[syzbot] [hams?] KASAN: slab-use-after-free Read in rose_get_neigh

[syzbot] [hams?] KASAN: slab-use-after-free Read in rose_get_neigh

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    bb678f01804c Merge branch 'intel-wired-lan-driver-updates-..
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=15ddd8ee980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=ce6b8d38d53fa4e
dashboard link: https://syzkaller.appspot.com/bug?extid=e04e2c007ba2c80476cb
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a34378d9338a/disk-bb678f01.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9ac7eb354351/vmlinux-bb678f01.xz
kernel image: https://storage.googleapis.com/syzbot-assets/49fdcb908144/bzImage-bb678f01.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e04e2c007ba2c80476cb@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-use-after-free in rose_get_neigh+0x1b6/0x6f0 net/rose/rose_route.c:692
Read of size 1 at addr ffff88802a32b030 by task syz-executor.2/6399

CPU: 0 PID: 6399 Comm: syz-executor.2 Not tainted 6.10.0-rc2-syzkaller-00722-gbb678f01804c #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
 print_address_description mm/kasan/report.c:377 [inline]
 print_report+0x169/0x550 mm/kasan/report.c:488
 kasan_report+0x143/0x180 mm/kasan/report.c:601
 rose_get_neigh+0x1b6/0x6f0 net/rose/rose_route.c:692
 rose_connect+0x45a/0x1170 net/rose/af_rose.c:808
 __sys_connect_file net/socket.c:2049 [inline]
 __sys_connect+0x2df/0x310 net/socket.c:2066
 __do_sys_connect net/socket.c:2076 [inline]
 __se_sys_connect net/socket.c:2073 [inline]
 __x64_sys_connect+0x7a/0x90 net/socket.c:2073
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7feee447cf69
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 90 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007feee51920c8 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 00007feee45b3f80 RCX: 00007feee447cf69
RDX: 000000000000001c RSI: 00000000200002c0 RDI: 0000000000000007
RBP: 00007feee44da6fe R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007feee45b3f80 R15: 00007ffd3499d388
 </TASK>

Allocated by task 29561:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
 poison_kmalloc_redzone mm/kasan/common.c:370 [inline]
 __kasan_kmalloc+0x98/0xb0 mm/kasan/common.c:387
 kasan_kmalloc include/linux/kasan.h:211 [inline]
 kmalloc_trace_noprof+0x19c/0x2c0 mm/slub.c:4152
 kmalloc_noprof include/linux/slab.h:660 [inline]
 batadv_forw_packet_alloc+0x19c/0x3b0 net/batman-adv/send.c:519
 batadv_iv_ogm_aggregate_new net/batman-adv/bat_iv_ogm.c:562 [inline]
 batadv_iv_ogm_queue_add+0x6da/0xbf0 net/batman-adv/bat_iv_ogm.c:670
 batadv_iv_ogm_schedule_buff net/batman-adv/bat_iv_ogm.c:849 [inline]
 batadv_iv_ogm_schedule+0xc4d/0x1090 net/batman-adv/bat_iv_ogm.c:868
 batadv_iv_send_outstanding_bat_ogm_packet+0x6fe/0x810 net/batman-adv/bat_iv_ogm.c:1712
 process_one_work kernel/workqueue.c:3231 [inline]
 process_scheduled_works+0xa2c/0x1830 kernel/workqueue.c:3312
 worker_thread+0x86d/0xd70 kernel/workqueue.c:3393
 kthread+0x2f0/0x390 kernel/kthread.c:389
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Freed by task 29551:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
 kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:579
 poison_slab_object+0xe0/0x150 mm/kasan/common.c:240
 __kasan_slab_free+0x37/0x60 mm/kasan/common.c:256
 kasan_slab_free include/linux/kasan.h:184 [inline]
 slab_free_hook mm/slub.c:2195 [inline]
 slab_free mm/slub.c:4436 [inline]
 kfree+0x149/0x360 mm/slub.c:4557
 process_one_work kernel/workqueue.c:3231 [inline]
 process_scheduled_works+0xa2c/0x1830 kernel/workqueue.c:3312
 worker_thread+0x86d/0xd70 kernel/workqueue.c:3393
 kthread+0x2f0/0x390 kernel/kthread.c:389
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Last potentially related work creation:
 kasan_save_stack+0x3f/0x60 mm/kasan/common.c:47
 __kasan_record_aux_stack+0xac/0xc0 mm/kasan/generic.c:541
 insert_work+0x3e/0x330 kernel/workqueue.c:2207
 __queue_work+0xc16/0xee0 kernel/workqueue.c:2359
 call_timer_fn+0x18e/0x650 kernel/time/timer.c:1792
 expire_timers kernel/time/timer.c:1838 [inline]
 __run_timers kernel/time/timer.c:2417 [inline]
 __run_timer_base+0x695/0x8e0 kernel/time/timer.c:2428
 run_timer_base kernel/time/timer.c:2437 [inline]
 run_timer_softirq+0xb7/0x170 kernel/time/timer.c:2447
 handle_softirqs+0x2c4/0x970 kernel/softirq.c:554
 __do_softirq kernel/softirq.c:588 [inline]
 invoke_softirq kernel/softirq.c:428 [inline]
 __irq_exit_rcu+0xf4/0x1c0 kernel/softirq.c:637
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:649
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1043 [inline]
 sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1043
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702

