Kernel bug: possible deadlock in keyring_clear (3)
Subsystem: keyrings, lsm
Status: open

Crash report:
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
kswapd1/79 is trying to acquire lock:
ffff8880433bfcd8 (&type->lock_class){+.+.}-{4:4}, at: keyring_clear+0xaf/0x240 security/keys/keyring.c:1658

but task is already holding lock:
ffffffff8e051820 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:6975 [inline]
ffffffff8e051820 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0x92a/0x2820 mm/vmscan.c:7354

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (fs_reclaim){+.+.}-{0:0}:
       __fs_reclaim_acquire mm/page_alloc.c:4301 [inline]
       fs_reclaim_acquire+0x72/0x100 mm/page_alloc.c:4315
       might_alloc include/linux/sched/mm.h:317 [inline]
       slab_pre_alloc_hook mm/slub.c:4904 [inline]
       slab_alloc_node mm/slub.c:5239 [inline]
       __kmalloc_cache_noprof+0x40/0x700 mm/slub.c:5771
       kmalloc_noprof include/linux/slab.h:957 [inline]
       kzalloc_noprof include/linux/slab.h:1094 [inline]
       assoc_array_insert+0x92/0x2f90 lib/assoc_array.c:980
       __key_link_begin+0xd6/0x1f0 security/keys/keyring.c:1317
       __key_create_or_update+0x41a/0xa30 security/keys/key.c:877
       key_create_or_update+0x42/0x60 security/keys/key.c:1021
       x509_load_certificate_list+0x145/0x280 crypto/asymmetric_keys/x509_loader.c:31
       do_one_initcall+0x1f1/0x800 init/main.c:1378
       do_initcall_level+0x104/0x190 init/main.c:1440
       do_initcalls+0x59/0xa0 init/main.c:1456
       kernel_init_freeable+0x2a7/0x3d0 init/main.c:1688
       kernel_init+0x1d/0x1d0 init/main.c:1578
       ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

-> #0 (&type->lock_class){+.+.}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3165 [inline]
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x15a6/0x2cf0 kernel/locking/lockdep.c:5237
       lock_acquire+0x107/0x340 kernel/locking/lockdep.c:5868
       down_write+0x96/0x1f0 kernel/locking/rwsem.c:1590
       keyring_clear+0xaf/0x240 security/keys/keyring.c:1658
       fscrypt_put_master_key+0xca/0x190 fs/crypto/keyring.c:80
       put_crypt_info+0x26d/0x310 fs/crypto/keysetup.c:573
       fscrypt_put_encryption_info+0xf6/0x140 fs/crypto/keysetup.c:787
       ext4_clear_inode+0x170/0x2f0 fs/ext4/super.c:1529
       ext4_evict_inode+0x9f6/0xe60 fs/ext4/inode.c:320
       evict+0x5f4/0xae0 fs/inode.c:837
       __dentry_kill+0x209/0x660 fs/dcache.c:670
       shrink_kill+0xa9/0x2c0 fs/dcache.c:1137
       shrink_dentry_list+0x2e0/0x5e0 fs/dcache.c:1164
       prune_dcache_sb+0x10e/0x180 fs/dcache.c:1246
       super_cache_scan+0x369/0x4b0 fs/super.c:222
       do_shrink_slab+0x6df/0x10d0 mm/shrinker.c:437
       shrink_slab_memcg mm/shrinker.c:550 [inline]
       shrink_slab+0x7ef/0x10d0 mm/shrinker.c:628
       shrink_one+0x2d9/0x720 mm/vmscan.c:4921
       shrink_many mm/vmscan.c:4982 [inline]
       lru_gen_shrink_node mm/vmscan.c:5060 [inline]
       shrink_node+0x2f7d/0x35b0 mm/vmscan.c:6047
       kswapd_shrink_node mm/vmscan.c:6901 [inline]
       balance_pgdat mm/vmscan.c:7084 [inline]
       kswapd+0x145a/0x2820 mm/vmscan.c:7354
       kthread+0x711/0x8a0 kernel/kthread.c:463
       ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

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 kswapd1/79:
 #0: ffffffff8e051820 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:6975 [inline]
 #0: ffffffff8e051820 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0x92a/0x2820 mm/vmscan.c:7354
 #1: ffff88803fa5a0e0 (&type->s_umount_key#32){++++}-{4:4}, at: super_trylock_shared fs/super.c:563 [inline]
 #1: ffff88803fa5a0e0 (&type->s_umount_key#32){++++}-{4:4}, at: super_cache_scan+0x91/0x4b0 fs/super.c:197

stack backtrace:
CPU: 0 UID: 0 PID: 79 Comm: kswapd1 Not tainted syzkaller #0 PREEMPT(full) 
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_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_circular_bug+0x2e2/0x300 kernel/locking/lockdep.c:2043
 check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2175
 check_prev_add kernel/locking/lockdep.c:3165 [inline]
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain kernel/locking/lockdep.c:3908 [inline]
 __lock_acquire+0x15a6/0x2cf0 kernel/locking/lockdep.c:5237
 lock_acquire+0x107/0x340 kernel/locking/lockdep.c:5868
 down_write+0x96/0x1f0 kernel/locking/rwsem.c:1590
 keyring_clear+0xaf/0x240 security/keys/keyring.c:1658
 fscrypt_put_master_key+0xca/0x190 fs/crypto/keyring.c:80
 put_crypt_info+0x26d/0x310 fs/crypto/keysetup.c:573
 fscrypt_put_encryption_info+0xf6/0x140 fs/crypto/keysetup.c:787
 ext4_clear_inode+0x170/0x2f0 fs/ext4/super.c:1529
 ext4_evict_inode+0x9f6/0xe60 fs/ext4/inode.c:320
 evict+0x5f4/0xae0 fs/inode.c:837
 __dentry_kill+0x209/0x660 fs/dcache.c:670
 shrink_kill+0xa9/0x2c0 fs/dcache.c:1137
 shrink_dentry_list+0x2e0/0x5e0 fs/dcache.c:1164
 prune_dcache_sb+0x10e/0x180 fs/dcache.c:1246
 super_cache_scan+0x369/0x4b0 fs/super.c:222
 do_shrink_slab+0x6df/0x10d0 mm/shrinker.c:437
 shrink_slab_memcg mm/shrinker.c:550 [inline]
 shrink_slab+0x7ef/0x10d0 mm/shrinker.c:628
 shrink_one+0x2d9/0x720 mm/vmscan.c:4921
 shrink_many mm/vmscan.c:4982 [inline]
 lru_gen_shrink_node mm/vmscan.c:5060 [inline]
 shrink_node+0x2f7d/0x35b0 mm/vmscan.c:6047
 kswapd_shrink_node mm/vmscan.c:6901 [inline]
 balance_pgdat mm/vmscan.c:7084 [inline]
 kswapd+0x145a/0x2820 mm/vmscan.c:7354
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>