Re: [syzbot] [f2fs?] kernel BUG in folio_end_read (3)

[Chao Yu <chao@kernel.org>]

#syz fix f2fs: avoid reading already updated pages during GC

On 4/14/2026 11:11 AM, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    a55f7f5f29b3 Merge tag 'net-7.0-rc8' of git://git.kernel.o..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=15cc7bd6580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=d46eab0cfd31c214
> dashboard link: https://syzkaller.appspot.com/bug?extid=337ec6af661bd91fa43a
> compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
> 
> Unfortunately, I don't have any reproducer for this issue yet.
> 
> Downloadable assets:
> disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-a55f7f5f.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/6392912f99d3/vmlinux-a55f7f5f.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/9d6fd8c7dfa0/bzImage-a55f7f5f.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+337ec6af661bd91fa43a@syzkaller.appspotmail.com
> 
> page: refcount:2 mapcount:0 mapping:ffff888046f3e788 index:0x1507 pfn:0x32d0e
> memcg:ffff88801c6c8d40
> aops:f2fs_meta_aops ino:2
> flags: 0x4fff400000000a9(locked|waiters|uptodate|lru|node=1|zone=1|lastcpupid=0x7ff)
> raw: 04fff400000000a9 ffffea0000d1b988 ffff888030450a80 ffff888046f3e788
> raw: 0000000000001507 0000000000000000 00000002ffffffff ffff88801c6c8d40
> page dumped because: VM_BUG_ON_FOLIO(success && folio_test_uptodate(folio))
> page_owner tracks the page as allocated
> page last allocated via order 0, migratetype Unmovable, gfp_mask 0x40c40(GFP_NOFS|__GFP_COMP), pid 5318, tgid 5316 (syz.0.0), ts 76502021566, free_ts 42035680990
>   set_page_owner include/linux/page_owner.h:32 [inline]
>   post_alloc_hook+0x231/0x280 mm/page_alloc.c:1889
>   prep_new_page mm/page_alloc.c:1897 [inline]
>   get_page_from_freelist+0x24dc/0x2580 mm/page_alloc.c:3962
>   __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5250
>   alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2490
>   alloc_frozen_pages_noprof mm/mempolicy.c:2561 [inline]
>   alloc_pages_noprof+0xa8/0x1a0 mm/mempolicy.c:2581
>   folio_alloc_noprof+0x1e/0x30 mm/mempolicy.c:2591
>   filemap_alloc_folio_noprof+0x111/0x470 mm/filemap.c:1013
>   __filemap_get_folio_mpol+0x3fc/0xb00 mm/filemap.c:2011
>   __filemap_get_folio include/linux/pagemap.h:763 [inline]
>   f2fs_filemap_get_folio fs/f2fs/f2fs.h:3065 [inline]
>   ra_data_block+0x544/0xd00 fs/f2fs/gc.c:1277
>   gc_data_segment fs/f2fs/gc.c:1648 [inline]
>   do_garbage_collect+0x358d/0x7080 fs/f2fs/gc.c:1874
>   f2fs_gc+0xca2/0x2570 fs/f2fs/gc.c:1981
>   f2fs_balance_fs+0x657/0x840 fs/f2fs/segment.c:467
>   f2fs_map_blocks+0x2958/0x4340 fs/f2fs/data.c:1826
>   f2fs_iomap_begin+0x3bd/0x8f0 fs/f2fs/data.c:4527
>   iomap_iter+0x600/0x1020 fs/iomap/iter.c:110
>   __iomap_dio_rw+0x1360/0x1ea0 fs/iomap/direct-io.c:795
> page last free pid 15 tgid 15 stack trace:
>   reset_page_owner include/linux/page_owner.h:25 [inline]
>   __free_pages_prepare mm/page_alloc.c:1433 [inline]
>   __free_frozen_pages+0xc2b/0xdb0 mm/page_alloc.c:2978
>   __tlb_remove_table_free mm/mmu_gather.c:228 [inline]
>   tlb_remove_table_rcu+0x85/0x100 mm/mmu_gather.c:291
>   rcu_do_batch kernel/rcu/tree.c:2617 [inline]