The buggy address belongs to the object at ffff88802a32b000
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 48 bytes inside of
 freed 512-byte region [ffff88802a32b000, ffff88802a32b200)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2a328
head: order:2 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffefff(slab)
raw: 00fff00000000040 ffff888015041c80 dead000000000100 dead000000000122
raw: 0000000000000000 0000000000100010 00000001ffffefff 0000000000000000
head: 00fff00000000040 ffff888015041c80 dead000000000100 dead000000000122
head: 0000000000000000 0000000000100010 00000001ffffefff 0000000000000000
head: 00fff00000000002 ffffea0000a8ca01 ffffffffffffffff 0000000000000000
head: 0000000000000004 0000000000000000 00000000ffffffff 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5114, tgid 5114 (syz-executor.2), ts 77337016652, free_ts 77201339167
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f3/0x230 mm/page_alloc.c:1468
 prep_new_page mm/page_alloc.c:1476 [inline]
 get_page_from_freelist+0x2e2d/0x2ee0 mm/page_alloc.c:3402
 __alloc_pages_noprof+0x256/0x6c0 mm/page_alloc.c:4660
 __alloc_pages_node_noprof include/linux/gfp.h:269 [inline]
 alloc_pages_node_noprof include/linux/gfp.h:296 [inline]
 alloc_slab_page+0x5f/0x120 mm/slub.c:2264
 allocate_slab+0x5a/0x2e0 mm/slub.c:2427
 new_slab mm/slub.c:2480 [inline]
 ___slab_alloc+0xcd1/0x14b0 mm/slub.c:3666
 __slab_alloc+0x58/0xa0 mm/slub.c:3756
 __slab_alloc_node mm/slub.c:3809 [inline]
 slab_alloc_node mm/slub.c:3988 [inline]
 kmalloc_trace_noprof+0x1d5/0x2c0 mm/slub.c:4147
 kmalloc_noprof include/linux/slab.h:660 [inline]
 kzalloc_noprof include/linux/slab.h:778 [inline]
 device_private_init drivers/base/core.c:3566 [inline]
 device_add+0xc1/0xbf0 drivers/base/core.c:3617
 netdev_register_kobject+0x17e/0x320 net/core/net-sysfs.c:2136
 register_netdevice+0x11d5/0x19e0 net/core/dev.c:10375
 veth_newlink+0x84f/0xcd0 drivers/net/veth.c:1860
 rtnl_newlink_create net/core/rtnetlink.c:3510 [inline]
 __rtnl_newlink net/core/rtnetlink.c:3730 [inline]
 rtnl_newlink+0x158f/0x20a0 net/core/rtnetlink.c:3743
 rtnetlink_rcv_msg+0x89b/0x1180 net/core/rtnetlink.c:6641
 netlink_rcv_skb+0x1e3/0x430 net/netlink/af_netlink.c:2550
 netlink_unicast_kernel net/netlink/af_netlink.c:1331 [inline]
 netlink_unicast+0x7ea/0x980 net/netlink/af_netlink.c:1357
page last free pid 5125 tgid 5125 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1088 [inline]
 free_unref_page+0xd22/0xea0 mm/page_alloc.c:2565
 discard_slab mm/slub.c:2526 [inline]
 __put_partials+0xeb/0x130 mm/slub.c:2994
 put_cpu_partial+0x17c/0x250 mm/slub.c:3069
 __slab_free+0x2ea/0x3d0 mm/slub.c:4306
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x9e/0x140 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x14f/0x170 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x23/0x80 mm/kasan/common.c:322
 kasan_slab_alloc include/linux/kasan.h:201 [inline]
 slab_post_alloc_hook mm/slub.c:3940 [inline]
 slab_alloc_node mm/slub.c:4000 [inline]
 kmalloc_trace_noprof+0x132/0x2c0 mm/slub.c:4147
 kmalloc_noprof include/linux/slab.h:660 [inline]
 netdevice_queue_work drivers/infiniband/core/roce_gid_mgmt.c:642 [inline]
 netdevice_event+0x37d/0x950 drivers/infiniband/core/roce_gid_mgmt.c:801
 notifier_call_chain+0x19f/0x3e0 kernel/notifier.c:93
 __netdev_upper_dev_link+0x4c3/0x670 net/core/dev.c:7888
 netdev_master_upper_dev_link+0xb1/0x100 net/core/dev.c:7958
 batadv_hardif_enable_interface+0x26e/0x9f0 net/batman-adv/hard-interface.c:734
 batadv_softif_slave_add+0x79/0xf0 net/batman-adv/soft-interface.c:844
 do_set_master net/core/rtnetlink.c:2701 [inline]
 do_setlink+0xe70/0x41f0 net/core/rtnetlink.c:2907
 __rtnl_newlink net/core/rtnetlink.c:3696 [inline]
 rtnl_newlink+0x180b/0x20a0 net/core/rtnetlink.c:3743



