syzbot

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BUG: KASAN: slab-use-after-free in p9_fcall_init+0x1a9/0x1e0 net/9p/client.c:229
Read of size 8 at addr ffff888046d9ac60 by task kworker/u32:0/11

CPU: 3 PID: 11 Comm: kworker/u32:0 Not tainted 6.9.0-syzkaller-08284-gea5f6ad9ad96 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Workqueue: events_unbound netfs_write_collection_worker
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:114
 print_address_description mm/kasan/report.c:377 [inline]
 print_report+0xc3/0x620 mm/kasan/report.c:488
 kasan_report+0xd9/0x110 mm/kasan/report.c:601
 p9_fcall_init+0x1a9/0x1e0 net/9p/client.c:229
 p9_tag_alloc+0x21c/0x870 net/9p/client.c:298
 p9_client_prepare_req+0x19f/0x4d0 net/9p/client.c:642
 p9_client_rpc+0x1c3/0xc10 net/9p/client.c:689
 p9_client_clunk+0x93/0x170 net/9p/client.c:1439
 p9_fid_put include/net/9p/client.h:280 [inline]
 v9fs_free_request+0xdc/0x110 fs/9p/vfs_addr.c:138
 netfs_free_request+0x22c/0x690 fs/netfs/objects.c:133
 netfs_put_request+0x19b/0x1f0 fs/netfs/objects.c:165
 netfs_write_collection_worker+0x19d0/0x59e0 fs/netfs/write_collect.c:701
 process_one_work+0x9fb/0x1b60 kernel/workqueue.c:3231
 process_scheduled_works kernel/workqueue.c:3312 [inline]
 worker_thread+0x6c8/0xf70 kernel/workqueue.c:3393
 kthread+0x2c1/0x3a0 kernel/kthread.c:389
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>

Allocated by task 7329:
 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:370 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:387
 kmalloc include/linux/slab.h:628 [inline]
 p9_client_create+0xcf/0x1210 net/9p/client.c:981
 v9fs_session_init+0x1f8/0x1a80 fs/9p/v9fs.c:410
 v9fs_mount+0xc6/0xaa0 fs/9p/vfs_super.c:122
 legacy_get_tree+0x109/0x220 fs/fs_context.c:662
 vfs_get_tree+0x8f/0x380 fs/super.c:1779
 do_new_mount fs/namespace.c:3352 [inline]
 path_mount+0x14e6/0x1f20 fs/namespace.c:3679
 do_mount fs/namespace.c:3692 [inline]
 __do_sys_mount fs/namespace.c:3898 [inline]
 __se_sys_mount fs/namespace.c:3875 [inline]
 __x64_sys_mount+0x297/0x320 fs/namespace.c:3875
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcf/0x260 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 6787:
 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:579
 poison_slab_object mm/kasan/common.c:240 [inline]
 __kasan_slab_free+0x11d/0x1a0 mm/kasan/common.c:256
 kasan_slab_free include/linux/kasan.h:184 [inline]
 slab_free_hook mm/slub.c:2121 [inline]
 slab_free mm/slub.c:4353 [inline]
 kfree+0x129/0x3a0 mm/slub.c:4463
 p9_client_destroy+0x2e6/0x480 net/9p/client.c:1077
 v9fs_session_close+0x49/0x2d0 fs/9p/v9fs.c:506
 v9fs_kill_super+0x4d/0xa0 fs/9p/vfs_super.c:196
 deactivate_locked_super+0xbe/0x1a0 fs/super.c:472
 deactivate_super+0xde/0x100 fs/super.c:505
 cleanup_mnt+0x222/0x450 fs/namespace.c:1267
 task_work_run+0x14e/0x250 kernel/task_work.c:180
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:114 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0x278/0x2a0 kernel/entry/common.c:218
 do_syscall_64+0xdc/0x260 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888046d9ac00
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 96 bytes inside of
 freed 512-byte region [ffff888046d9ac00, ffff888046d9ae00)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x46d98
head: order:2 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000840(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000840 ffff888015442c80 ffffea0000ab5c00 dead000000000002
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
head: 00fff00000000840 ffff888015442c80 ffffea0000ab5c00 dead000000000002
head: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
head: 00fff00000000002 ffffea00011b6601 ffffea00011b6648 00000000ffffffff
head: 0000000400000000 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 5227, tgid 5227 (syz-executor.1), ts 67339507214, free_ts 0
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x2d4/0x350 mm/page_alloc.c:1534
 prep_new_page mm/page_alloc.c:1541 [inline]
 get_page_from_freelist+0xa28/0x3780 mm/page_alloc.c:3317
 __alloc_pages+0x22b/0x2460 mm/page_alloc.c:4575
 __alloc_pages_node include/linux/gfp.h:238 [inline]
 alloc_pages_node include/linux/gfp.h:261 [inline]
 alloc_slab_page mm/slub.c:2190 [inline]
 allocate_slab mm/slub.c:2353 [inline]
 new_slab+0xcc/0x3a0 mm/slub.c:2406
 ___slab_alloc+0xd28/0x1810 mm/slub.c:3592
 __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3682
 __slab_alloc_node mm/slub.c:3735 [inline]
 slab_alloc_node mm/slub.c:3908 [inline]
 __do_kmalloc_node mm/slub.c:4038 [inline]
 __kmalloc+0x3bf/0x440 mm/slub.c:4052
 kmalloc include/linux/slab.h:632 [inline]
 kzalloc include/linux/slab.h:749 [inline]
 new_dir fs/proc/proc_sysctl.c:956 [inline]
 get_subdir fs/proc/proc_sysctl.c:1000 [inline]
 sysctl_mkdir_p fs/proc/proc_sysctl.c:1295 [inline]
 __register_sysctl_table+0xdab/0x16c0 fs/proc/proc_sysctl.c:1376
 neigh_sysctl_register+0x31a/0x640 net/core/neighbour.c:3861
 addrconf_sysctl_register+0xb9/0x1f0 net/ipv6/addrconf.c:7259
 ipv6_add_dev+0x9d5/0x1400 net/ipv6/addrconf.c:456
 addrconf_notify+0x546/0x19e0 net/ipv6/addrconf.c:3652
 notifier_call_chain+0xb9/0x410 kernel/notifier.c:93
 call_netdevice_notifiers_info+0xbe/0x140 net/core/dev.c:1992
 call_netdevice_notifiers_extack net/core/dev.c:2030 [inline]
 call_netdevice_notifiers net/core/dev.c:2044 [inline]
 register_netdevice+0x15f5/0x1ca0 net/core/dev.c:10407
 veth_newlink+0x363/0xa10 drivers/net/veth.c:1829
page_owner free stack trace missing

Memory state around the buggy address:
 ffff888046d9ab00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888046d9ab80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888046d9ac00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                       ^
 ffff888046d9ac80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888046d9ad00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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