syzbot

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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+0x2583/0x29b0 net/netrom/nr_route.c:692
Read of size 4 at addr ffff888029989db0 by task syz.1.252/6389

CPU: 0 UID: 0 PID: 6389 Comm: syz.1.252 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
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:378 [inline]
 print_report+0xcd/0x630 mm/kasan/report.c:482
 kasan_report+0xe0/0x110 mm/kasan/report.c:595
 nr_dec_obs net/netrom/nr_route.c:471 [inline]
 nr_rt_ioctl+0x2583/0x29b0 net/netrom/nr_route.c:692
 nr_ioctl+0x19a/0x2d0 net/netrom/af_netrom.c:1254
 sock_do_ioctl+0x118/0x280 net/socket.c:1254
 sock_ioctl+0x227/0x6b0 net/socket.c:1375
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl fs/ioctl.c:583 [inline]
 __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f5ee5f8efc9
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:00007ffef25fa018 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f5ee61e5fa0 RCX: 00007f5ee5f8efc9
RDX: 0000000000000000 RSI: 00000000000089e2 RDI: 0000000000000004
RBP: 00007f5ee6011f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f5ee61e5fa0 R14: 00007f5ee61e5fa0 R15: 0000000000000002
 </TASK>

Allocated by task 6390:
 kasan_save_stack+0x33/0x60 mm/kasan/common.c:56
 kasan_save_track+0x14/0x30 mm/kasan/common.c:77
 poison_kmalloc_redzone mm/kasan/common.c:400 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:417
 kmalloc_noprof include/linux/slab.h:957 [inline]
 nr_add_node+0xe4e/0x2c00 net/netrom/nr_route.c:146
 nr_rt_ioctl+0x11b7/0x29b0 net/netrom/nr_route.c:651
 nr_ioctl+0x19a/0x2d0 net/netrom/af_netrom.c:1254
 sock_do_ioctl+0x118/0x280 net/socket.c:1254
 sock_ioctl+0x227/0x6b0 net/socket.c:1375
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl fs/ioctl.c:583 [inline]
 __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 6389:
 kasan_save_stack+0x33/0x60 mm/kasan/common.c:56
 kasan_save_track+0x14/0x30 mm/kasan/common.c:77
 __kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:587
 kasan_save_free_info mm/kasan/kasan.h:406 [inline]
 poison_slab_object mm/kasan/common.c:252 [inline]
 __kasan_slab_free+0x5f/0x80 mm/kasan/common.c:284
 kasan_slab_free include/linux/kasan.h:234 [inline]
 slab_free_hook mm/slub.c:2530 [inline]
 slab_free mm/slub.c:6619 [inline]
 kfree+0x2b8/0x6d0 mm/slub.c:6826
 nr_neigh_put include/net/netrom.h:143 [inline]
 nr_neigh_put include/net/netrom.h:137 [inline]
 nr_dec_obs net/netrom/nr_route.c:469 [inline]
 nr_rt_ioctl+0xbed/0x29b0 net/netrom/nr_route.c:692
 nr_ioctl+0x19a/0x2d0 net/netrom/af_netrom.c:1254
 sock_do_ioctl+0x118/0x280 net/socket.c:1254
 sock_ioctl+0x227/0x6b0 net/socket.c:1375
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl fs/ioctl.c:583 [inline]
 __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888029989d80
 which belongs to the cache kmalloc-64 of size 64
The buggy address is located 48 bytes inside of
 freed 64-byte region [ffff888029989d80, ffff888029989dc0)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x29989
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000000 ffff88801b4428c0 ffffea0000b5be80 dead000000000002
raw: 0000000000000000 0000000080200020 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 0x52c40(GFP_NOFS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 5950, tgid 5950 (syz-executor), ts 56857784362, free_ts 56857046348
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1c0/0x230 mm/page_alloc.c:1850
 prep_new_page mm/page_alloc.c:1858 [inline]
 get_page_from_freelist+0x10a3/0x3a30 mm/page_alloc.c:3884
 __alloc_frozen_pages_noprof+0x25f/0x2470 mm/page_alloc.c:5183
 alloc_pages_mpol+0x1fb/0x550 mm/mempolicy.c:2416
 alloc_slab_page mm/slub.c:3046 [inline]
 allocate_slab mm/slub.c:3219 [inline]
 new_slab+0x24a/0x360 mm/slub.c:3273
 ___slab_alloc+0xdc4/0x1ae0 mm/slub.c:4643
 __slab_alloc.constprop.0+0x63/0x110 mm/slub.c:4762
 __slab_alloc_node mm/slub.c:4838 [inline]
 slab_alloc_node mm/slub.c:5260 [inline]
 __do_kmalloc_node mm/slub.c:5633 [inline]
 __kmalloc_noprof+0x501/0x880 mm/slub.c:5646
 kmalloc_noprof include/linux/slab.h:961 [inline]
 kzalloc_noprof include/linux/slab.h:1094 [inline]
 tomoyo_encode2+0x100/0x3e0 security/tomoyo/realpath.c:45
 tomoyo_encode+0x29/0x50 security/tomoyo/realpath.c:80
 tomoyo_realpath_from_path+0x18f/0x6e0 security/tomoyo/realpath.c:283
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_path_number_perm+0x245/0x580 security/tomoyo/file.c:723
 tomoyo_path_mkdir+0x9b/0xe0 security/tomoyo/tomoyo.c:179
 security_path_mkdir+0x154/0x2f0 security/security.c:1971
 do_mkdirat+0x175/0x3e0 fs/namei.c:4483
 __do_sys_mkdirat fs/namei.c:4503 [inline]
 __se_sys_mkdirat fs/namei.c:4501 [inline]
 __x64_sys_mkdirat+0x83/0xb0 fs/namei.c:4501
page last free pid 5950 tgid 5950 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1394 [inline]
 __free_frozen_pages+0x7df/0x1160 mm/page_alloc.c:2906
 selinux_genfs_get_sid security/selinux/hooks.c:1357 [inline]
 inode_doinit_with_dentry+0xacb/0x12e0 security/selinux/hooks.c:1555
 selinux_d_instantiate+0x26/0x30 security/selinux/hooks.c:6523
 security_d_instantiate+0x142/0x1a0 security/security.c:4148
 d_splice_alias_ops+0x92/0x840 fs/dcache.c:3001
 proc_sys_lookup+0x285/0x400 fs/proc/proc_sysctl.c:544
 __lookup_slow+0x251/0x460 fs/namei.c:1816
 lookup_slow fs/namei.c:1833 [inline]
 walk_component+0x353/0x5b0 fs/namei.c:2151
 lookup_last fs/namei.c:2652 [inline]
 path_lookupat+0x142/0x6d0 fs/namei.c:2676
 filename_lookup+0x224/0x5f0 fs/namei.c:2705
 user_path_at+0x3a/0x60 fs/namei.c:3215
 do_mount fs/namespace.c:4047 [inline]
 __do_sys_mount fs/namespace.c:4238 [inline]
 __se_sys_mount fs/namespace.c:4215 [inline]
 __x64_sys_mount+0x1fb/0x310 fs/namespace.c:4215
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff888029989c80: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
 ffff888029989d00: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>ffff888029989d80: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
                                     ^
 ffff888029989e00: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
 ffff888029989e80: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
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