syzbot

======================================================
WARNING: possible circular locking dependency detected
6.15.0-rc4-syzkaller-00042-gb6ea1680d0ac #0 Not tainted
------------------------------------------------------
syz.7.264/8325 is trying to acquire lock:
ffff8880514b0610 (sb_internal#4){.+.+}-{0:0}, at: nilfs_page_mkwrite+0x8b0/0xc20 fs/nilfs2/file.c:95

but task is already holding lock:
ffff8880514b0518 (sb_pagefaults#6){.+.+}-{0:0}, at: do_page_mkwrite+0x14a/0x310 mm/memory.c:3287

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #5 (sb_pagefaults#6){.+.+}-{0:0}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866
       percpu_down_read include/linux/percpu-rwsem.h:52 [inline]
       __sb_start_write include/linux/fs.h:1783 [inline]
       sb_start_pagefault include/linux/fs.h:1948 [inline]
       nilfs_page_mkwrite+0x21e/0xc20 fs/nilfs2/file.c:57
       do_page_mkwrite+0x14a/0x310 mm/memory.c:3287
       do_shared_fault mm/memory.c:5594 [inline]
       do_fault mm/memory.c:5656 [inline]
       do_pte_missing mm/memory.c:4160 [inline]
       handle_pte_fault mm/memory.c:5997 [inline]
       __handle_mm_fault+0x18d2/0x5380 mm/memory.c:6140
       handle_mm_fault+0x2d5/0x7f0 mm/memory.c:6309
       do_user_addr_fault+0x764/0x1390 arch/x86/mm/fault.c:1388
       handle_page_fault arch/x86/mm/fault.c:1480 [inline]
       exc_page_fault+0x68/0x110 arch/x86/mm/fault.c:1538
       asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623

-> #4 (&mm->mmap_lock){++++}-{4:4}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866
       __might_fault+0xcc/0x130 mm/memory.c:7151
       _copy_to_iter+0xf3/0x15a0 lib/iov_iter.c:184
       copy_page_to_iter+0xa7/0x150 lib/iov_iter.c:362
       copy_folio_to_iter include/linux/uio.h:198 [inline]
       filemap_read+0x78d/0x11d0 mm/filemap.c:2753
       blkdev_read_iter+0x30a/0x440 block/fops.c:809
       new_sync_read fs/read_write.c:489 [inline]
       vfs_read+0x4cd/0x980 fs/read_write.c:570
       ksys_read+0x145/0x250 fs/read_write.c:713
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #3 (&sb->s_type->i_mutex_key#7){++++}-{4:4}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866
       down_write+0x96/0x1f0 kernel/locking/rwsem.c:1577
       inode_lock include/linux/fs.h:867 [inline]
       set_blocksize+0x23b/0x500 block/bdev.c:203
       sb_set_blocksize block/bdev.c:224 [inline]
       sb_min_blocksize+0x119/0x210 block/bdev.c:239
       init_nilfs+0x43/0x690 fs/nilfs2/the_nilfs.c:710
       nilfs_fill_super+0x8f/0x650 fs/nilfs2/super.c:1060
       nilfs_get_tree+0x4f4/0x870 fs/nilfs2/super.c:1228
       vfs_get_tree+0x8f/0x2b0 fs/super.c:1759
       do_new_mount+0x24a/0xa40 fs/namespace.c:3884
       do_mount fs/namespace.c:4224 [inline]
       __do_sys_mount fs/namespace.c:4435 [inline]
       __se_sys_mount+0x317/0x410 fs/namespace.c:4412
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (&nilfs->ns_sem){++++}-{4:4}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866
       down_write+0x96/0x1f0 kernel/locking/rwsem.c:1577
       nilfs_set_error fs/nilfs2/super.c:92 [inline]
       __nilfs_error+0x1ca/0x4b0 fs/nilfs2/super.c:141
       nilfs_bmap_convert_error fs/nilfs2/bmap.c:35 [inline]
       nilfs_bmap_propagate+0x108/0x130 fs/nilfs2/bmap.c:332
       nilfs_segctor_apply_buffers+0x161/0x330 fs/nilfs2/segment.c:1010
       nilfs_segctor_scan_file+0x6fe/0x8e0 fs/nilfs2/segment.c:1070
       nilfs_segctor_collect_blocks fs/nilfs2/segment.c:1221 [inline]
       nilfs_segctor_collect fs/nilfs2/segment.c:1547 [inline]
       nilfs_segctor_do_construct+0x1b9d/0x6970 fs/nilfs2/segment.c:2122
       nilfs_segctor_construct+0x17b/0x690 fs/nilfs2/segment.c:2478
       nilfs_segctor_thread_construct fs/nilfs2/segment.c:2586 [inline]
       nilfs_segctor_thread+0x6f7/0xe00 fs/nilfs2/segment.c:2700
       kthread+0x70e/0x8a0 kernel/kthread.c:464
       ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:153
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #1 (&nilfs->ns_segctor_sem){++++}-{4:4}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866
       down_read+0x46/0x2e0 kernel/locking/rwsem.c:1524
       nilfs_transaction_begin+0x365/0x710 fs/nilfs2/segment.c:221
       nilfs_setattr+0x10f/0x2b0 fs/nilfs2/inode.c:912
       notify_change+0xb33/0xe40 fs/attr.c:552
       chmod_common+0x24f/0x3f0 fs/open.c:644
       do_fchmodat+0x12d/0x200 fs/open.c:690
       __do_sys_fchmodat fs/open.c:709 [inline]
       __se_sys_fchmodat fs/open.c:706 [inline]
       __x64_sys_fchmodat+0x7d/0x90 fs/open.c:706
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (sb_internal#4){.+.+}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3166 [inline]
       check_prevs_add kernel/locking/lockdep.c:3285 [inline]
       validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3909
       __lock_acquire+0xaac/0xd20 kernel/locking/lockdep.c:5235
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866
       percpu_down_read include/linux/percpu-rwsem.h:52 [inline]
       __sb_start_write include/linux/fs.h:1783 [inline]
       sb_start_intwrite include/linux/fs.h:1966 [inline]
       nilfs_transaction_begin+0x268/0x710 fs/nilfs2/segment.c:218
       nilfs_page_mkwrite+0x8b0/0xc20 fs/nilfs2/file.c:95
       do_page_mkwrite+0x14a/0x310 mm/memory.c:3287
       do_shared_fault mm/memory.c:5594 [inline]
       do_fault mm/memory.c:5656 [inline]
       do_pte_missing mm/memory.c:4160 [inline]
       handle_pte_fault mm/memory.c:5997 [inline]
       __handle_mm_fault+0x18d2/0x5380 mm/memory.c:6140
       handle_mm_fault+0x2d5/0x7f0 mm/memory.c:6309
       do_user_addr_fault+0x764/0x1390 arch/x86/mm/fault.c:1388
       handle_page_fault arch/x86/mm/fault.c:1480 [inline]
       exc_page_fault+0x68/0x110 arch/x86/mm/fault.c:1538
       asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623

