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BUG: KASAN: slab-out-of-bounds in __cache_seq_start net/sunrpc/cache.c:1351 [inline]
BUG: KASAN: slab-out-of-bounds in cache_seq_start_rcu+0x3fe/0x420 net/sunrpc/cache.c:1399
Read of size 8 at addr ffff888031554800 by task syz.4.475/8220

CPU: 0 UID: 0 PID: 8220 Comm: syz.4.475 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0x13d/0x4b0 mm/kasan/report.c:482
 kasan_report+0xdf/0x1d0 mm/kasan/report.c:595
 __cache_seq_start net/sunrpc/cache.c:1351 [inline]
 cache_seq_start_rcu+0x3fe/0x420 net/sunrpc/cache.c:1399
 seq_read_iter+0x2c1/0x1270 fs/seq_file.c:226
 seq_read+0x33b/0x4c0 fs/seq_file.c:163
 pde_read fs/proc/inode.c:308 [inline]
 proc_reg_read+0x240/0x330 fs/proc/inode.c:320
 vfs_read+0x1e4/0xb30 fs/read_write.c:572
 ksys_pread64 fs/read_write.c:765 [inline]
 __do_sys_pread64 fs/read_write.c:773 [inline]
 __se_sys_pread64 fs/read_write.c:770 [inline]
 __x64_sys_pread64+0x1eb/0x250 fs/read_write.c:770
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x10b/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f1079f9cdd9
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:00007f107af1e028 EFLAGS: 00000246 ORIG_RAX: 0000000000000011
RAX: ffffffffffffffda RBX: 00007f107a215fa0 RCX: 00007f1079f9cdd9
RDX: 00000000000001ff RSI: 0000000000000000 RDI: 0000000000000006
RBP: 00007f107a032d69 R08: 0000000000000000 R09: 0000000000000000
R10: 0000008800000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f107a216038 R14: 00007f107a215fa0 R15: 00007ffcd398b578
 </TASK>

Allocated by task 6736:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:415
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __do_kmalloc_node mm/slub.c:5295 [inline]
 __kmalloc_noprof+0x301/0x850 mm/slub.c:5307
 kmalloc_noprof include/linux/slab.h:954 [inline]
 kzalloc_noprof include/linux/slab.h:1188 [inline]
 cache_create_net+0xa2/0x1f0 net/sunrpc/cache.c:1733
 nfsd_export_init+0x62/0x250 fs/nfsd/export.c:1536
 nfsd_net_init+0x69/0x3e0 fs/nfsd/nfsctl.c:2209
 ops_init+0x1e2/0x5f0 net/core/net_namespace.c:137
 setup_net+0x118/0x3a0 net/core/net_namespace.c:446
 copy_net_ns+0x46f/0x7c0 net/core/net_namespace.c:579
 create_new_namespaces+0x3ea/0xac0 kernel/nsproxy.c:132
 unshare_nsproxy_namespaces+0xf2/0x220 kernel/nsproxy.c:234
 ksys_unshare+0x438/0xab0 kernel/fork.c:3245
 __do_sys_unshare kernel/fork.c:3319 [inline]
 __se_sys_unshare kernel/fork.c:3317 [inline]
 __x64_sys_unshare+0x31/0x40 kernel/fork.c:3317
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x10b/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888031554000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 0 bytes to the right of
 allocated 2048-byte region [ffff888031554000, ffff888031554800)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x31550
head: order:3 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 ffff88813fe2e000 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800080008 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88813fe2e000 dead000000000100 dead000000000122
head: 0000000000000000 0000000800080008 00000000f5000000 0000000000000000
head: 00fff00000000003 fffffffffffffe01 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd28c0(GFP_NOWAIT|__GFP_IO|__GFP_FS|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5627, tgid 5627 (syz-executor), ts 97815725294, free_ts 71826744058