---
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Re: [syzbot] [hams?] KASAN: slab-use-after-free Read in rose_get_neigh

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit:    9d7a0577c9db gcc-15: disable '-Wunterminated-string-initia..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=139b5ccc580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=efa83f9a6dd67d67
dashboard link: https://syzkaller.appspot.com/bug?extid=e04e2c007ba2c80476cb
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15652c70580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17676c70580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/97d5bc2781eb/disk-9d7a0577.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/25887608b61e/vmlinux-9d7a0577.xz
kernel image: https://storage.googleapis.com/syzbot-assets/505d68dbd87d/bzImage-9d7a0577.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e04e2c007ba2c80476cb@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-use-after-free in rose_get_neigh+0x549/0x640 net/rose/rose_route.c:692
Read of size 1 at addr ffff888036f04c30 by task syz-executor234/6532

CPU: 0 UID: 0 PID: 6532 Comm: syz-executor234 Not tainted 6.15.0-rc3-syzkaller-00001-g9d7a0577c9db #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:408 [inline]
 print_report+0xc3/0x670 mm/kasan/report.c:521
 kasan_report+0xe0/0x110 mm/kasan/report.c:634
 rose_get_neigh+0x549/0x640 net/rose/rose_route.c:692
 rose_connect+0x2d4/0x1540 net/rose/af_rose.c:816
 __sys_connect_file+0x13e/0x1a0 net/socket.c:2038
 __sys_connect+0x14d/0x170 net/socket.c:2057
 __do_sys_connect net/socket.c:2063 [inline]
 __se_sys_connect net/socket.c:2060 [inline]
 __x64_sys_connect+0x72/0xb0 net/socket.c:2060
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb5b7a9cc29
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 91 1f 00 00 90 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fb5b7223168 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 00007fb5b7b22438 RCX: 00007fb5b7a9cc29
RDX: 0000000000000040 RSI: 0000200000000040 RDI: 0000000000000006
RBP: 00007fb5b7b22430 R08: 00007fb5b72236c0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fb5b7b2243c
R13: 000000000000006e R14: 00007ffe0d8e5c80 R15: 00007ffe0d8e5d68
 </TASK>

