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From: syzbot <syzbot+d3bb749184481f92deb5@syzkaller.appspotmail.com>
To: hdanton@sina.com, linux-kernel@vger.kernel.org,
	syzkaller-bugs@googlegroups.com
Subject: Re: [syzbot] [ext4?] possible deadlock in ext4_find_inline_entry
Date: Wed, 28 Dec 2022 17:23:22 -0800	[thread overview]
Message-ID: <000000000000b5e7b405f0ed54fb@google.com> (raw)
In-Reply-To: <20221229005540.2777-1-hdanton@sina.com>

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
possible deadlock in ext4_xattr_set_entry

EXT4-fs: Warning: mounting with an experimental mount option 'dioread_nolock' for blocksize < PAGE_SIZE
EXT4-fs (loop0): mounted filesystem without journal. Quota mode: none.
======================================================
WARNING: possible circular locking dependency detected
6.1.0-rc8-syzkaller-00172-ga5541c0811a0-dirty #0 Not tainted
------------------------------------------------------
syz-executor.0/3668 is trying to acquire lock:
ffff0000cf16bd60 (&sb->s_type->i_mutex_key#8){++++}-{3:3}, at: inode_lock include/linux/fs.h:756 [inline]
ffff0000cf16bd60 (&sb->s_type->i_mutex_key#8){++++}-{3:3}, at: ext4_xattr_inode_create fs/ext4/xattr.c:1453 [inline]
ffff0000cf16bd60 (&sb->s_type->i_mutex_key#8){++++}-{3:3}, at: ext4_xattr_inode_lookup_create fs/ext4/xattr.c:1536 [inline]
ffff0000cf16bd60 (&sb->s_type->i_mutex_key#8){++++}-{3:3}, at: ext4_xattr_set_entry+0xdbc/0xe00 fs/ext4/xattr.c:1664

but task is already holding lock:
ffff0000cf16b098 (&ei->xattr_sem){++++}-{3:3}, at: ext4_write_lock_xattr fs/ext4/xattr.h:155 [inline]
ffff0000cf16b098 (&ei->xattr_sem){++++}-{3:3}, at: ext4_xattr_set_handle+0xd0/0x9a0 fs/ext4/xattr.c:2308

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&ei->xattr_sem){++++}-{3:3}:
       down_read+0x5c/0x78 kernel/locking/rwsem.c:1509
       ext4_xattr_get+0x90/0x418 fs/ext4/xattr.c:665
       ext4_xattr_security_get+0x40/0x54 fs/ext4/xattr_security.c:20
       __vfs_getxattr+0x1fc/0x20c fs/xattr.c:407
       cap_inode_need_killpriv+0x34/0x5c security/commoncap.c:301
       security_inode_need_killpriv+0x34/0x88 security/security.c:1422
       dentry_needs_remove_privs fs/inode.c:1995 [inline]
       __file_remove_privs+0xe0/0x308 fs/inode.c:2026
       file_modified_flags+0x60/0x330 fs/inode.c:2148
       file_modified+0x24/0x34 fs/inode.c:2177
       ext4_write_checks fs/ext4/file.c:264 [inline]
       ext4_buffered_write_iter+0x12c/0x294 fs/ext4/file.c:280
       ext4_file_write_iter+0x84/0x408 fs/ext4/file.c:700
       call_write_iter include/linux/fs.h:2199 [inline]
       new_sync_write fs/read_write.c:491 [inline]
       vfs_write+0x2dc/0x46c fs/read_write.c:584
       ksys_write+0xb4/0x160 fs/read_write.c:637
       __do_sys_write fs/read_write.c:649 [inline]
       __se_sys_write fs/read_write.c:646 [inline]
       __arm64_sys_write+0x24/0x34 fs/read_write.c:646
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall arch/arm64/kernel/syscall.c:52 [inline]
       el0_svc_common+0x138/0x220 arch/arm64/kernel/syscall.c:142
       do_el0_svc+0x48/0x140 arch/arm64/kernel/syscall.c:197
       el0_svc+0x58/0x150 arch/arm64/kernel/entry-common.c:637
       el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
       el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:584

-> #0 (&sb->s_type->i_mutex_key#8){++++}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3097 [inline]
       check_prevs_add kernel/locking/lockdep.c:3216 [inline]
       validate_chain kernel/locking/lockdep.c:3831 [inline]
       __lock_acquire+0x1530/0x3084 kernel/locking/lockdep.c:5055
       lock_acquire+0x100/0x1f8 kernel/locking/lockdep.c:5668
       down_write+0x5c/0x88 kernel/locking/rwsem.c:1562
       inode_lock include/linux/fs.h:756 [inline]
       ext4_xattr_inode_create fs/ext4/xattr.c:1453 [inline]
       ext4_xattr_inode_lookup_create fs/ext4/xattr.c:1536 [inline]
       ext4_xattr_set_entry+0xdbc/0xe00 fs/ext4/xattr.c:1664
       ext4_xattr_ibody_set+0x94/0x184 fs/ext4/xattr.c:2224
       ext4_xattr_set_handle+0x648/0x9a0 fs/ext4/xattr.c:2381
       ext4_xattr_set+0x100/0x1d0 fs/ext4/xattr.c:2495
       ext4_xattr_trusted_set+0x4c/0x64 fs/ext4/xattr_trusted.c:38
       __vfs_setxattr+0x250/0x260 fs/xattr.c:182
       __vfs_setxattr_noperm+0xcc/0x320 fs/xattr.c:216
       __vfs_setxattr_locked+0x16c/0x194 fs/xattr.c:277
       vfs_setxattr+0xf4/0x1f4 fs/xattr.c:309
       do_setxattr fs/xattr.c:594 [inline]
       setxattr fs/xattr.c:617 [inline]
       path_setxattr+0x354/0x414 fs/xattr.c:636
       __do_sys_lsetxattr fs/xattr.c:659 [inline]
       __se_sys_lsetxattr fs/xattr.c:655 [inline]
       __arm64_sys_lsetxattr+0x2c/0x40 fs/xattr.c:655
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall arch/arm64/kernel/syscall.c:52 [inline]
       el0_svc_common+0x138/0x220 arch/arm64/kernel/syscall.c:142
       do_el0_svc+0x48/0x140 arch/arm64/kernel/syscall.c:197
       el0_svc+0x58/0x150 arch/arm64/kernel/entry-common.c:637
       el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
       el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:584

