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Date: Sun, 19 May 2024 04:16:31 +0900
From: Ryusuke Konishi <konishi.ryusuke@...il.com>
To: syzbot <syzbot+77c39f023a0cb2e4c149@...kaller.appspotmail.com>
Cc: linux-kernel@...r.kernel.org, linux-nilfs@...r.kernel.org,
syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [nilfs?] possible deadlock in nilfs_transaction_begin
On Sat, May 18, 2024 at 9:29 PM syzbot
<syzbot+77c39f023a0cb2e4c149@...kaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: a5131c3fdf26 Merge tag 'x86-shstk-2024-05-13' of git://git..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=144c6e04980000
> kernel config: https://syzkaller.appspot.com/x/.config?x=fdb182f40cdd66f7
> dashboard link: https://syzkaller.appspot.com/bug?extid=77c39f023a0cb2e4c149
> compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> userspace arch: i386
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> Downloadable assets:
> disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-a5131c3f.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/6d23116dab9c/vmlinux-a5131c3f.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/dd8b9de9af4f/bzImage-a5131c3f.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+77c39f023a0cb2e4c149@...kaller.appspotmail.com
>
> NILFS (loop2): inode bitmap is inconsistent for reserved inodes
> NILFS (loop2): repaired inode bitmap for reserved inodes
> ======================================================
> WARNING: possible circular locking dependency detected
> 6.9.0-syzkaller-01768-ga5131c3fdf26 #0 Not tainted
> ------------------------------------------------------
> syz-executor.2/23478 is trying to acquire lock:
> ffffffff8d938460 (fs_reclaim){+.+.}-{0:0}, at: might_alloc include/linux/sched/mm.h:312 [inline]
> ffffffff8d938460 (fs_reclaim){+.+.}-{0:0}, at: prepare_alloc_pages.constprop.0+0x155/0x560 mm/page_alloc.c:4346
>
> but task is already holding lock:
> ffff888026c5c2a0 (&nilfs->ns_segctor_sem){++++}-{3:3}, at: nilfs_transaction_begin+0x326/0xa40 fs/nilfs2/segment.c:223
>
> which lock already depends on the new lock.
>
>
> the existing dependency chain (in reverse order) is:
>
> -> #2 (&nilfs->ns_segctor_sem){++++}-{3:3}:
> down_read+0x9a/0x330 kernel/locking/rwsem.c:1526
> nilfs_transaction_begin+0x326/0xa40 fs/nilfs2/segment.c:223
> nilfs_create+0xb7/0x320 fs/nilfs2/namei.c:82
> lookup_open.isra.0+0x10a1/0x13c0 fs/namei.c:3505
> open_last_lookups fs/namei.c:3574 [inline]
> path_openat+0x92f/0x2990 fs/namei.c:3804
> do_filp_open+0x1dc/0x430 fs/namei.c:3834
> do_sys_openat2+0x17a/0x1e0 fs/open.c:1406
> do_sys_open fs/open.c:1421 [inline]
> __do_compat_sys_openat fs/open.c:1481 [inline]
> __se_compat_sys_openat fs/open.c:1479 [inline]
> __ia32_compat_sys_openat+0x16e/0x210 fs/open.c:1479
> do_syscall_32_irqs_on arch/x86/entry/common.c:165 [inline]
> __do_fast_syscall_32+0x75/0x120 arch/x86/entry/common.c:386
> do_fast_syscall_32+0x32/0x80 arch/x86/entry/common.c:411
> entry_SYSENTER_compat_after_hwframe+0x84/0x8e
>
> -> #1 (sb_internal#5){.+.+}-{0:0}:
> percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
> __sb_start_write include/linux/fs.h:1661 [inline]
> sb_start_intwrite include/linux/fs.h:1844 [inline]
> nilfs_transaction_begin+0x21b/0xa40 fs/nilfs2/segment.c:220
> nilfs_dirty_inode+0x1a4/0x270 fs/nilfs2/inode.c:1153
> __mark_inode_dirty+0x1f0/0xe70 fs/fs-writeback.c:2486
> mark_inode_dirty_sync include/linux/fs.h:2426 [inline]
> iput.part.0+0x5b/0x7f0 fs/inode.c:1764
> iput+0x5c/0x80 fs/inode.c:1757
> dentry_unlink_inode+0x295/0x440 fs/dcache.c:400
