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BUG: KASAN: slab-out-of-bounds in bch2_dirent_init_name+0x396/0x8b0 fs/bcachefs/dirent.c:276
Write of size 1985 at addr ffff888119814041 by task syz.2.19/6054

CPU: 1 UID: 0 PID: 6054 Comm: syz.2.19 Not tainted 6.16.0-syzkaller-11895-gcca7a0aae895-dirty #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xca/0x240 mm/kasan/report.c:482
 kasan_report+0x118/0x150 mm/kasan/report.c:595
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x2b0/0x2c0 mm/kasan/generic.c:189
 __asan_memset+0x22/0x50 mm/kasan/shadow.c:84
 bch2_dirent_init_name+0x396/0x8b0 fs/bcachefs/dirent.c:276
 bch2_dirent_create_key+0x2a1/0x5f0 fs/bcachefs/dirent.c:319
 bch2_dirent_create+0xc5/0xc80 fs/bcachefs/dirent.c:362
 bch2_link_trans+0x39e/0x560 fs/bcachefs/namei.c:241
 __bch2_link+0x231/0x3f0 fs/bcachefs/fs.c:776
 bch2_symlink+0x183/0x240 fs/bcachefs/fs.c:892
 vfs_symlink+0x143/0x2f0 fs/namei.c:4730
 do_symlinkat+0x1b1/0x3f0 fs/namei.c:4756
 __do_sys_symlinkat fs/namei.c:4772 [inline]
 __se_sys_symlinkat fs/namei.c:4769 [inline]
 __x64_sys_symlinkat+0x95/0xb0 fs/namei.c:4769
 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: 0033:0x7f8c9318ebe9
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:00007f8c93f58038 EFLAGS: 00000246 ORIG_RAX: 000000000000010a
RAX: ffffffffffffffda RBX: 00007f8c933b5fa0 RCX: 00007f8c9318ebe9
RDX: 0000200000000080 RSI: ffffffffffffff9c RDI: 0000200000000400
RBP: 00007f8c93211e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f8c933b6038 R14: 00007f8c933b5fa0 R15: 00007ffe58bc53b8
 </TASK>

Allocated by task 6054:
 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:388 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:405
 kasan_kmalloc include/linux/kasan.h:260 [inline]
 __do_kmalloc_node mm/slub.c:4365 [inline]
 __kmalloc_noprof+0x27a/0x4f0 mm/slub.c:4377
 kmalloc_noprof include/linux/slab.h:909 [inline]
 __bch2_trans_kmalloc+0x396/0x9d0 fs/bcachefs/btree_iter.c:3242
 bch2_trans_kmalloc_ip fs/bcachefs/btree_iter.h:604 [inline]
 bch2_trans_kmalloc fs/bcachefs/btree_iter.h:616 [inline]
 bch2_dirent_create_key+0x113/0x5f0 fs/bcachefs/dirent.c:302
 bch2_dirent_create+0xc5/0xc80 fs/bcachefs/dirent.c:362
 bch2_link_trans+0x39e/0x560 fs/bcachefs/namei.c:241
 __bch2_link+0x231/0x3f0 fs/bcachefs/fs.c:776
 bch2_symlink+0x183/0x240 fs/bcachefs/fs.c:892
 vfs_symlink+0x143/0x2f0 fs/namei.c:4730
 do_symlinkat+0x1b1/0x3f0 fs/namei.c:4756
 __do_sys_symlinkat fs/namei.c:4772 [inline]
 __se_sys_symlinkat fs/namei.c:4769 [inline]
 __x64_sys_symlinkat+0x95/0xb0 fs/namei.c:4769
 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 ffff888119814000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 65 bytes inside of
 allocated 2048-byte region [ffff888119814000, ffff888119814800)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x119810
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x57ff00000000040(head|node=1|zone=2|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 057ff00000000040 ffff88801a442000 dead000000000100 dead000000000122
raw: 0000000000000000 0000000080080008 00000000f5000000 0000000000000000
head: 057ff00000000040 ffff88801a442000 dead000000000100 dead000000000122
head: 0000000000000000 0000000080080008 00000000f5000000 0000000000000000
head: 057ff00000000003 ffffea0004660401 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5905, tgid 5905 (syz-executor), ts 58666949691, free_ts 0
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x240/0x2a0 mm/page_alloc.c:1851
 prep_new_page mm/page_alloc.c:1859 [inline]
 get_page_from_freelist+0x21e4/0x22c0 mm/page_alloc.c:3858
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5148
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2416
 alloc_slab_page mm/slub.c:2487 [inline]
 allocate_slab+0x8a/0x370 mm/slub.c:2655
 new_slab mm/slub.c:2709 [inline]
 ___slab_alloc+0xbeb/0x1410 mm/slub.c:3891
 __slab_alloc mm/slub.c:3981 [inline]
 __slab_alloc_node mm/slub.c:4056 [inline]
 slab_alloc_node mm/slub.c:4217 [inline]
 __do_kmalloc_node mm/slub.c:4364 [inline]
 __kmalloc_noprof+0x305/0x4f0 mm/slub.c:4377
 kmalloc_noprof include/linux/slab.h:909 [inline]
 kmalloc_array_noprof include/linux/slab.h:948 [inline]
 cache_create_net+0x92/0x260 net/sunrpc/cache.c:1747
 nfsd_idmap_init+0x59/0x1f0 fs/nfsd/nfs4idmap.c:470
 nfsd_net_init+0x4d/0x480 fs/nfsd/nfsctl.c:2190
 ops_init+0x35c/0x5c0 net/core/net_namespace.c:136
 setup_net+0x10c/0x320 net/core/net_namespace.c:438
 copy_net_ns+0x31b/0x4d0 net/core/net_namespace.c:570
 create_new_namespaces+0x3f3/0x720 kernel/nsproxy.c:110
 unshare_nsproxy_namespaces+0x11c/0x170 kernel/nsproxy.c:218
 ksys_unshare+0x4c8/0x8c0 kernel/fork.c:3127
page_owner free stack trace missing

Memory state around the buggy address:
 ffff888119814700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888119814780: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888119814800: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                   ^
 ffff888119814880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888119814900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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