Allocated by task 5886:
 kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
 kasan_save_track+0x14/0x30 mm/kasan/common.c:68
 poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:394
 kmalloc_noprof include/linux/slab.h:905 [inline]
 rose_add_node net/rose/rose_route.c:85 [inline]
 rose_rt_ioctl+0x87e/0x1d40 net/rose/rose_route.c:747
 rose_ioctl+0x64d/0x7d0 net/rose/af_rose.c:1380
 sock_do_ioctl+0x115/0x280 net/socket.c:1190
 sock_ioctl+0x227/0x6b0 net/socket.c:1311
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:906 [inline]
 __se_sys_ioctl fs/ioctl.c:892 [inline]
 __x64_sys_ioctl+0x190/0x200 fs/ioctl.c:892
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 6532:
 kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
 kasan_save_track+0x14/0x30 mm/kasan/common.c:68
 kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:576
 poison_slab_object mm/kasan/common.c:247 [inline]
 __kasan_slab_free+0x51/0x70 mm/kasan/common.c:264
 kasan_slab_free include/linux/kasan.h:233 [inline]
 slab_free_hook mm/slub.c:2398 [inline]
 slab_free mm/slub.c:4656 [inline]
 kfree+0x2b6/0x4d0 mm/slub.c:4855
 rose_remove_neigh+0x25e/0x370 net/rose/rose_route.c:240
 rose_rt_device_down+0x2aa/0x390 net/rose/rose_route.c:522
 rose_device_event+0xfc/0x120 net/rose/af_rose.c:248
 notifier_call_chain+0xb9/0x410 kernel/notifier.c:85
 call_netdevice_notifiers_info+0xbe/0x140 net/core/dev.c:2176
 call_netdevice_notifiers_extack net/core/dev.c:2214 [inline]
 call_netdevice_notifiers net/core/dev.c:2228 [inline]
 __dev_notify_flags+0x1f7/0x2e0 net/core/dev.c:9407
 netif_change_flags+0x108/0x160 net/core/dev.c:9434
 dev_change_flags+0xba/0x250 net/core/dev_api.c:68
 dev_ifsioc+0x1498/0x1f70 net/core/dev_ioctl.c:565
 dev_ioctl+0x223/0x10e0 net/core/dev_ioctl.c:821
 sock_do_ioctl+0x19d/0x280 net/socket.c:1204
 sock_ioctl+0x227/0x6b0 net/socket.c:1311
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:906 [inline]
 __se_sys_ioctl fs/ioctl.c:892 [inline]
 __x64_sys_ioctl+0x190/0x200 fs/ioctl.c:892
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888036f04c00
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 48 bytes inside of
 freed 512-byte region [ffff888036f04c00, ffff888036f04e00)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x36f04
head: order:2 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801b441c80 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801b441c80 dead000000000122 0000000000000000
head: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
head: 00fff00000000002 ffffea0000dbc101 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000004
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5825, tgid 5825 (syz-executor234), ts 69568665808, free_ts 69397287194
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x181/0x1b0 mm/page_alloc.c:1718
 prep_new_page mm/page_alloc.c:1726 [inline]
 get_page_from_freelist+0x135c/0x3920 mm/page_alloc.c:3688
 __alloc_frozen_pages_noprof+0x263/0x23a0 mm/page_alloc.c:4970
 alloc_pages_mpol+0x1fb/0x550 mm/mempolicy.c:2301
 alloc_slab_page mm/slub.c:2468 [inline]
 allocate_slab mm/slub.c:2632 [inline]
 new_slab+0x244/0x340 mm/slub.c:2686
 ___slab_alloc+0xd9c/0x1940 mm/slub.c:3872
 __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3962
 __slab_alloc_node mm/slub.c:4037 [inline]
 slab_alloc_node mm/slub.c:4198 [inline]
 __do_kmalloc_node mm/slub.c:4340 [inline]
 __kmalloc_noprof+0x2f2/0x510 mm/slub.c:4353
 kmalloc_noprof include/linux/slab.h:909 [inline]
 kzalloc_noprof include/linux/slab.h:1039 [inline]
 fib6_info_alloc+0x40/0x160 net/ipv6/ip6_fib.c:155
 ip6_route_info_create+0x33f/0x18e0 net/ipv6/route.c:3802
 addrconf_f6i_alloc+0x391/0x670 net/ipv6/route.c:4631
 ipv6_add_addr+0x531/0x1fe0 net/ipv6/addrconf.c:1121
 inet6_addr_add+0x256/0x960 net/ipv6/addrconf.c:3049
 inet6_rtm_newaddr+0x1619/0x1c70 net/ipv6/addrconf.c:5060
 rtnetlink_rcv_msg+0x95b/0xe90 net/core/rtnetlink.c:6955
 netlink_rcv_skb+0x16a/0x440 net/netlink/af_netlink.c:2534
page last free pid 5827 tgid 5827 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1262 [inline]
 __free_frozen_pages+0x69d/0xff0 mm/page_alloc.c:2725
 discard_slab mm/slub.c:2730 [inline]
 __put_partials+0x16d/0x1c0 mm/slub.c:3199
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x4e/0x120 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x195/0x1e0 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x69/0x90 mm/kasan/common.c:329
 kasan_slab_alloc include/linux/kasan.h:250 [inline]
 slab_post_alloc_hook mm/slub.c:4161 [inline]
 slab_alloc_node mm/slub.c:4210 [inline]
 __kmalloc_cache_noprof+0x1f1/0x3e0 mm/slub.c:4367
 kmalloc_noprof include/linux/slab.h:905 [inline]
 netdevice_queue_work drivers/infiniband/core/roce_gid_mgmt.c:664 [inline]
 netdevice_event+0x365/0x9d0 drivers/infiniband/core/roce_gid_mgmt.c:823
 notifier_call_chain+0xb9/0x410 kernel/notifier.c:85
 call_netdevice_notifiers_info+0xbe/0x140 net/core/dev.c:2176
 call_netdevice_notifiers_extack net/core/dev.c:2214 [inline]
 call_netdevice_notifiers net/core/dev.c:2228 [inline]
 netif_set_mac_address+0x378/0x4a0 net/core/dev.c:9601
 do_setlink.constprop.0+0x9f1/0x44b0 net/core/rtnetlink.c:3103
 rtnl_changelink net/core/rtnetlink.c:3769 [inline]
 __rtnl_newlink net/core/rtnetlink.c:3928 [inline]
 rtnl_newlink+0x1446/0x2000 net/core/rtnetlink.c:4065
 rtnetlink_rcv_msg+0x95b/0xe90 net/core/rtnetlink.c:6955
 netlink_rcv_skb+0x16a/0x440 net/netlink/af_netlink.c:2534
 netlink_unicast_kernel net/netlink/af_netlink.c:1313 [inline]
 netlink_unicast+0x53a/0x7f0 net/netlink/af_netlink.c:1339
 netlink_sendmsg+0x8d1/0xdd0 net/netlink/af_netlink.c:1883

