is a duplicate of another one, reply with:
> > > #syz dup: exact-subject-of-another-report
> > >
> > > If you want to undo deduplication, reply with:
> > > #syz undup
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [syzbot] [net?] KASAN: slab-use-after-free Read in fib_rules_lookup
2026-06-16 17:06 ` Kuniyuki Iwashima
@ 2026-06-16 17:59 ` Kuniyuki Iwashima
0 siblings, 0 replies; 5+ messages in thread
From: Kuniyuki Iwashima @ 2026-06-16 17:59 UTC (permalink / raw)
To: kuniyu
Cc: davem, dsahern, edumazet, horms, idosch, kuba, linux-kernel,
netdev, pabeni, syzbot+965506b59a2de0b6905c, syzkaller-bugs
From: Kuniyuki Iwashima <kuniyu@google.com>
Date: Tue, 16 Jun 2026 10:06:55 -0700
> On Tue, Jun 16, 2026 at 8:55 AM Eric Dumazet <edumazet@google.com> wrote:
> >
> > On Tue, Jun 16, 2026 at 8:31 AM Ido Schimmel <idosch@nvidia.com> wrote:
> > >
> > > On Tue, Jun 16, 2026 at 07:05:24AM -0700, syzbot wrote:
> > > > Hello,
> > > >
> > > > syzbot found the following issue on:
> > > >
> > > > HEAD commit: 72dfa4700f78 net: dsa: sja1105: fix lastused timestamp in ..
> > >
> > > This includes commit 759923cf03b0 ("ipv4: fib: Convert
> > > fib_net_exit_batch() to ->exit_rtnl().") that moved ip_fib_net_exit()
> > > (and therefore fib4_rules_exit()) earlier in the netns dismantle path.
> > >
> > > Kuniyuki, can you please take a look?
> > >
> > > You can use this to reproduce:
> > >
> > > #!/bin/bash
> > >
> > > while true; do
> > > ip netns add ns1
> > > ip -n ns1 link set dev lo up
> > > ip -n ns1 address add 192.0.2.1/24 dev lo
> > > ip -n ns1 link add name dummy1 up type dummy
> > > ip -n ns1 address add 198.51.100.1/24 dev dummy1
> > > ip -n ns1 rule add ipproto tcp sport 12345 table 12345
> > > ip -n ns1 fou add port 5555 ipproto 47 local 192.0.2.1 peer 198.51.100.2 peer_port 54321
> > > ip netns del ns1
> > > done
> > >
> >
> > Oh right.
> >
> > While looking at this syzbot report I also found an old issue.
> >
> > https://lore.kernel.org/netdev/20260616141317.407791-1-edumazet@google.com/T/#u
> >
> > I guess adding some delays in enqueue_to_backlog() could trigger a
> > similar bug even if we revert Kuniyuki's patch.
>
> I'll look into it, thank you both !
I'll move fib4_rules_exit() to ->exit().
fib_unmerge() requires RTNL, but it is not needed in ->delete()
in the first place since it's already called in ->configure().
---8<---
diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index c7d1f31650d7..42212970d735 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -1612,10 +1612,6 @@ static void ip_fib_net_exit(struct net *net)
fib_free_table(tb);
}
}
-
-#ifdef CONFIG_IP_MULTIPLE_TABLES
- fib4_rules_exit(net);
-#endif
}
static int __net_init fib_net_init(struct net *net)
@@ -1652,6 +1648,9 @@ static int __net_init fib_net_init(struct net *net)
ip_fib_net_exit(net);
rtnl_net_unlock(net);
+#ifdef CONFIG_IP_MULTIPLE_TABLES
+ fib4_rules_exit(net);
+#endif
kfree(net->ipv4.fib_table_hash);
fib4_notifier_exit(net);
goto out;
@@ -1671,6 +1670,9 @@ static void __net_exit fib_net_exit_rtnl(struct net *net,
static void __net_exit fib_net_exit(struct net *net)
{
+#ifdef CONFIG_IP_MULTIPLE_TABLES
+ fib4_rules_exit(net);
+#endif
kfree(net->ipv4.fib_table_hash);
fib4_notifier_exit(net);
fib4_semantics_exit(net);
diff --git a/net/ipv4/fib_rules.c b/net/ipv4/fib_rules.c
index 51f0193092f0..0bf6204468c5 100644
--- a/net/ipv4/fib_rules.c
+++ b/net/ipv4/fib_rules.c
@@ -352,12 +352,6 @@ static int fib4_rule_configure(struct fib_rule *rule, struct sk_buff *skb,
static int fib4_rule_delete(struct fib_rule *rule)
{
struct net *net = rule->fr_net;
- int err;
-
- /* split local/main if they are not already split */
- err = fib_unmerge(net);
- if (err)
- goto errout;
#ifdef CONFIG_IP_ROUTE_CLASSID
if (((struct fib4_rule *)rule)->tclassid)
@@ -368,8 +362,8 @@ static int fib4_rule_delete(struct fib_rule *rule)
if (net->ipv4.fib_rules_require_fldissect &&
fib_rule_requires_fldissect(rule))
net->ipv4.fib_rules_require_fldissect--;
-errout:
- return err;
+
+ return 0;
}
static int fib4_rule_compare(struct fib_rule *rule, struct fib_rule_hdr *frh,
---8<---
>
> >
> >
> >
> >
> > > Thanks
> > >
> > > > git tree: net-next
> > > > console output: https://syzkaller.appspot.com/x/log.txt?x=15794bd2580000
> > > > kernel config: https://syzkaller.appspot.com/x/.config?x=a0842261b62cdea8
> > > > dashboard link: https://syzkaller.appspot.com/bug?extid=965506b59a2de0b6905c
> > > > compiler: Debian clang version 22.1.6 (++20260514074242+fc4aad7b5db3-1~exp1~20260514074407.73), Debian LLD 22.1.6
> > > >
> > > > Unfortunately, I don't have any reproducer for this issue yet.
