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BUG: KASAN: slab-out-of-bounds in bch2_dirent_init_name+0x300/0x724 fs/bcachefs/dirent.c:276
Write of size 1985 at addr ffff0000f5989041 by task syz.2.65/7010

CPU: 0 UID: 0 PID: 7010 Comm: syz.2.65 Not tainted syzkaller #0 PREEMPT 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/30/2025
Call trace:
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:499 (C)
 __dump_stack+0x30/0x40 lib/dump_stack.c:94
 dump_stack_lvl+0xd8/0x12c lib/dump_stack.c:120
 print_address_description+0xa8/0x238 mm/kasan/report.c:378
 print_report+0x68/0x84 mm/kasan/report.c:482
 kasan_report+0xb0/0x110 mm/kasan/report.c:595
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x264/0x2a4 mm/kasan/generic.c:189
 __asan_memset+0x34/0x64 mm/kasan/shadow.c:84
 bch2_dirent_init_name+0x300/0x724 fs/bcachefs/dirent.c:276
 bch2_dirent_create_key+0x1a0/0x424 fs/bcachefs/dirent.c:319
 bch2_dirent_create+0xec/0x9fc fs/bcachefs/dirent.c:362
 bch2_link_trans+0x310/0x474 fs/bcachefs/namei.c:241
 __bch2_link+0x1b0/0x350 fs/bcachefs/fs.c:776
 bch2_symlink+0x140/0x1cc fs/bcachefs/fs.c:892
 vfs_symlink+0x138/0x288 fs/namei.c:4730
 do_symlinkat+0x17c/0x360 fs/namei.c:4756
 __do_sys_symlinkat fs/namei.c:4772 [inline]
 __se_sys_symlinkat fs/namei.c:4769 [inline]
 __arm64_sys_symlinkat+0x9c/0xb4 fs/namei.c:4769
 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
 invoke_syscall+0x98/0x254 arch/arm64/kernel/syscall.c:49
 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
 el0_svc+0x5c/0x254 arch/arm64/kernel/entry-common.c:744
 el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:763
 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596

Allocated by task 7010:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x40/0x78 mm/kasan/common.c:68
 kasan_save_alloc_info+0x44/0x54 mm/kasan/generic.c:562
 poison_kmalloc_redzone mm/kasan/common.c:388 [inline]
 __kasan_kmalloc+0x9c/0xb4 mm/kasan/common.c:405
 kasan_kmalloc include/linux/kasan.h:260 [inline]
 __do_kmalloc_node mm/slub.c:4376 [inline]
 __kmalloc_noprof+0x2fc/0x4c8 mm/slub.c:4388
 kmalloc_noprof include/linux/slab.h:909 [inline]
 __bch2_trans_kmalloc+0x38c/0x96c fs/bcachefs/btree_iter.c:3242
 bch2_trans_kmalloc_ip fs/bcachefs/btree_iter.h:604 [inline]
 bch2_trans_kmalloc+0x10c/0x160 fs/bcachefs/btree_iter.h:616
 bch2_dirent_create_key+0x50/0x424 fs/bcachefs/dirent.c:302
 bch2_dirent_create+0xec/0x9fc fs/bcachefs/dirent.c:362
 bch2_link_trans+0x310/0x474 fs/bcachefs/namei.c:241
 __bch2_link+0x1b0/0x350 fs/bcachefs/fs.c:776
 bch2_symlink+0x140/0x1cc fs/bcachefs/fs.c:892
 vfs_symlink+0x138/0x288 fs/namei.c:4730
 do_symlinkat+0x17c/0x360 fs/namei.c:4756
 __do_sys_symlinkat fs/namei.c:4772 [inline]
 __se_sys_symlinkat fs/namei.c:4769 [inline]
 __arm64_sys_symlinkat+0x9c/0xb4 fs/namei.c:4769
 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
 invoke_syscall+0x98/0x254 arch/arm64/kernel/syscall.c:49
 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
 el0_svc+0x5c/0x254 arch/arm64/kernel/entry-common.c:744
 el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:763
 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596

The buggy address belongs to the object at ffff0000f5989000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 65 bytes inside of
 allocated 2048-byte region [ffff0000f5989000, ffff0000f5989800)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x135988
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
anon flags: 0x5ffc00000000040(head|node=0|zone=2|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 05ffc00000000040 ffff0000c0002000 0000000000000000 dead000000000001
raw: 0000000000000000 0000000080080008 00000000f5000000 0000000000000000
head: 05ffc00000000040 ffff0000c0002000 0000000000000000 dead000000000001
head: 0000000000000000 0000000080080008 00000000f5000000 0000000000000000
head: 05ffc00000000003 fffffdffc3d66201 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff0000f5989700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff0000f5989780: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff0000f5989800: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                   ^
 ffff0000f5989880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff0000f5989900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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