Memory state around the buggy address:
 ffff888036f04b00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888036f04b80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888036f04c00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                     ^
 ffff888036f04c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888036f04d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

Re: [syzbot] [hams?] KASAN: slab-use-after-free Read in rose_get_neigh

[Kohei Enju]

#syz test

diff --git a/net/rose/rose_route.c b/net/rose/rose_route.c
index 2dd6bd3a3011..a85969e2369f 100644
--- a/net/rose/rose_route.c
+++ b/net/rose/rose_route.c
@@ -480,6 +480,7 @@ void rose_rt_device_down(struct net_device *dev)
 	struct rose_neigh *s, *rose_neigh;
 	struct rose_node  *t, *rose_node;
 	int i;
+	unsigned char old_count;
 
 	spin_lock_bh(&rose_node_list_lock);
 	spin_lock_bh(&rose_neigh_list_lock);
@@ -497,7 +498,8 @@ void rose_rt_device_down(struct net_device *dev)
 			t         = rose_node;
 			rose_node = rose_node->next;
 
-			for (i = 0; i < t->count; i++) {
+			old_count = t->count;
+			for (i = 0; i < old_count; i++) {
 				if (t->neighbour[i] != s)
 					continue;
 

Re: [syzbot] [hams?] KASAN: slab-use-after-free Read in rose_get_neigh

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+e04e2c007ba2c80476cb@syzkaller.appspotmail.com
Tested-by: syzbot+e04e2c007ba2c80476cb@syzkaller.appspotmail.com

Tested on:

commit:         78f4e737 Merge tag 'for-6.16/dm-fixes' of git://git.ke..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=157e6b70580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4ec8b4e4d31ae914
dashboard link: https://syzkaller.appspot.com/bug?extid=e04e2c007ba2c80476cb
compiler:       Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6
patch:          https://syzkaller.appspot.com/x/patch.diff?x=140b470c580000

Note: testing is done by a robot and is best-effort only.

Re: [syzbot] [hams?] KASAN: slab-use-after-free Read in rose_get_neigh

[Kohei Enju]

#syz test

diff --git a/net/rose/rose_route.c b/net/rose/rose_route.c
index 2dd6bd3a3011..a488fd8c4710 100644
--- a/net/rose/rose_route.c
+++ b/net/rose/rose_route.c
@@ -479,7 +479,7 @@ void rose_rt_device_down(struct net_device *dev)
 {
 	struct rose_neigh *s, *rose_neigh;
 	struct rose_node  *t, *rose_node;
-	int i;
+	int i, j;
 
 	spin_lock_bh(&rose_node_list_lock);
 	spin_lock_bh(&rose_neigh_list_lock);
@@ -497,22 +497,14 @@ void rose_rt_device_down(struct net_device *dev)
 			t         = rose_node;
 			rose_node = rose_node->next;
 
-			for (i = 0; i < t->count; i++) {
+			for (i = t->count - 1; i >= 0; i--) {
 				if (t->neighbour[i] != s)
 					continue;
 
 				t->count--;
 
-				switch (i) {
-				case 0:
-					t->neighbour[0] = t->neighbour[1];
-					fallthrough;
-				case 1:
-					t->neighbour[1] = t->neighbour[2];
-					break;
-				case 2:
-					break;
-				}
+				for (j = i; j < t->count; j++)
+					t->neighbour[j] = t->neighbour[j + 1];
 			}
 
 			if (t->count <= 0)