> > > >
> > > > Downloadable assets:
> > > > disk image: https://storage.googleapis.com/syzbot-assets/d4e16f50a97c/disk-72dfa470.raw.xz
> > > > vmlinux: https://storage.googleapis.com/syzbot-assets/6cd4a736e796/vmlinux-72dfa470.xz
> > > > kernel image: https://storage.googleapis.com/syzbot-assets/548b0011c8e8/bzImage-72dfa470.xz
> > > >
> > > > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > > > Reported-by: syzbot+965506b59a2de0b6905c@syzkaller.appspotmail.com
> > > >
> > > > bond0 (unregistering): Released all slaves
> > > > bond1 (unregistering): Released all slaves
> > > > bond2 (unregistering): (slave dummy0): Releasing active interface
> > > > bond2 (unregistering): Released all slaves
> > > > ==================================================================
> > > > BUG: KASAN: slab-use-after-free in fib_rules_lookup+0x15e/0xeb0 net/core/fib_rules.c:321
> > > > Read of size 8 at addr ffff88804ec4c680 by task kworker/u8:21/12641
> > > >
> > > > CPU: 0 UID: 0 PID: 12641 Comm: kworker/u8:21 Not tainted syzkaller #0 PREEMPT(full)
> > > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
> > > > Workqueue: netns cleanup_net
> > > > Call Trace:
> > > > <TASK>
> > > > dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
> > > > print_address_description+0x55/0x1e0 mm/kasan/report.c:378
> > > > print_report+0x58/0x70 mm/kasan/report.c:482
> > > > kasan_report+0x117/0x150 mm/kasan/report.c:595
> > > > fib_rules_lookup+0x15e/0xeb0 net/core/fib_rules.c:321
> > > > __fib_lookup+0x106/0x210 net/ipv4/fib_rules.c:96
> > > > ip_route_output_key_hash_rcu+0x294/0x2720 net/ipv4/route.c:2811
> > > > ip_route_output_key_hash+0x18d/0x2a0 net/ipv4/route.c:2702
> > > > __ip_route_output_key include/net/route.h:169 [inline]
> > > > ip_route_output_flow+0x2a/0x150 net/ipv4/route.c:2929
> > > > ip4_datagram_release_cb+0x89d/0xbe0 net/ipv4/datagram.c:118
> > > > release_sock+0x206/0x260 net/core/sock.c:3861
> > > > inet_shutdown+0x2b1/0x390 net/ipv4/af_inet.c:950
> > > > udp_tunnel_sock_release+0x6d/0x80 net/ipv4/udp_tunnel_core.c:197
> > > > fou_release net/ipv4/fou_core.c:562 [inline]
> > > > fou_exit_net+0x17d/0x1f0 net/ipv4/fou_core.c:1230
> > > > ops_exit_list net/core/net_namespace.c:199 [inline]
> > > > ops_undo_list+0x43d/0x8d0 net/core/net_namespace.c:252
> > > > cleanup_net+0x572/0x810 net/core/net_namespace.c:702
> > > > process_one_work kernel/workqueue.c:3314 [inline]
> > > > process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3397
> > > > worker_thread+0xa47/0xfb0 kernel/workqueue.c:3478
> > > > kthread+0x389/0x470 kernel/kthread.c:436
> > > > ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
> > > > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
> > > > </TASK>
> > > >
> > > > Allocated by task 19121:
> > > > kasan_save_stack mm/kasan/common.c:57 [inline]
> > > > kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
> > > > poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
> > > > __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415
> > > > kasan_kmalloc include/linux/kasan.h:263 [inline]
> > > > __do_kmalloc_node mm/slub.c:5296 [inline]
> > > > __kmalloc_node_track_caller_noprof+0x4d7/0x7b0 mm/slub.c:5408
> > > > kmemdup_noprof+0x2b/0x70 mm/util.c:138
> > > > kmemdup_noprof include/linux/fortify-string.h:763 [inline]
> > > > fib_rules_register+0x2f/0x400 net/core/fib_rules.c:170
> > > > fib4_rules_init+0x21/0x160 net/ipv4/fib_rules.c:508
> > > > ip_fib_net_init net/ipv4/fib_frontend.c:1578 [inline]
> > > > fib_net_init+0x17a/0x3e0 net/ipv4/fib_frontend.c:1628
> > > > ops_init+0x35d/0x5d0 net/core/net_namespace.c:137
> > > > setup_net+0x118/0x350 net/core/net_namespace.c:446
