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Message-ID: <66f67deb.050a0220.46d20.0015.GAE@google.com>
Date: Fri, 27 Sep 2024 02:42:03 -0700
From: syzbot <syzbot+1b2d1134e0b675176a15@...kaller.appspotmail.com>
To: linux-kernel@...r.kernel.org, lizhi.xu@...driver.com, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [keyrings?] [lsm?] [ext4?] possible deadlock in
 keyring_clear (2)

Hello,

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

======================================================
WARNING: possible circular locking dependency detected
6.11.0-syzkaller-11558-g075dbe9f6e3c-dirty #0 Not tainted
------------------------------------------------------
kswapd0/73 is trying to acquire lock:
ffff88803d6355d8 (&type->lock_class){+.+.}-{3:3}, at: keyring_clear+0xb2/0x350 security/keys/keyring.c:1655

but task is already holding lock:
ffffffff8ea37100 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:6844 [inline]
ffffffff8ea37100 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0xbf1/0x3700 mm/vmscan.c:7226

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (fs_reclaim){+.+.}-{0:0}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5822
       __fs_reclaim_acquire mm/page_alloc.c:3834 [inline]
       fs_reclaim_acquire+0x88/0x140 mm/page_alloc.c:3848
       might_alloc include/linux/sched/mm.h:327 [inline]
       slab_pre_alloc_hook mm/slub.c:4037 [inline]
       slab_alloc_node mm/slub.c:4115 [inline]
       __kmalloc_cache_noprof+0x3d/0x2c0 mm/slub.c:4291
       kmalloc_noprof include/linux/slab.h:878 [inline]
       kzalloc_noprof include/linux/slab.h:1014 [inline]
       assoc_array_insert+0xfe/0x33e0 lib/assoc_array.c:980
       __key_link_begin+0xe5/0x1f0 security/keys/keyring.c:1314
       key_instantiate_and_link+0x2a0/0x510 security/keys/key.c:525
       add_master_key_user+0x222/0x2e0 fs/crypto/keyring.c:400
       add_new_master_key+0x2f8/0x5d0 fs/crypto/keyring.c:451
       do_add_master_key fs/crypto/keyring.c:529 [inline]
       add_master_key+0x419/0x970 fs/crypto/keyring.c:579
       fscrypt_ioctl_add_key+0x3e9/0x590 fs/crypto/keyring.c:752
       __ext4_ioctl fs/ext4/ioctl.c:1537 [inline]
       ext4_ioctl+0x18b1/0x5590 fs/ext4/ioctl.c:1626
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:907 [inline]
       __se_sys_ioctl+0xf9/0x170 fs/ioctl.c:893
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&type->lock_class){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3158 [inline]
       check_prevs_add kernel/locking/lockdep.c:3277 [inline]
       validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3901
       __lock_acquire+0x1384/0x2050 kernel/locking/lockdep.c:5199
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5822
       down_write+0x99/0x220 kernel/locking/rwsem.c:1579
       keyring_clear+0xb2/0x350 security/keys/keyring.c:1655
       fscrypt_put_master_key+0xc8/0x190 fs/crypto/keyring.c:79
       put_crypt_info+0x275/0x320 fs/crypto/keysetup.c:548
       fscrypt_put_encryption_info+0x40/0x60 fs/crypto/keysetup.c:753
       ext4_clear_inode+0x15b/0x1c0 fs/ext4/super.c:1525
       ext4_evict_inode+0xabc/0xf50 fs/ext4/inode.c:323
       evict+0x4e8/0x9b0 fs/inode.c:723
       __dentry_kill+0x20d/0x630 fs/dcache.c:615
       shrink_kill+0xa9/0x2c0 fs/dcache.c:1060
       shrink_dentry_list+0x2c0/0x5b0 fs/dcache.c:1087
       prune_dcache_sb+0x10f/0x180 fs/dcache.c:1168
       super_cache_scan+0x34f/0x4b0 fs/super.c:221
       do_shrink_slab+0x701/0x1160 mm/shrinker.c:435
       shrink_slab_memcg mm/shrinker.c:548 [inline]
       shrink_slab+0x878/0x14d0 mm/shrinker.c:626
       shrink_one+0x43b/0x850 mm/vmscan.c:4818
       shrink_many mm/vmscan.c:4879 [inline]
       lru_gen_shrink_node mm/vmscan.c:4957 [inline]
       shrink_node+0x3799/0x3de0 mm/vmscan.c:5937
       kswapd_shrink_node mm/vmscan.c:6765 [inline]
       balance_pgdat mm/vmscan.c:6957 [inline]
       kswapd+0x1ca3/0x3700 mm/vmscan.c:7226
       kthread+0x2f0/0x390 kernel/kthread.c:389
       ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(fs_reclaim);
                               lock(&type->lock_class);
                               lock(fs_reclaim);
  lock(&type->lock_class);