Re: [syzbot] [hams?] KASAN: slab-use-after-free Read in rose_get_neigh

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+e04e2c007ba2c80476cb@syzkaller.appspotmail.com
Tested-by: syzbot+e04e2c007ba2c80476cb@syzkaller.appspotmail.com

Tested on:

commit:         7595b66a Merge tag 'selinux-pr-20250624' of git://git...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14204f0c580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4ec8b4e4d31ae914
dashboard link: https://syzkaller.appspot.com/bug?extid=e04e2c007ba2c80476cb
compiler:       Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6
patch:          https://syzkaller.appspot.com/x/patch.diff?x=1469b70c580000

Note: testing is done by a robot and is best-effort only.

Re: [syzbot] [hams?] KASAN: slab-use-after-free Read in rose_get_neigh

[Hillf Danton]

> Date: Mon, 21 Apr 2025 19:40:26 -0700
> syzbot has found a reproducer for the following issue on:
> 
> HEAD commit:    9d7a0577c9db gcc-15: disable '-Wunterminated-string-initia..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=139b5ccc580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=efa83f9a6dd67d67
> dashboard link: https://syzkaller.appspot.com/bug?extid=e04e2c007ba2c80476cb
> compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15652c70580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17676c70580000

#syz test upstream master

--- x/net/rose/rose_route.c
+++ y/net/rose/rose_route.c
@@ -500,6 +500,7 @@ void rose_rt_device_down(struct net_devi
 			for (i = 0; i < t->count; i++) {
 				if (t->neighbour[i] != s)
 					continue;
+				t->neighbour[i] = NULL;
 
 				t->count--;
 
@@ -689,6 +690,8 @@ struct rose_neigh *rose_get_neigh(rose_a
 	for (node = rose_node_list; node != NULL; node = node->next) {
 		if (rosecmpm(addr, &node->address, node->mask) == 0) {
 			for (i = 0; i < node->count; i++) {
+				if (!node->neighbour[i])
+					continue;
 				if (node->neighbour[i]->restarted) {
 					res = node->neighbour[i];
 					goto out;
@@ -700,6 +703,8 @@ struct rose_neigh *rose_get_neigh(rose_a
 		for (node = rose_node_list; node != NULL; node = node->next) {
 			if (rosecmpm(addr, &node->address, node->mask) == 0) {
 				for (i = 0; i < node->count; i++) {
+					if (!node->neighbour[i])
+						continue;
 					if (!rose_ftimer_running(node->neighbour[i])) {
 						res = node->neighbour[i];
 						goto out;
--

Re: [syzbot] [hams?] KASAN: slab-use-after-free Read in rose_get_neigh

[syzbot]

Hello,

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

==================================================================
BUG: KASAN: slab-use-after-free in rose_get_neigh+0x48e/0xb20 net/rose/rose_route.c:695
Read of size 1 at addr ffff8880287d5430 by task syz.1.592/8046

CPU: 1 UID: 0 PID: 8046 Comm: syz.1.592 Not tainted 6.16.0-rc3-syzkaller-g7595b66ae9de-dirty #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:408 [inline]
 print_report+0xd2/0x2b0 mm/kasan/report.c:521
 kasan_report+0x118/0x150 mm/kasan/report.c:634
 rose_get_neigh+0x48e/0xb20 net/rose/rose_route.c:695
 rose_connect+0x416/0x10a0 net/rose/af_rose.c:816
 __sys_connect_file net/socket.c:2038 [inline]
 __sys_connect+0x313/0x440 net/socket.c:2057
 __do_sys_connect net/socket.c:2063 [inline]
 __se_sys_connect net/socket.c:2060 [inline]
 __x64_sys_connect+0x7a/0x90 net/socket.c:2060
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f04d738e969
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f04d820b038 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 00007f04d75b5fa0 RCX: 00007f04d738e969
RDX: 000000000000001c RSI: 0000200000000040 RDI: 0000000000000008
RBP: 00007f04d7410ab1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f04d75b5fa0 R15: 00007fffa69f4f58
 </TASK>