>   rcu_core+0x7cd/0x1070 kernel/rcu/tree.c:2869
>   handle_softirqs+0x22a/0x870 kernel/softirq.c:622
>   run_ksoftirqd+0x36/0x60 kernel/softirq.c:1063
>   smpboot_thread_fn+0x541/0xa50 kernel/smpboot.c:160
>   kthread+0x388/0x470 kernel/kthread.c:436
>   ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
>   ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
> ------------[ cut here ]------------
> kernel BUG at mm/filemap.c:1536!
> Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
> CPU: 0 UID: 0 PID: 42 Comm: kworker/u4:3 Not tainted syzkaller #0 PREEMPT(full)
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
> Workqueue: loop0 loop_workfn
> RIP: 0010:folio_end_read+0x22e/0x230 mm/filemap.c:1536
> Code: 6f c3 ff 48 89 df 48 c7 c6 e0 c4 d7 8b e8 ba ba 25 ff 90 0f 0b e8 02 6f c3 ff 48 89 df 48 c7 c6 40 bb d7 8b e8 a3 ba 25 ff 90 <0f> 0b 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa
> RSP: 0018:ffffc90000447478 EFLAGS: 00010246
> RAX: b965f80585da9300 RBX: ffffea0000cb4380 RCX: 0000000000000000
> RDX: 0000000000000006 RSI: ffffffff8deff28a RDI: 00000000ffffffff
> RBP: 0000000000000001 R08: ffffffff9011feb7 R09: 1ffffffff2023fd6
> R10: dffffc0000000000 R11: fffffbfff2023fd7 R12: 1ffffd4000196871
> R13: 1ffffd4000196870 R14: ffffea0000cb4388 R15: 0000000000000008
> FS:  0000000000000000(0000) GS:ffff88808ca49000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f8b147ff000 CR3: 0000000038c3d000 CR4: 0000000000352ef0
> Call Trace:
>   <TASK>
>   f2fs_finish_read_bio+0x4fc/0x940 fs/f2fs/data.c:182
>   blk_update_request+0x57e/0xe60 block/blk-mq.c:1016
>   blk_mq_end_request+0x3e/0x70 block/blk-mq.c:1178
>   lo_rw_aio_complete drivers/block/loop.c:337 [inline]
>   lo_rw_aio+0xcde/0xf00 drivers/block/loop.c:409
>   do_req_filebacked drivers/block/loop.c:435 [inline]
>   loop_handle_cmd drivers/block/loop.c:1925 [inline]
>   loop_process_work+0x958/0x11a0 drivers/block/loop.c:1960
>   process_one_work kernel/workqueue.c:3276 [inline]
>   process_scheduled_works+0xb6e/0x18c0 kernel/workqueue.c:3359
>   worker_thread+0xa53/0xfc0 kernel/workqueue.c:3440
>   kthread+0x388/0x470 kernel/kthread.c:436
>   ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
>   ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
>   </TASK>
> Modules linked in:
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:folio_end_read+0x22e/0x230 mm/filemap.c:1536
> Code: 6f c3 ff 48 89 df 48 c7 c6 e0 c4 d7 8b e8 ba ba 25 ff 90 0f 0b e8 02 6f c3 ff 48 89 df 48 c7 c6 40 bb d7 8b e8 a3 ba 25 ff 90 <0f> 0b 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa
> RSP: 0018:ffffc90000447478 EFLAGS: 00010246
> RAX: b965f80585da9300 RBX: ffffea0000cb4380 RCX: 0000000000000000
> RDX: 0000000000000006 RSI: ffffffff8deff28a RDI: 00000000ffffffff
> RBP: 0000000000000001 R08: ffffffff9011feb7 R09: 1ffffffff2023fd6
> R10: dffffc0000000000 R11: fffffbfff2023fd7 R12: 1ffffd4000196871
> R13: 1ffffd4000196870 R14: ffffea0000cb4388 R15: 0000000000000008
> FS:  0000000000000000(0000) GS:ffff88808ca49000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f8b147ff000 CR3: 0000000038c3d000 CR4: 0000000000352ef0
> 
> 
> ---
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