> __dentry_kill+0x1d0/0x600 fs/dcache.c:603
> shrink_kill fs/dcache.c:1048 [inline]
> shrink_dentry_list+0x140/0x5d0 fs/dcache.c:1075
> prune_dcache_sb+0xeb/0x150 fs/dcache.c:1156
> super_cache_scan+0x32a/0x550 fs/super.c:221
> do_shrink_slab+0x44f/0x11c0 mm/shrinker.c:435
> shrink_slab_memcg mm/shrinker.c:548 [inline]
> shrink_slab+0xa87/0x1310 mm/shrinker.c:626
> shrink_one+0x493/0x7c0 mm/vmscan.c:4774
> shrink_many mm/vmscan.c:4835 [inline]
> lru_gen_shrink_node+0x89f/0x1750 mm/vmscan.c:4935
> shrink_node mm/vmscan.c:5894 [inline]
> kswapd_shrink_node mm/vmscan.c:6704 [inline]
> balance_pgdat+0x10d1/0x1a10 mm/vmscan.c:6895
> kswapd+0x5ea/0xbf0 mm/vmscan.c:7164
> kthread+0x2c1/0x3a0 kernel/kthread.c:388
> ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
> ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
>
> -> #0 (fs_reclaim){+.+.}-{0:0}:
> check_prev_add kernel/locking/lockdep.c:3134 [inline]
> check_prevs_add kernel/locking/lockdep.c:3253 [inline]
> validate_chain kernel/locking/lockdep.c:3869 [inline]
> __lock_acquire+0x2478/0x3b30 kernel/locking/lockdep.c:5137
> lock_acquire kernel/locking/lockdep.c:5754 [inline]
> lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5719
> __fs_reclaim_acquire mm/page_alloc.c:3698 [inline]
> fs_reclaim_acquire+0x102/0x160 mm/page_alloc.c:3712
> might_alloc include/linux/sched/mm.h:312 [inline]
> prepare_alloc_pages.constprop.0+0x155/0x560 mm/page_alloc.c:4346
> __alloc_pages+0x194/0x2460 mm/page_alloc.c:4564
> alloc_pages_mpol+0x275/0x610 mm/mempolicy.c:2264
> folio_alloc+0x1e/0x40 mm/mempolicy.c:2342
> filemap_alloc_folio+0x3ba/0x490 mm/filemap.c:984
> __filemap_get_folio+0x527/0xa90 mm/filemap.c:1926
> pagecache_get_page+0x2c/0x260 mm/folio-compat.c:93
> block_write_begin+0x38/0x4a0 fs/buffer.c:2209
> nilfs_write_begin+0x9f/0x1a0 fs/nilfs2/inode.c:262
> page_symlink+0x356/0x450 fs/namei.c:5236
> nilfs_symlink+0x23c/0x3c0 fs/nilfs2/namei.c:153
> vfs_symlink fs/namei.c:4489 [inline]
> vfs_symlink+0x3e8/0x630 fs/namei.c:4473
> do_symlinkat+0x263/0x310 fs/namei.c:4515
> __do_sys_symlink fs/namei.c:4536 [inline]
> __se_sys_symlink fs/namei.c:4534 [inline]
> __ia32_sys_symlink+0x78/0xa0 fs/namei.c:4534
> do_syscall_32_irqs_on arch/x86/entry/common.c:165 [inline]
> __do_fast_syscall_32+0x75/0x120 arch/x86/entry/common.c:386
> do_fast_syscall_32+0x32/0x80 arch/x86/entry/common.c:411
> entry_SYSENTER_compat_after_hwframe+0x84/0x8e
>
> other info that might help us debug this:
>
> Chain exists of:
> fs_reclaim --> sb_internal#5 --> &nilfs->ns_segctor_sem
>
> Possible unsafe locking scenario:
>
> CPU0 CPU1
> ---- ----
> rlock(&nilfs->ns_segctor_sem);
> lock(sb_internal#5);
> lock(&nilfs->ns_segctor_sem);
> lock(fs_reclaim);
>
> *** DEADLOCK ***
>
> 4 locks held by syz-executor.2/23478:
> #0: ffff888000c0c420 (sb_writers#32){.+.+}-{0:0}, at: filename_create+0x10d/0x530 fs/namei.c:3893
> #1: ffff88804b284f88 (&type->i_mutex_dir_key#23/1){+.+.}-{3:3}, at: inode_lock_nested include/linux/fs.h:826 [inline]
> #1: ffff88804b284f88 (&type->i_mutex_dir_key#23/1){+.+.}-{3:3}, at: filename_create+0x1c2/0x530 fs/namei.c:3900
> #2: ffff888000c0c610 (sb_internal#5){.+.+}-{0:0}, at: nilfs_symlink+0x114/0x3c0 fs/nilfs2/namei.c:140
> #3: ffff888026c5c2a0 (&nilfs->ns_segctor_sem){++++}-{3:3}, at: nilfs_transaction_begin+0x326/0xa40 fs/nilfs2/segment.c:223
>
> stack backtrace:
> CPU: 2 PID: 23478 Comm: syz-executor.2 Not tainted 6.9.0-syzkaller-01768-ga5131c3fdf26 #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
> check_noncircular+0x31a/0x400 kernel/locking/lockdep.c:2187