 *** DEADLOCK ***

2 locks held by kswapd0/73:
 #0: ffffffff8ea37100 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:6844 [inline]
 #0: ffffffff8ea37100 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0xbf1/0x3700 mm/vmscan.c:7226
 #1: ffff888039c6c0e0 (&type->s_umount_key#32){++++}-{3:3}, at: super_trylock_shared fs/super.c:562 [inline]
 #1: ffff888039c6c0e0 (&type->s_umount_key#32){++++}-{3:3}, at: super_cache_scan+0x94/0x4b0 fs/super.c:196

stack backtrace:
CPU: 0 UID: 0 PID: 73 Comm: kswapd0 Not tainted 6.11.0-syzkaller-11558-g075dbe9f6e3c-dirty #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_circular_bug+0x13a/0x1b0 kernel/locking/lockdep.c:2074
 check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2203
 check_prev_add kernel/locking/lockdep.c:3158 [inline]
 check_prevs_add kernel/locking/lockdep.c:3277 [inline]
 validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3901
 __lock_acquire+0x1384/0x2050 kernel/locking/lockdep.c:5199
 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5822
 down_write+0x99/0x220 kernel/locking/rwsem.c:1579
 keyring_clear+0xb2/0x350 security/keys/keyring.c:1655
 fscrypt_put_master_key+0xc8/0x190 fs/crypto/keyring.c:79
 put_crypt_info+0x275/0x320 fs/crypto/keysetup.c:548
 fscrypt_put_encryption_info+0x40/0x60 fs/crypto/keysetup.c:753
 ext4_clear_inode+0x15b/0x1c0 fs/ext4/super.c:1525
 ext4_evict_inode+0xabc/0xf50 fs/ext4/inode.c:323
 evict+0x4e8/0x9b0 fs/inode.c:723
 __dentry_kill+0x20d/0x630 fs/dcache.c:615
 shrink_kill+0xa9/0x2c0 fs/dcache.c:1060
 shrink_dentry_list+0x2c0/0x5b0 fs/dcache.c:1087
 prune_dcache_sb+0x10f/0x180 fs/dcache.c:1168
 super_cache_scan+0x34f/0x4b0 fs/super.c:221
 do_shrink_slab+0x701/0x1160 mm/shrinker.c:435
 shrink_slab_memcg mm/shrinker.c:548 [inline]
 shrink_slab+0x878/0x14d0 mm/shrinker.c:626
 shrink_one+0x43b/0x850 mm/vmscan.c:4818
 shrink_many mm/vmscan.c:4879 [inline]
 lru_gen_shrink_node mm/vmscan.c:4957 [inline]
 shrink_node+0x3799/0x3de0 mm/vmscan.c:5937
 kswapd_shrink_node mm/vmscan.c:6765 [inline]
 balance_pgdat mm/vmscan.c:6957 [inline]
 kswapd+0x1ca3/0x3700 mm/vmscan.c:7226
 kthread+0x2f0/0x390 kernel/kthread.c:389
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>


Tested on:

commit:         075dbe9f Merge tag 'soc-ep93xx-dt-6.12' of git://git.k..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12b4c507980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f6cf7b6189844756
dashboard link: https://syzkaller.appspot.com/bug?extid=1b2d1134e0b675176a15
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=1545159f980000

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