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x153/0x170 mm/page_alloc.c:1858
 prep_new_page mm/page_alloc.c:1866 [inline]
 get_page_from_freelist+0x11a6/0x33b0 mm/page_alloc.c:3946
 __alloc_frozen_pages_noprof+0x27c/0x2bc0 mm/page_alloc.c:5226
 alloc_slab_page mm/slub.c:3278 [inline]
 allocate_slab mm/slub.c:3467 [inline]
 new_slab+0xa6/0x6c0 mm/slub.c:3525
 refill_objects+0x277/0x420 mm/slub.c:7251
 refill_sheaf mm/slub.c:2816 [inline]
 __pcs_replace_empty_main+0x375/0x650 mm/slub.c:4651
 alloc_from_pcs mm/slub.c:4749 [inline]
 slab_alloc_node mm/slub.c:4883 [inline]
 __do_kmalloc_node mm/slub.c:5294 [inline]
 __kmalloc_node_track_caller_noprof+0x694/0x850 mm/slub.c:5403
 kmalloc_reserve+0xe8/0x350 net/core/skbuff.c:635
 pskb_expand_head+0x249/0x10e0 net/core/skbuff.c:2302
 netlink_trim+0x22d/0x2f0 net/netlink/af_netlink.c:1299
 netlink_broadcast_filtered+0x69/0xe90 net/netlink/af_netlink.c:1512
 nlmsg_multicast_filtered include/net/netlink.h:1165 [inline]
 nlmsg_multicast include/net/netlink.h:1184 [inline]
 nlmsg_notify+0xb1/0x290 net/netlink/af_netlink.c:2593
 rtnl_notify net/core/rtnetlink.c:964 [inline]
 rtmsg_ifinfo_send net/core/rtnetlink.c:4473 [inline]
 rtmsg_ifinfo_event net/core/rtnetlink.c:4489 [inline]
 rtmsg_ifinfo_event net/core/rtnetlink.c:4476 [inline]
 rtmsg_ifinfo+0x177/0x1b0 net/core/rtnetlink.c:4495
 register_netdevice+0x1d9c/0x24b0 net/core/dev.c:11472
 nsim_init_netdevsim drivers/net/netdevsim/netdev.c:1069 [inline]
 nsim_create+0xc8d/0x1420 drivers/net/netdevsim/netdev.c:1151
 __nsim_dev_port_add+0x3ba/0x8f0 drivers/net/netdevsim/dev.c:1509
page last free pid 5446 tgid 5446 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1402 [inline]
 __free_frozen_pages+0x747/0x1040 mm/page_alloc.c:2943
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x47/0xf0 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x1a0/0x1f0 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x69/0x90 mm/kasan/common.c:350
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4569 [inline]
 slab_alloc_node mm/slub.c:4898 [inline]
 __do_kmalloc_node mm/slub.c:5294 [inline]
 __kmalloc_noprof+0x2b9/0x850 mm/slub.c:5307
 kmalloc_noprof include/linux/slab.h:954 [inline]
 tomoyo_realpath_from_path+0xb6/0x690 security/tomoyo/realpath.c:251
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_path_perm+0x276/0x460 security/tomoyo/file.c:827
 security_file_truncate+0xb5/0x1e0 security/security.c:2771
 handle_truncate fs/namei.c:4305 [inline]
 do_open fs/namei.c:4703 [inline]
 path_openat+0x1c6e/0x31a0 fs/namei.c:4858
 do_file_open+0x20e/0x430 fs/namei.c:4887
 do_sys_openat2+0x10d/0x1e0 fs/open.c:1364
 do_sys_open fs/open.c:1370 [inline]
 __do_sys_openat fs/open.c:1386 [inline]
 __se_sys_openat fs/open.c:1381 [inline]
 __x64_sys_openat+0x12d/0x210 fs/open.c:1381
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x10b/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff888031554700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888031554780: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888031554800: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                   ^
 ffff888031554880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888031554900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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