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Message-ID: <69484ed3.a70a0220.25eec0.0077.GAE@google.com>
Date: Sun, 21 Dec 2025 11:47:31 -0800
From: syzbot <syzbot+f55b043dacf43776b50c@...kaller.appspotmail.com>
To: dhowells@...hat.com, jarkko@...nel.org, jmorris@...ei.org,
keyrings@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-security-module@...r.kernel.org, paul@...l-moore.com, serge@...lyn.com,
syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [keyrings?] [lsm?] possible deadlock in keyring_clear (3)
syzbot has found a reproducer for the following issue on:
HEAD commit: 9094662f6707 Merge tag 'ata-6.19-rc2' of git://git.kernel...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1022f77c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=513255d80ab78f2b
dashboard link: https://syzkaller.appspot.com/bug?extid=f55b043dacf43776b50c
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=168a8b1a580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16c06b1a580000
Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-9094662f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/baa55f8cf722/vmlinux-9094662f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/aaaa8a404a70/bzImage-9094662f.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/7a86e58a207c/mount_2.gz
fsck result: OK (log: https://syzkaller.appspot.com/x/fsck.log?x=12c06b1a580000)
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f55b043dacf43776b50c@...kaller.appspotmail.com
======================================================
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>
---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.
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