> check_prev_add kernel/locking/lockdep.c:3134 [inline]
> check_prevs_add kernel/locking/lockdep.c:3253 [inline]
> validate_chain kernel/locking/lockdep.c:3869 [inline]
> __lock_acquire+0x2478/0x3b30 kernel/locking/lockdep.c:5137
> lock_acquire kernel/locking/lockdep.c:5754 [inline]
> lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5719
> __fs_reclaim_acquire mm/page_alloc.c:3698 [inline]
> fs_reclaim_acquire+0x102/0x160 mm/page_alloc.c:3712
> might_alloc include/linux/sched/mm.h:312 [inline]
> prepare_alloc_pages.constprop.0+0x155/0x560 mm/page_alloc.c:4346
> __alloc_pages+0x194/0x2460 mm/page_alloc.c:4564
> alloc_pages_mpol+0x275/0x610 mm/mempolicy.c:2264
> folio_alloc+0x1e/0x40 mm/mempolicy.c:2342
> filemap_alloc_folio+0x3ba/0x490 mm/filemap.c:984
> __filemap_get_folio+0x527/0xa90 mm/filemap.c:1926
> pagecache_get_page+0x2c/0x260 mm/folio-compat.c:93
> block_write_begin+0x38/0x4a0 fs/buffer.c:2209
> nilfs_write_begin+0x9f/0x1a0 fs/nilfs2/inode.c:262
> page_symlink+0x356/0x450 fs/namei.c:5236
> nilfs_symlink+0x23c/0x3c0 fs/nilfs2/namei.c:153
> vfs_symlink fs/namei.c:4489 [inline]
> vfs_symlink+0x3e8/0x630 fs/namei.c:4473
> do_symlinkat+0x263/0x310 fs/namei.c:4515
> __do_sys_symlink fs/namei.c:4536 [inline]
> __se_sys_symlink fs/namei.c:4534 [inline]
> __ia32_sys_symlink+0x78/0xa0 fs/namei.c:4534
> do_syscall_32_irqs_on arch/x86/entry/common.c:165 [inline]
> __do_fast_syscall_32+0x75/0x120 arch/x86/entry/common.c:386
> do_fast_syscall_32+0x32/0x80 arch/x86/entry/common.c:411
> entry_SYSENTER_compat_after_hwframe+0x84/0x8e
> RIP: 0023:0xf734f579
> Code: b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 00 00 00 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00
> RSP: 002b:00000000f5f415ac EFLAGS: 00000292 ORIG_RAX: 0000000000000053
> RAX: ffffffffffffffda RBX: 0000000020000340 RCX: 0000000020000100
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000292 R12: 0000000000000000
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
> </TASK>
> ----------------
> Code disassembly (best guess), 2 bytes skipped:
> 0: 10 06 adc %al,(%rsi)
> 2: 03 74 b4 01 add 0x1(%rsp,%rsi,4),%esi
> 6: 10 07 adc %al,(%rdi)
> 8: 03 74 b0 01 add 0x1(%rax,%rsi,4),%esi
> c: 10 08 adc %cl,(%rax)
> e: 03 74 d8 01 add 0x1(%rax,%rbx,8),%esi
> 1e: 00 51 52 add %dl,0x52(%rcx)
> 21: 55 push %rbp
> 22: 89 e5 mov %esp,%ebp
> 24: 0f 34 sysenter
> 26: cd 80 int $0x80
> * 28: 5d pop %rbp <-- trapping instruction
> 29: 5a pop %rdx
> 2a: 59 pop %rcx
> 2b: c3 ret
> 2c: 90 nop
> 2d: 90 nop
> 2e: 90 nop
> 2f: 90 nop
> 30: 8d b4 26 00 00 00 00 lea 0x0(%rsi,%riz,1),%esi
> 37: 8d b4 26 00 00 00 00 lea 0x0(%rsi,%riz,1),%esi
>
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@...glegroups.com.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>
> If the report is already addressed, let syzbot know by replying with:
> #syz fix: exact-commit-title
>
> If you want to overwrite report's subsystems, reply with:
> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
>
> If the report is a duplicate of another one, reply with:
> #syz dup: exact-subject-of-another-report
>
> If you want to undo deduplication, reply with:
> #syz undup
This issue seems to be the same as the report below, but I don't have
time to look into it in detail right now, so I'll put it on hold.
https://syzkaller.appspot.com/bug?extid=ca73f5a22aec76875d85
It looks like the GFP flags in the symlink's page cache allocation are
causing the circular lock dependency.
Ryusuke Konishi
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