[syzbot] [nilfs?] possible deadlock in nilfs_transaction_begin

From: syzbot
Date: Sat May 18 2024 - 08:29:48 EST

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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@xxxxxxxxxxxxxxxxxxxxxxxxx

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

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