> > > > copy_net_ns+0x4f9/0x720 net/core/net_namespace.c:579
> > > > create_new_namespaces+0x3f0/0x6b0 kernel/nsproxy.c:132
> > > > unshare_nsproxy_namespaces+0x149/0x190 kernel/nsproxy.c:234
> > > > ksys_unshare+0x57d/0xa00 kernel/fork.c:3242
> > > > __do_sys_unshare kernel/fork.c:3316 [inline]
> > > > __se_sys_unshare kernel/fork.c:3314 [inline]
> > > > __x64_sys_unshare+0x38/0x50 kernel/fork.c:3314
> > > > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> > > > do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
> > > > entry_SYSCALL_64_after_hwframe+0x77/0x7f
> > > >
> > > > Freed by task 12641:
> > > > kasan_save_stack mm/kasan/common.c:57 [inline]
> > > > kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
> > > > kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:584
> > > > poison_slab_object mm/kasan/common.c:253 [inline]
> > > > __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
> > > > kasan_slab_free include/linux/kasan.h:235 [inline]
> > > > slab_free_hook mm/slub.c:2689 [inline]
> > > > __rcu_free_sheaf_prepare+0x12d/0x2a0 mm/slub.c:2940
> > > > rcu_free_sheaf+0x31/0x200 mm/slub.c:5850
> > > > rcu_do_batch kernel/rcu/tree.c:2617 [inline]
> > > > rcu_core+0x78b/0x10a0 kernel/rcu/tree.c:2869
> > > > handle_softirqs+0x225/0x840 kernel/softirq.c:622
> > > > do_softirq+0x76/0xd0 kernel/softirq.c:523
> > > > __local_bh_enable_ip+0xf8/0x130 kernel/softirq.c:450
> > > > unregister_netdevice_many_notify+0x1874/0x2150 net/core/dev.c:12445
> > > > ops_exit_rtnl_list net/core/net_namespace.c:187 [inline]
> > > > ops_undo_list+0x391/0x8d0 net/core/net_namespace.c:248
> > > > cleanup_net+0x572/0x810 net/core/net_namespace.c:702
> > > > process_one_work kernel/workqueue.c:3314 [inline]
> > > > process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3397
> > > > worker_thread+0xa47/0xfb0 kernel/workqueue.c:3478
> > > > kthread+0x389/0x470 kernel/kthread.c:436
> > > > ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
> > > > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
> > > >
> > > > The buggy address belongs to the object at ffff88804ec4c600
> > > > which belongs to the cache kmalloc-192 of size 192
> > > > The buggy address is located 128 bytes inside of
> > > > freed 192-byte region [ffff88804ec4c600, ffff88804ec4c6c0)
> > > >
> > > > The buggy address belongs to the physical page:
> > > > page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x4ec4c
> > > > flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
> > > > page_type: f5(slab)
> > > > raw: 00fff00000000000 ffff88813fe163c0 dead000000000100 dead000000000122
> > > > raw: 0000000000000000 0000000800100010 00000000f5000000 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 0xd2cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 13856, tgid 13853 (syz.3.2144), ts 351172300879, free_ts 351133053454
> > > > set_page_owner include/linux/page_owner.h:32 [inline]
> > > > post_alloc_hook+0x22d/0x280 mm/page_alloc.c:1853
> > > > prep_new_page mm/page_alloc.c:1861 [inline]
> > > > get_page_from_freelist+0x24ae/0x2530 mm/page_alloc.c:3941
> > > > __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5221
> > > > alloc_slab_page mm/slub.c:3278 [inline]
> > > > allocate_slab+0x77/0x660 mm/slub.c:3467
> > > > new_slab mm/slub.c:3525 [inline]
> > > > refill_objects+0x336/0x3d0 mm/slub.c:7272
> > > > refill_sheaf mm/slub.c:2816 [inline]
> > > > __pcs_replace_empty_main+0x320/0x720 mm/slub.c:4652
> > > > alloc_from_pcs mm/slub.c:4750 [inline]
> > > > slab_alloc_node mm/slub.c:4884 [inline]
> > > > __do_kmalloc_node mm/slub.c:5295 [inline]
> > > > __kmalloc_noprof+0x464/0x750 mm/slub.c:5308
> > > > kmalloc_noprof include/linux/slab.h:954 [inline]
