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BUG: KASAN: slab-use-after-free in generic_test_bit include/asm-generic/bitops/generic-non-atomic.h:128 [inline]
BUG: KASAN: slab-use-after-free in bch2_bucket_bitmap_test fs/bcachefs/backpointers.h:194 [inline]
BUG: KASAN: slab-use-after-free in bch2_bucket_is_movable fs/bcachefs/movinggc.c:78 [inline]
BUG: KASAN: slab-use-after-free in bch2_copygc_get_buckets fs/bcachefs/movinggc.c:157 [inline]
BUG: KASAN: slab-use-after-free in bch2_copygc+0xb34/0x3570 fs/bcachefs/movinggc.c:221
Read of size 8 at addr ffff0000d0783800 by task bch-copygc/loop/8972

CPU: 1 UID: 0 PID: 8972 Comm: bch-copygc/loop Not tainted 6.17.0-rc1-syzkaller-g8f5ae30d69d7 #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
 __asan_report_load8_noabort+0x20/0x2c mm/kasan/report_generic.c:381
 generic_test_bit include/asm-generic/bitops/generic-non-atomic.h:128 [inline]
 bch2_bucket_bitmap_test fs/bcachefs/backpointers.h:194 [inline]
 bch2_bucket_is_movable fs/bcachefs/movinggc.c:78 [inline]
 bch2_copygc_get_buckets fs/bcachefs/movinggc.c:157 [inline]
 bch2_copygc+0xb34/0x3570 fs/bcachefs/movinggc.c:221
 bch2_copygc_thread+0x898/0xd8c fs/bcachefs/movinggc.c:409
 kthread+0x5fc/0x75c kernel/kthread.c:463
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:844

Allocated by task 8972:
 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:4365 [inline]
 __kvmalloc_node_noprof+0x38c/0x638 mm/slub.c:5052
 kvmalloc_array_node_noprof include/linux/slab.h:1065 [inline]
 bch2_bucket_bitmap_set+0x160/0x1bc fs/bcachefs/backpointers.c:1351
 check_bucket_backpointer_mismatch+0x1288/0x1860 fs/bcachefs/backpointers.c:964
 check_bucket_backpointer_pos_mismatch fs/bcachefs/backpointers.c:1193 [inline]
 bch2_check_bucket_backpointer_mismatch+0x16c/0x3a0 fs/bcachefs/backpointers.c:1205
 __bch2_move_data_phys+0x1144/0x144c fs/bcachefs/move.c:922
 bch2_evacuate_bucket+0x220/0x34c fs/bcachefs/move.c:1082
 bch2_copygc+0x2d80/0x3570 fs/bcachefs/movinggc.c:234
 bch2_copygc_thread+0x898/0xd8c fs/bcachefs/movinggc.c:409
 kthread+0x5fc/0x75c kernel/kthread.c:463
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:844

The buggy address belongs to the object at ffff0000d0783800
 which belongs to the cache kmalloc-16 of size 16
The buggy address is located 0 bytes inside of
 freed 16-byte region [ffff0000d0783800, ffff0000d0783810)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x110783
flags: 0x5ffc00000000000(node=0|zone=2|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 05ffc00000000000 ffff0000c0001640 dead000000000100 dead000000000122
raw: 0000000000000000 0000000080800080 00000000f5000000 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff0000d0783700: fa fb fc fc fa fb fc fc fa fb fc fc fa fb fc fc
 ffff0000d0783780: fa fb fc fc fa fb fc fc fa fb fc fc fa fb fc fc
>ffff0000d0783800: fb fb fc fc fa fb fc fc fa fb fc fc fa fb fc fc
                   ^
 ffff0000d0783880: fa fb fc fc fa fb fc fc fa fb fc fc fa fb fc fc
 ffff0000d0783900: fa fb fc fc fa fb fc fc 00 00 fc fc fa fb fc fc
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