other info that might help us debug this:

Chain exists of:
  sb_internal#4 --> &mm->mmap_lock --> sb_pagefaults#6

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  rlock(sb_pagefaults#6);
                               lock(&mm->mmap_lock);
                               lock(sb_pagefaults#6);
  rlock(sb_internal#4);

 *** DEADLOCK ***

2 locks held by syz.7.264/8325:
 #0: ffff88802c3429e0 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_trylock include/linux/mmap_lock.h:203 [inline]
 #0: ffff88802c3429e0 (&mm->mmap_lock){++++}-{4:4}, at: get_mmap_lock_carefully mm/memory.c:6346 [inline]
 #0: ffff88802c3429e0 (&mm->mmap_lock){++++}-{4:4}, at: lock_mm_and_find_vma+0x32/0x300 mm/memory.c:6406
 #1: ffff8880514b0518 (sb_pagefaults#6){.+.+}-{0:0}, at: do_page_mkwrite+0x14a/0x310 mm/memory.c:3287

stack backtrace:
CPU: 1 UID: 0 PID: 8325 Comm: syz.7.264 Not tainted 6.15.0-rc4-syzkaller-00042-gb6ea1680d0ac #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2079
 check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2211
 check_prev_add kernel/locking/lockdep.c:3166 [inline]
 check_prevs_add kernel/locking/lockdep.c:3285 [inline]
 validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3909
 __lock_acquire+0xaac/0xd20 kernel/locking/lockdep.c:5235
 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866
 percpu_down_read include/linux/percpu-rwsem.h:52 [inline]
 __sb_start_write include/linux/fs.h:1783 [inline]
 sb_start_intwrite include/linux/fs.h:1966 [inline]
 nilfs_transaction_begin+0x268/0x710 fs/nilfs2/segment.c:218
 nilfs_page_mkwrite+0x8b0/0xc20 fs/nilfs2/file.c:95
 do_page_mkwrite+0x14a/0x310 mm/memory.c:3287
 do_shared_fault mm/memory.c:5594 [inline]
 do_fault mm/memory.c:5656 [inline]
 do_pte_missing mm/memory.c:4160 [inline]
 handle_pte_fault mm/memory.c:5997 [inline]
 __handle_mm_fault+0x18d2/0x5380 mm/memory.c:6140
 handle_mm_fault+0x2d5/0x7f0 mm/memory.c:6309
 do_user_addr_fault+0x764/0x1390 arch/x86/mm/fault.c:1388
 handle_page_fault arch/x86/mm/fault.c:1480 [inline]
 exc_page_fault+0x68/0x110 arch/x86/mm/fault.c:1538
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
RIP: 0033:0x7f3081b5669d
Code: c3 66 66 2e 0f 1f 84 00 00 00 00 00 90 83 fa 10 73 2d 83 fa 08 73 46 83 fa 04 73 16 83 fa 01 7c 10 8a 0e 74 0a 0f b7 74 16 fe <66> 89 74 17 fe 88 0f c3 8b 4c 16 fc 8b 36 89 4c 17 fc 89 37 c3 c5
RSP: 002b:00007fff57339808 EFLAGS: 00010202
RAX: 0000200000000000 RBX: 0000000000000004 RCX: 800000000000002e
RDX: 0000000000000002 RSI: 000000000000002e RDI: 0000200000000000
RBP: 00007f3081db7ba0 R08: 00007f3081a00000 R09: 0000000000000001
R10: 0000000000000001 R11: 0000000000000009 R12: 00007f3081db624c
R13: 00007f3081db6240 R14: fffffffffffffffe R15: 00007fff57339920
 </TASK>