> > > > kzalloc_noprof include/linux/slab.h:1188 [inline]
> > > > new_dir fs/proc/proc_sysctl.c:966 [inline]
> > > > get_subdir fs/proc/proc_sysctl.c:1010 [inline]
> > > > sysctl_mkdir_p fs/proc/proc_sysctl.c:1320 [inline]
> > > > __register_sysctl_table+0xc02/0x1370 fs/proc/proc_sysctl.c:1395
> > > > neigh_sysctl_register+0x9b1/0xa90 net/core/neighbour.c:3915
> > > > addrconf_sysctl_register+0xb3/0x1c0 net/ipv6/addrconf.c:7396
> > > > ipv6_add_dev+0xd26/0x13a0 net/ipv6/addrconf.c:460
> > > > addrconf_notify+0x771/0x1050 net/ipv6/addrconf.c:3679
> > > > notifier_call_chain+0x1a5/0x3d0 kernel/notifier.c:85
> > > > call_netdevice_notifiers_extack net/core/dev.c:2288 [inline]
> > > > call_netdevice_notifiers net/core/dev.c:2302 [inline]
> > > > register_netdevice+0x18db/0x1f00 net/core/dev.c:11474
> > > > macsec_newlink+0x706/0x1200 drivers/net/macsec.c:4218
> > > > rtnl_newlink_create+0x310/0xb00 net/core/rtnetlink.c:3905
> > > > page last free pid 12657 tgid 12657 stack trace:
> > > > reset_page_owner include/linux/page_owner.h:25 [inline]
> > > > __free_pages_prepare mm/page_alloc.c:1397 [inline]
> > > > __free_frozen_pages+0xc0d/0xd20 mm/page_alloc.c:2938
> > > > __tlb_remove_table_free mm/mmu_gather.c:228 [inline]
> > > > tlb_remove_table_rcu+0x85/0x100 mm/mmu_gather.c:291
> > > > rcu_do_batch kernel/rcu/tree.c:2617 [inline]
> > > > rcu_core+0x78b/0x10a0 kernel/rcu/tree.c:2869
> > > > handle_softirqs+0x225/0x840 kernel/softirq.c:622
> > > > __do_softirq kernel/softirq.c:656 [inline]
> > > > invoke_softirq kernel/softirq.c:496 [inline]
> > > > __irq_exit_rcu+0xca/0x220 kernel/softirq.c:735
> > > > irq_exit_rcu+0x9/0x30 kernel/softirq.c:752
> > > > instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1061 [inline]
> > > > sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1061
> > > > asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
> > > >
> > > > Memory state around the buggy address:
> > > > ffff88804ec4c580: 00 00 00 fc fc fc fc fc fc fc fc fc fc fc fc fc
> > > > ffff88804ec4c600: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > > > >ffff88804ec4c680: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
> > > > ^
> > > > ffff88804ec4c700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> > > > ffff88804ec4c780: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
> > > > ==================================================================
> > > >
> > > >
> > > > ---
> > > > This report is generated by a bot. It may contain errors.
> > > > See https://goo.gl/tpsmEJ for more information about syzbot.
> > > > syzbot engineers can be reached at syzkaller@googlegroups.com.
> > > >
> > > > syzbot will keep track of this issue. See:
> > > > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> > > >
> > > > If the report is already addressed, let syzbot know by replying with:
> > > > #syz fix: exact-commit-title
> > > >
> > > > If you want to overwrite report's subsystems, reply with:
> > > > #syz set subsystems: new-subsystem
> > > > (See the list of subsystem names on the web dashboard)
> > > >
> > > > If the report is a duplicate of another one, reply with:
> > > > #syz dup: exact-subject-of-another-report
> > > >
> > > > If you want to undo deduplication, reply with:
> > > > #syz undup
>
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end of thread, other threads:[~2026-06-16 17:59 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-06-16 14:05 [syzbot] [net?] KASAN: slab-use-after-free Read in fib_rules_lookup syzbot
2026-06-16 15:31 ` Ido Schimmel
2026-06-16 15:55 ` Eric Dumazet
2026-06-16 17:06 ` Kuniyuki Iwashima
2026-06-16 17:59 ` Kuniyuki Iwashima
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