[v5.15] possible deadlock in ext4_evict_inode (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: cc5ec8769306 Linux 5.15.196
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1702d612580000
kernel config: https://syzkaller.appspot.com/x/.config?x=e1bb6d24ef2164eb
dashboard link: https://syzkaller.appspot.com/bug?extid=a3a44cd22b43449e7997
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/c71c660545b2/disk-cc5ec876.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/4f011826cca6/vmlinux-cc5ec876.xz
kernel image: https://storage.googleapis.com/syzbot-assets/8ccd1a2c3f8c/bzImage-cc5ec876.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a3a44c...@syzkaller.appspotmail.com

loop0: detected capacity change from 0 to 128
EXT4-fs (loop0): mounted filesystem without journal. Opts: ,errors=continue. Quota mode: none.
ext4 filesystem being mounted at /31/file1 supports timestamps until 2038-01-19 (0x7fffffff)
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.0.104/4670 is trying to acquire lock:
ffff88801e9b4650 (sb_internal){.+.+}-{0:0}, at: __sb_start_write include/linux/fs.h:1811 [inline]
ffff88801e9b4650 (sb_internal){.+.+}-{0:0}, at: sb_start_intwrite include/linux/fs.h:1928 [inline]
ffff88801e9b4650 (sb_internal){.+.+}-{0:0}, at: ext4_evict_inode+0x444/0x1080 fs/ext4/inode.c:243

but task is already holding lock:
ffff88805e648bd8 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_ext_migrate+0x2c4/0xe50 fs/ext4/migrate.c:438

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&sbi->s_writepages_rwsem){++++}-{0:0}:
percpu_down_read+0x46/0x1b0 include/linux/percpu-rwsem.h:51
ext4_writepages+0x1c0/0x2d20 fs/ext4/inode.c:2689
do_writepages+0x48d/0x6d0 mm/page-writeback.c:2386
__writeback_single_inode+0x153/0xda0 fs/fs-writeback.c:1657
writeback_single_inode+0x221/0x8b0 fs/fs-writeback.c:1770
write_inode_now+0x217/0x280 fs/fs-writeback.c:2811
iput_final fs/inode.c:1756 [inline]
iput+0x5ab/0x8a0 fs/inode.c:1795
ext4_xattr_set_entry+0x10ff/0x3d30 fs/ext4/xattr.c:1837
ext4_xattr_block_set+0x4f7/0x2d30 fs/ext4/xattr.c:1936
ext4_xattr_move_to_block fs/ext4/xattr.c:2633 [inline]
ext4_xattr_make_inode_space fs/ext4/xattr.c:2708 [inline]
ext4_expand_extra_isize_ea+0xf4b/0x19a0 fs/ext4/xattr.c:2800
__ext4_expand_extra_isize+0x301/0x3e0 fs/ext4/inode.c:5901
ext4_try_to_expand_extra_isize fs/ext4/inode.c:5944 [inline]
__ext4_mark_inode_dirty+0x469/0x700 fs/ext4/inode.c:6022
ext4_evict_inode+0xa81/0x1080 fs/ext4/inode.c:282
evict+0x485/0x870 fs/inode.c:647
ext4_orphan_cleanup+0xaa9/0x12e0 fs/ext4/orphan.c:470
ext4_fill_super+0x92f0/0x9a60 fs/ext4/super.c:4975
mount_bdev+0x287/0x3c0 fs/super.c:1400
legacy_get_tree+0xe6/0x180 fs/fs_context.c:611
vfs_get_tree+0x88/0x270 fs/super.c:1530
do_new_mount+0x24a/0xa40 fs/namespace.c:3034
do_mount fs/namespace.c:3377 [inline]
__do_sys_mount fs/namespace.c:3585 [inline]
__se_sys_mount+0x2d6/0x3c0 fs/namespace.c:3562
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #0 (sb_internal){.+.+}-{0:0}:
check_prev_add kernel/locking/lockdep.c:3053 [inline]
check_prevs_add kernel/locking/lockdep.c:3172 [inline]
validate_chain kernel/locking/lockdep.c:3788 [inline]
__lock_acquire+0x2c33/0x7c60 kernel/locking/lockdep.c:5012
lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623
percpu_down_read+0x46/0x1b0 include/linux/percpu-rwsem.h:51
__sb_start_write include/linux/fs.h:1811 [inline]
sb_start_intwrite include/linux/fs.h:1928 [inline]
ext4_evict_inode+0x444/0x1080 fs/ext4/inode.c:243
evict+0x485/0x870 fs/inode.c:647
ext4_ext_migrate+0xc0a/0xe50 fs/ext4/migrate.c:588
__ext4_ioctl fs/ext4/ioctl.c:1028 [inline]
ext4_ioctl+0x18a5/0x3590 fs/ext4/ioctl.c:1282
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&sbi->s_writepages_rwsem);
lock(sb_internal);
lock(&sbi->s_writepages_rwsem);
lock(sb_internal);

*** DEADLOCK ***

3 locks held by syz.0.104/4670:
#0: ffff88801e9b4460 (sb_writers#5){.+.+}-{0:0}, at: mnt_want_write_file+0x5c/0x200 fs/namespace.c:430
#1: ffff88806012bfc0 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: inode_lock include/linux/fs.h:787 [inline]
#1: ffff88806012bfc0 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: __ext4_ioctl fs/ext4/ioctl.c:1027 [inline]
#1: ffff88806012bfc0 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: ext4_ioctl+0x189d/0x3590 fs/ext4/ioctl.c:1282
#2: ffff88805e648bd8 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_ext_migrate+0x2c4/0xe50 fs/ext4/migrate.c:438

stack backtrace:
CPU: 0 PID: 4670 Comm: syz.0.104 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Call Trace:
<TASK>
dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
check_noncircular+0x274/0x310 kernel/locking/lockdep.c:2133
check_prev_add kernel/locking/lockdep.c:3053 [inline]
check_prevs_add kernel/locking/lockdep.c:3172 [inline]
validate_chain kernel/locking/lockdep.c:3788 [inline]
__lock_acquire+0x2c33/0x7c60 kernel/locking/lockdep.c:5012
lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623
percpu_down_read+0x46/0x1b0 include/linux/percpu-rwsem.h:51
__sb_start_write include/linux/fs.h:1811 [inline]
sb_start_intwrite include/linux/fs.h:1928 [inline]
ext4_evict_inode+0x444/0x1080 fs/ext4/inode.c:243
evict+0x485/0x870 fs/inode.c:647
ext4_ext_migrate+0xc0a/0xe50 fs/ext4/migrate.c:588
__ext4_ioctl fs/ext4/ioctl.c:1028 [inline]
ext4_ioctl+0x18a5/0x3590 fs/ext4/ioctl.c:1282
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f5956191749
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f59543d7038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f59563e8090 RCX: 00007f5956191749
RDX: 0000000000000000 RSI: 0000000000006609 RDI: 0000000000000007
RBP: 00007f5956215f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f59563e8128 R14: 00007f59563e8090 R15: 00007ffc0593e508
</TASK>


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