[syzbot] [keyrings?] [lsm?] [ext4?] possible deadlock in keyring_clear (2)

syzbot syzbot+1b2d1134e0b675176a15 at syzkaller.appspotmail.com
Sun Sep 22 11:43:03 UTC 2024 

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-08481-g88264981f208-dirty #0 Not tainted
------------------------------------------------------
kswapd0/79 is trying to acquire lock:
ffff888000b01258 (&type->lock_class){+.+.}-{3:3}, at: keyring_clear+0xb2/0x350 security/keys/keyring.c:1655

but task is already holding lock:
ffffffff8ea36740 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:6844 [inline]
ffffffff8ea36740 (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_in_empty_tree lib/assoc_array.c:457 [inline]
       assoc_array_insert+0x52c/0x33e0 lib/assoc_array.c:991
       __key_link_begin+0xe5/0x1f0 security/keys/keyring.c:1314
       __key_create_or_update+0x570/0xc70 security/keys/key.c:874
       key_create_or_update+0x42/0x60 security/keys/key.c:1018
       x509_load_certificate_list+0x149/0x270 crypto/asymmetric_keys/x509_loader.c:31
       do_one_initcall+0x248/0x880 init/main.c:1269
       do_initcall_level+0x157/0x210 init/main.c:1331
       do_initcalls+0x3f/0x80 init/main.c:1347
       kernel_init_freeable+0x435/0x5d0 init/main.c:1580
       kernel_init+0x1d/0x2b0 init/main.c:1469
       ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

-> #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:731
       __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 kswapd0/79:
 #0: ffffffff8ea36740 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:6844 [inline]
 #0: ffffffff8ea36740 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0xbf1/0x3700 mm/vmscan.c:7226
 #1: ffff888035f440e0 (&type->s_umount_key#32){++++}-{3:3}, at: super_trylock_shared fs/super.c:562 [inline]
 #1: ffff888035f440e0 (&type->s_umount_key#32){++++}-{3:3}, at: super_cache_scan+0x94/0x4b0 fs/super.c:196

stack backtrace:
CPU: 0 UID: 0 PID: 79 Comm: kswapd0 Not tainted 6.11.0-syzkaller-08481-g88264981f208-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:731
 __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:         88264981 Merge tag 'sched_ext-for-6.12' of git://git.k..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14ee4e07980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=e851828834875d6f
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=174eec27980000

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