Allocated by task 6760:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
 poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:394
 kasan_kmalloc include/linux/kasan.h:260 [inline]
 __kmalloc_cache_noprof+0x230/0x3d0 mm/slub.c:4359
 kmalloc_noprof include/linux/slab.h:905 [inline]
 rose_add_node+0x23a/0xde0 net/rose/rose_route.c:85
 rose_rt_ioctl+0xa48/0xfb0 net/rose/rose_route.c:752
 rose_ioctl+0x3ce/0x8b0 net/rose/af_rose.c:1380
 sock_do_ioctl+0xd9/0x300 net/socket.c:1190
 sock_ioctl+0x576/0x790 net/socket.c:1311
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:907 [inline]
 __se_sys_ioctl+0xf9/0x170 fs/ioctl.c:893
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 8049:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:576
 poison_slab_object mm/kasan/common.c:247 [inline]
 __kasan_slab_free+0x62/0x70 mm/kasan/common.c:264
 kasan_slab_free include/linux/kasan.h:233 [inline]
 slab_free_hook mm/slub.c:2381 [inline]
 slab_free mm/slub.c:4643 [inline]
 kfree+0x18e/0x440 mm/slub.c:4842
 rose_rt_device_down+0x5e1/0x630 net/rose/rose_route.c:523
 rose_device_event+0x603/0x6a0 net/rose/af_rose.c:248
 notifier_call_chain+0x1b3/0x3e0 kernel/notifier.c:85
 call_netdevice_notifiers_extack net/core/dev.c:2268 [inline]
 call_netdevice_notifiers net/core/dev.c:2282 [inline]
 __dev_notify_flags+0x18d/0x2e0 net/core/dev.c:-1
 netif_change_flags+0xe8/0x1a0 net/core/dev.c:9526
 dev_change_flags+0x130/0x260 net/core/dev_api.c:68
 dev_ioctl+0x7b4/0x1150 net/core/dev_ioctl.c:823
 sock_do_ioctl+0x22c/0x300 net/socket.c:1204
 sock_ioctl+0x576/0x790 net/socket.c:1311
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:907 [inline]
 __se_sys_ioctl+0xf9/0x170 fs/ioctl.c:893
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff8880287d5400
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 48 bytes inside of
 freed 512-byte region [ffff8880287d5400, ffff8880287d5600)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff8880287d5800 pfn:0x287d4
head: order:2 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000240(workingset|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000240 ffff88801a441c80 ffffea00016abd10 ffffea0000a3c510
raw: ffff8880287d5800 000000000010000e 00000000f5000000 0000000000000000
head: 00fff00000000240 ffff88801a441c80 ffffea00016abd10 ffffea0000a3c510
head: ffff8880287d5800 000000000010000e 00000000f5000000 0000000000000000
head: 00fff00000000002 ffffea0000a1f501 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000004
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 13836989135, free_ts 0
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x240/0x2a0 mm/page_alloc.c:1704
 prep_new_page mm/page_alloc.c:1712 [inline]
 get_page_from_freelist+0x21d5/0x22b0 mm/page_alloc.c:3669
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:4959
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2419
 alloc_slab_page mm/slub.c:2451 [inline]
 allocate_slab+0x8a/0x3b0 mm/slub.c:2619
 new_slab mm/slub.c:2673 [inline]
 ___slab_alloc+0xbfc/0x1480 mm/slub.c:3859
 __slab_alloc mm/slub.c:3949 [inline]
 __slab_alloc_node mm/slub.c:4024 [inline]
 slab_alloc_node mm/slub.c:4185 [inline]
 __kmalloc_cache_noprof+0x296/0x3d0 mm/slub.c:4354
 kmalloc_noprof include/linux/slab.h:905 [inline]
 kmalloc_array_noprof include/linux/slab.h:948 [inline]
 dev_pm_qos_constraints_allocate+0x8f/0x3f0 drivers/base/power/qos.c:205
 __dev_pm_qos_add_request+0x123/0x4c0 drivers/base/power/qos.c:345
 dev_pm_qos_add_request+0x36/0x60 drivers/base/power/qos.c:395
 usb_hub_create_port_device+0x48f/0xb90 drivers/usb/core/port.c:783
 hub_configure drivers/usb/core/hub.c:1711 [inline]
 hub_probe+0x25af/0x36e0 drivers/usb/core/hub.c:1977
 usb_probe_interface+0x641/0xbc0 drivers/usb/core/driver.c:396
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x26a/0x9a0 drivers/base/dd.c:657
 __driver_probe_device+0x18c/0x2f0 drivers/base/dd.c:799
 driver_probe_device+0x4f/0x430 drivers/base/dd.c:829
page_owner free stack trace missing

Memory state around the buggy address:
 ffff8880287d5300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880287d5380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880287d5400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                     ^
 ffff8880287d5480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880287d5500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


Tested on:

commit:         7595b66a Merge tag 'selinux-pr-20250624' of git://git...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10d21b70580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4ec8b4e4d31ae914
dashboard link: https://syzkaller.appspot.com/bug?extid=e04e2c007ba2c80476cb
compiler:       Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6
patch:          https://syzkaller.appspot.com/x/patch.diff?x=13284f0c580000

