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BUG: KASAN: slab-use-after-free in nr_dec_obs net/netrom/nr_route.c:471 [inline]
BUG: KASAN: slab-use-after-free in nr_rt_ioctl+0x610/0xf90 net/netrom/nr_route.c:692
Read of size 2 at addr ffff888033816832 by task syz.3.353/7280

CPU: 1 UID: 0 PID: 7280 Comm: syz.3.353 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xba/0x230 mm/kasan/report.c:482
 kasan_report+0x117/0x150 mm/kasan/report.c:595
 nr_dec_obs net/netrom/nr_route.c:471 [inline]
 nr_rt_ioctl+0x610/0xf90 net/netrom/nr_route.c:692
 sock_do_ioctl+0x101/0x320 net/socket.c:1254
 sock_ioctl+0x5c6/0x7f0 net/socket.c:1375
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fe6c819ae79
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fe6c8f7f028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fe6c8405fa0 RCX: 00007fe6c819ae79
RDX: 0000000000000000 RSI: 00000000000089e2 RDI: 0000000000000007
RBP: 00007fe6c822dee0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fe6c8406038 R14: 00007fe6c8405fa0 R15: 00007ffd0ccaeb58
 </TASK>

Allocated by task 7280:
 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]
 __kmalloc_cache_noprof+0x31c/0x660 mm/slub.c:5297
 kmalloc_noprof include/linux/slab.h:962 [inline]
 nr_add_node+0x25b/0x2630 net/netrom/nr_route.c:146
 nr_rt_ioctl+0xe59/0xf90 net/netrom/nr_route.c:651
 sock_do_ioctl+0x101/0x320 net/socket.c:1254
 sock_ioctl+0x5c6/0x7f0 net/socket.c:1375
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 7280:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 kasan_save_free_info+0x46/0x50 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:2670 [inline]
 slab_free mm/slub.c:6082 [inline]
 kfree+0x1c1/0x610 mm/slub.c:6399
 nr_dec_obs net/netrom/nr_route.c:469 [inline]
 nr_rt_ioctl+0x363/0xf90 net/netrom/nr_route.c:692
 sock_do_ioctl+0x101/0x320 net/socket.c:1254
 sock_ioctl+0x5c6/0x7f0 net/socket.c:1375
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888033816800
 which belongs to the cache kmalloc-64 of size 64
The buggy address is located 50 bytes inside of
 freed 64-byte region [ffff888033816800, ffff888033816840)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x33816
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000000 ffff88813fe9a8c0 dead000000000100 dead000000000122
raw: 0000000000000000 0000000000200020 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 0xd2c40(GFP_NOFS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5192, tgid 5192 (udevd), ts 40995415811, free_ts 40980675376
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x228/0x280 mm/page_alloc.c:1884
 prep_new_page mm/page_alloc.c:1892 [inline]
 get_page_from_freelist+0x24dc/0x2580 mm/page_alloc.c:3950
 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5245
 alloc_slab_page mm/slub.c:3238 [inline]
 allocate_slab+0x77/0x660 mm/slub.c:3411
 new_slab mm/slub.c:3469 [inline]
 refill_objects+0x331/0x3c0 mm/slub.c:7091
 refill_sheaf mm/slub.c:2787 [inline]
 __pcs_replace_empty_main+0x2b9/0x620 mm/slub.c:4536
 alloc_from_pcs mm/slub.c:4639 [inline]
 slab_alloc_node mm/slub.c:4773 [inline]
 __do_kmalloc_node mm/slub.c:5176 [inline]
 __kmalloc_noprof+0x474/0x760 mm/slub.c:5189
 kmalloc_noprof include/linux/slab.h:966 [inline]
 kzalloc_noprof include/linux/slab.h:1204 [inline]
 tomoyo_encode2 security/tomoyo/realpath.c:45 [inline]
 tomoyo_encode+0x28b/0x550 security/tomoyo/realpath.c:80
 tomoyo_realpath_from_path+0x58d/0x5d0 security/tomoyo/realpath.c:283
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_check_open_permission+0x229/0x470 security/tomoyo/file.c:776
 security_file_open+0xa9/0x240 security/security.c:2636
 do_dentry_open+0x384/0x14e0 fs/open.c:926
 vfs_open+0x3b/0x340 fs/open.c:1081
 do_open fs/namei.c:4671 [inline]
 path_openat+0x2e08/0x3860 fs/namei.c:4830
 do_file_open+0x23e/0x4a0 fs/namei.c:4859
 do_sys_openat2+0x113/0x200 fs/open.c:1366
page last free pid 5202 tgid 5202 stack trace:
 create_dummy_stack mm/page_owner.c:103 [inline]
 register_dummy_stack+0x98/0x100 mm/page_owner.c:109
 init_page_owner+0x2e/0x600 mm/page_owner.c:127
 invoke_init_callbacks mm/page_ext.c:152 [inline]
 page_ext_init+0x500/0x540 mm/page_ext.c:490
 mm_core_init+0x56/0x70 mm/mm_init.c:2729

Memory state around the buggy address:
 ffff888033816700: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
 ffff888033816780: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
>ffff888033816800: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
                                     ^
 ffff888033816880: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
 ffff888033816900: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
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