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&ei->xattr_sem);
                               lock(&sb->s_type->i_mutex_key#8);
                               lock(&ei->xattr_sem);
  lock(&sb->s_type->i_mutex_key#8);

 *** DEADLOCK ***

3 locks held by syz-executor.0/3668:
 #0: ffff0000c9dee460 (sb_writers#3){.+.+}-{0:0}, at: mnt_want_write+0x20/0x64 fs/namespace.c:393
 #1: ffff0000cf16b3d0 (&type->i_mutex_dir_key#3){++++}-{3:3}, at: inode_lock include/linux/fs.h:756 [inline]
 #1: ffff0000cf16b3d0 (&type->i_mutex_dir_key#3){++++}-{3:3}, at: vfs_setxattr+0xd4/0x1f4 fs/xattr.c:308
 #2: ffff0000cf16b098 (&ei->xattr_sem){++++}-{3:3}, at: ext4_write_lock_xattr fs/ext4/xattr.h:155 [inline]
 #2: ffff0000cf16b098 (&ei->xattr_sem){++++}-{3:3}, at: ext4_xattr_set_handle+0xd0/0x9a0 fs/ext4/xattr.c:2308

stack backtrace:
CPU: 1 PID: 3668 Comm: syz-executor.0 Not tainted 6.1.0-rc8-syzkaller-00172-ga5541c0811a0-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
Call trace:
 dump_backtrace+0x1c4/0x1f0 arch/arm64/kernel/stacktrace.c:156
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:163
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x104/0x16c lib/dump_stack.c:106
 dump_stack+0x1c/0x58 lib/dump_stack.c:113
 print_circular_bug+0x2c4/0x2c8 kernel/locking/lockdep.c:2055
 check_noncircular+0x14c/0x154 kernel/locking/lockdep.c:2177
 check_prev_add kernel/locking/lockdep.c:3097 [inline]
 check_prevs_add kernel/locking/lockdep.c:3216 [inline]
 validate_chain kernel/locking/lockdep.c:3831 [inline]
 __lock_acquire+0x1530/0x3084 kernel/locking/lockdep.c:5055
 lock_acquire+0x100/0x1f8 kernel/locking/lockdep.c:5668
 down_write+0x5c/0x88 kernel/locking/rwsem.c:1562
 inode_lock include/linux/fs.h:756 [inline]
 ext4_xattr_inode_create fs/ext4/xattr.c:1453 [inline]
 ext4_xattr_inode_lookup_create fs/ext4/xattr.c:1536 [inline]
 ext4_xattr_set_entry+0xdbc/0xe00 fs/ext4/xattr.c:1664
 ext4_xattr_ibody_set+0x94/0x184 fs/ext4/xattr.c:2224
 ext4_xattr_set_handle+0x648/0x9a0 fs/ext4/xattr.c:2381
 ext4_xattr_set+0x100/0x1d0 fs/ext4/xattr.c:2495
 ext4_xattr_trusted_set+0x4c/0x64 fs/ext4/xattr_trusted.c:38
 __vfs_setxattr+0x250/0x260 fs/xattr.c:182
 __vfs_setxattr_noperm+0xcc/0x320 fs/xattr.c:216
 __vfs_setxattr_locked+0x16c/0x194 fs/xattr.c:277
 vfs_setxattr+0xf4/0x1f4 fs/xattr.c:309
 do_setxattr fs/xattr.c:594 [inline]
 setxattr fs/xattr.c:617 [inline]
 path_setxattr+0x354/0x414 fs/xattr.c:636
 __do_sys_lsetxattr fs/xattr.c:659 [inline]
 __se_sys_lsetxattr fs/xattr.c:655 [inline]
 __arm64_sys_lsetxattr+0x2c/0x40 fs/xattr.c:655
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall arch/arm64/kernel/syscall.c:52 [inline]
 el0_svc_common+0x138/0x220 arch/arm64/kernel/syscall.c:142
 do_el0_svc+0x48/0x140 arch/arm64/kernel/syscall.c:197
 el0_svc+0x58/0x150 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:584


Tested on:

commit:         a5541c08 Merge branch 'for-next/core' into for-kernelci
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=16f5d4bc480000
kernel config:  https://syzkaller.appspot.com/x/.config?x=cbd4e584773e9397
dashboard link: https://syzkaller.appspot.com/bug?extid=d3bb749184481f92deb5
compiler:       Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
userspace arch: arm64
patch:          https://syzkaller.appspot.com/x/patch.diff?x=15be6de4480000


       reply	other threads:[~2022-12-29  1:24 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20221229005540.2777-1-hdanton@sina.com>
2022-12-29  1:23 ` syzbot [this message]
     [not found] <20221229093654.2868-1-hdanton@sina.com>
2022-12-29  9:52 ` [syzbot] [ext4?] possible deadlock in ext4_find_inline_entry syzbot
     [not found] <20221228093841.2684-1-hdanton@sina.com>
2022-12-28  9:50 ` syzbot
2022-12-28  7:59 syzbot

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