Re: [syzbot] [hams?] KASAN: slab-use-after-free Read in rose_get_neigh

[Hillf Danton]

> Date: Mon, 21 Apr 2025 19:40:26 -0700
> syzbot has found a reproducer for the following issue on:
> 
> HEAD commit:    9d7a0577c9db gcc-15: disable '-Wunterminated-string-initia..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=139b5ccc580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=efa83f9a6dd67d67
> dashboard link: https://syzkaller.appspot.com/bug?extid=e04e2c007ba2c80476cb
> compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15652c70580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17676c70580000

#syz test upstream master

--- x/net/rose/rose_route.c
+++ y/net/rose/rose_route.c
@@ -500,8 +500,10 @@ void rose_rt_device_down(struct net_devi
 			for (i = 0; i < t->count; i++) {
 				if (t->neighbour[i] != s)
 					continue;
+				t->neighbour[i] = NULL;
 
 				t->count--;
+				continue;
 
 				switch (i) {
 				case 0:
@@ -689,6 +691,8 @@ struct rose_neigh *rose_get_neigh(rose_a
 	for (node = rose_node_list; node != NULL; node = node->next) {
 		if (rosecmpm(addr, &node->address, node->mask) == 0) {
 			for (i = 0; i < node->count; i++) {
+				if (!node->neighbour[i])
+					continue;
 				if (node->neighbour[i]->restarted) {
 					res = node->neighbour[i];
 					goto out;
@@ -700,6 +704,8 @@ struct rose_neigh *rose_get_neigh(rose_a
 		for (node = rose_node_list; node != NULL; node = node->next) {
 			if (rosecmpm(addr, &node->address, node->mask) == 0) {
 				for (i = 0; i < node->count; i++) {
+					if (!node->neighbour[i])
+						continue;
 					if (!rose_ftimer_running(node->neighbour[i])) {
 						res = node->neighbour[i];
 						goto out;
--

Re: [syzbot] [hams?] KASAN: slab-use-after-free Read in rose_get_neigh

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+e04e2c007ba2c80476cb@syzkaller.appspotmail.com
Tested-by: syzbot+e04e2c007ba2c80476cb@syzkaller.appspotmail.com

Tested on:

commit:         7595b66a Merge tag 'selinux-pr-20250624' of git://git...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14e0d182580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4ec8b4e4d31ae914
dashboard link: https://syzkaller.appspot.com/bug?extid=e04e2c007ba2c80476cb
compiler:       Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6
patch:          https://syzkaller.appspot.com/x/patch.diff?x=17775182580000

Note: testing is done by a robot and is best-effort only.

Re: [syzbot] [hams?] KASAN: slab-use-after-free Read in rose_get_neigh

[Kohei Enju]

#syz test

diff --git a/net/rose/rose_route.c b/net/rose/rose_route.c
index 2dd6bd3a3011..b72bf8a08d48 100644
--- a/net/rose/rose_route.c
+++ b/net/rose/rose_route.c
@@ -497,22 +497,15 @@ void rose_rt_device_down(struct net_device *dev)
 			t         = rose_node;
 			rose_node = rose_node->next;
 
-			for (i = 0; i < t->count; i++) {
+			for (i = t->count - 1; i >= 0; i--) {
 				if (t->neighbour[i] != s)
 					continue;
 
 				t->count--;
 
-				switch (i) {
-				case 0:
-					t->neighbour[0] = t->neighbour[1];
-					fallthrough;
-				case 1:
-					t->neighbour[1] = t->neighbour[2];
-					break;
-				case 2:
-					break;
-				}
+				memmove(&t->neighbour[i], &t->neighbour[i + 1],
+					sizeof(t->neighbour[0]) *
+						(t->count - i));
 			}
 
 			if (t->count <= 0)

Re: [syzbot] [hams?] KASAN: slab-use-after-free Read in rose_get_neigh

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+e04e2c007ba2c80476cb@syzkaller.appspotmail.com
Tested-by: syzbot+e04e2c007ba2c80476cb@syzkaller.appspotmail.com

Tested on:

commit:         aaf724ed Merge tag 'v6.16-rc3-smb3-client-fixes' of gi..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16e1c88c580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4ec8b4e4d31ae914
dashboard link: https://syzkaller.appspot.com/bug?extid=e04e2c007ba2c80476cb
compiler:       Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6
patch:          https://syzkaller.appspot.com/x/patch.diff?x=177df08c580000

Note: testing is done by a robot and is best-effort only.