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BUG: KASAN: slab-out-of-bounds in bch2_sb_downgrade_to_text+0x58d/0x680 fs/bcachefs/sb-downgrade.c:185
Read of size 2 at addr ffff888041d52000 by task syz-executor.2/10315

CPU: 0 PID: 10315 Comm: syz-executor.2 Not tainted 6.9.0-rc6-syzkaller-00290-gb9158815de52 #0
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 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
 bch2_sb_downgrade_to_text+0x58d/0x680 fs/bcachefs/sb-downgrade.c:185
 __bch2_sb_field_to_text+0x123/0x1e0 fs/bcachefs/super-io.c:1228
 bch2_sb_field_validate+0x248/0x2d0 fs/bcachefs/super-io.c:1211
 bch2_sb_validate.isra.0+0x6d8/0xce0 fs/bcachefs/super-io.c:468
 __bch2_read_super+0x93c/0x12a0 fs/bcachefs/super-io.c:822
 bch2_fs_open+0x3e5/0x1110 fs/bcachefs/super.c:2049
 bch2_mount+0xdcc/0x1130 fs/bcachefs/fs.c:1903
 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
RIP: 0033:0x7f5c3867f3aa
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 de 09 00 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f5c39320ef8 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f5c39320f80 RCX: 00007f5c3867f3aa
RDX: 0000000020011a00 RSI: 0000000020000000 RDI: 00007f5c39320f40
RBP: 0000000020011a00 R08: 00007f5c39320f80 R09: 0000000003a04000
R10: 0000000003a04000 R11: 0000000000000202 R12: 0000000020000000
R13: 00007f5c39320f40 R14: 0000000000011a04 R15: 0000000020000600
 </TASK>

Allocated by task 10315:
 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
 kasan_kmalloc include/linux/kasan.h:211 [inline]
 __do_kmalloc_node mm/slub.c:3966 [inline]
 __kmalloc_node_track_caller+0x220/0x470 mm/slub.c:3986
 __do_krealloc mm/slab_common.c:1192 [inline]
 krealloc+0x5d/0x100 mm/slab_common.c:1225
 bch2_sb_realloc+0x242/0x5d0 fs/bcachefs/super-io.c:189
 read_one_super+0x318/0x12a0 fs/bcachefs/super-io.c:659
 __bch2_read_super+0x4d6/0x12a0 fs/bcachefs/super-io.c:750
 bch2_fs_open+0x3e5/0x1110 fs/bcachefs/super.c:2049
 bch2_mount+0xdcc/0x1130 fs/bcachefs/fs.c:1903
 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

The buggy address belongs to the object at ffff888041d50000
 which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 0 bytes to the right of
 allocated 8192-byte region [ffff888041d50000, ffff888041d52000)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x41d50
head: order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000840(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000840 ffff888015043180 ffffea00012f2200 dead000000000006
raw: 0000000000000000 0000000000020002 00000001ffffffff 0000000000000000
head: 00fff00000000840 ffff888015043180 ffffea00012f2200 dead000000000006
head: 0000000000000000 0000000000020002 00000001ffffffff 0000000000000000
head: 00fff00000000003 ffffea0001075401 dead000000000122 00000000ffffffff
head: 0000000800000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0x1d28c0(GFP_NOWAIT|__GFP_IO|__GFP_FS|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 4906, tgid 1167785533 (dhcpcd), ts 4906, free_ts 95527003222
 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:2175 [inline]
 allocate_slab mm/slub.c:2338 [inline]
 new_slab+0xcc/0x3a0 mm/slub.c:2391
 ___slab_alloc+0x66d/0x1790 mm/slub.c:3525
 __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3610
 __slab_alloc_node mm/slub.c:3663 [inline]
 slab_alloc_node mm/slub.c:3835 [inline]
 __do_kmalloc_node mm/slub.c:3965 [inline]
 __kmalloc_node_track_caller+0x367/0x470 mm/slub.c:3986
 kmalloc_reserve+0xef/0x2c0 net/core/skbuff.c:599
 __alloc_skb+0x164/0x380 net/core/skbuff.c:668
 alloc_skb include/linux/skbuff.h:1313 [inline]
 netlink_dump+0x2b2/0xe00 net/netlink/af_netlink.c:2229
 netlink_recvmsg+0xa0d/0xf30 net/netlink/af_netlink.c:1987
 sock_recvmsg_nosec net/socket.c:1046 [inline]
 sock_recvmsg+0x1f6/0x250 net/socket.c:1068
 ____sys_recvmsg+0x21f/0x6b0 net/socket.c:2803
 ___sys_recvmsg+0x115/0x1a0 net/socket.c:2845
 __sys_recvmsg+0x114/0x1e0 net/socket.c:2875
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcf/0x260 arch/x86/entry/common.c:83
page last free pid 5766 tgid 5766 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1141 [inline]
 free_unref_page_prepare+0x527/0xb10 mm/page_alloc.c:2347
 free_unref_folios+0x256/0xad0 mm/page_alloc.c:2536
 folios_put_refs+0x487/0x6d0 mm/swap.c:1034
 folio_batch_release include/linux/pagevec.h:101 [inline]
 truncate_inode_pages_range+0x334/0xe90 mm/truncate.c:362
 kill_bdev block/bdev.c:85 [inline]
 blkdev_flush_mapping+0x144/0x310 block/bdev.c:644
 blkdev_put_whole+0xc4/0xf0 block/bdev.c:651
 bdev_release+0x487/0x710 block/bdev.c:1075
 blkdev_release+0x15/0x20 block/fops.c:628
 __fput+0x270/0xb80 fs/file_table.c:422
 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

Memory state around the buggy address:
 ffff888041d51f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888041d51f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888041d52000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                   ^
 ffff888041d52080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888041d52100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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