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Peter ZijlstraJulia Cartwright
Peter Zijlstra
authored and
Julia Cartwright
committed
crypto: Convert crypto notifier chain to SRCU
The crypto notifier deadlocks on RT. Though this can be a real deadlock on mainline as well due to fifo fair rwsems. The involved parties here are: [ 82.172678] swapper/0 S 0000000000000001 0 1 0 0x00000000 [ 82.172682] ffff88042f18fcf0 0000000000000046 ffff88042f18fc80 ffffffff81491238 [ 82.172685] 0000000000011cc0 0000000000011cc0 ffff88042f18c040 ffff88042f18ffd8 [ 82.172688] 0000000000011cc0 0000000000011cc0 ffff88042f18ffd8 0000000000011cc0 [ 82.172689] Call Trace: [ 82.172697] [<ffffffff81491238>] ? _raw_spin_unlock_irqrestore+0x6c/0x7a [ 82.172701] [<ffffffff8148fd3f>] schedule+0x64/0x66 [ 82.172704] [<ffffffff8148ec6b>] schedule_timeout+0x27/0xd0 [ 82.172708] [<ffffffff81043c0c>] ? unpin_current_cpu+0x1a/0x6c [ 82.172713] [<ffffffff8106e491>] ? migrate_enable+0x12f/0x141 [ 82.172716] [<ffffffff8148fbbd>] wait_for_common+0xbb/0x11f [ 82.172719] [<ffffffff810709f2>] ? try_to_wake_up+0x182/0x182 [ 82.172722] [<ffffffff8148fc96>] wait_for_completion_interruptible+0x1d/0x2e [ 82.172726] [<ffffffff811debfd>] crypto_wait_for_test+0x49/0x6b [ 82.172728] [<ffffffff811ded32>] crypto_register_alg+0x53/0x5a [ 82.172730] [<ffffffff811ded6c>] crypto_register_algs+0x33/0x72 [ 82.172734] [<ffffffff81ad7686>] ? aes_init+0x12/0x12 [ 82.172737] [<ffffffff81ad76ea>] aesni_init+0x64/0x66 [ 82.172741] [<ffffffff81000318>] do_one_initcall+0x7f/0x13b [ 82.172744] [<ffffffff81ac4d34>] kernel_init+0x199/0x22c [ 82.172747] [<ffffffff81ac44ef>] ? loglevel+0x31/0x31 [ 82.172752] [<ffffffff814987c4>] kernel_thread_helper+0x4/0x10 [ 82.172755] [<ffffffff81491574>] ? retint_restore_args+0x13/0x13 [ 82.172759] [<ffffffff81ac4b9b>] ? start_kernel+0x3ca/0x3ca [ 82.172761] [<ffffffff814987c0>] ? gs_change+0x13/0x13 [ 82.174186] cryptomgr_test S 0000000000000001 0 41 2 0x00000000 [ 82.174189] ffff88042c971980 0000000000000046 ffffffff81d74830 0000000000000292 [ 82.174192] 0000000000011cc0 0000000000011cc0 ffff88042c96eb80 ffff88042c971fd8 [ 82.174195] 0000000000011cc0 0000000000011cc0 ffff88042c971fd8 0000000000011cc0 [ 82.174195] Call Trace: [ 82.174198] [<ffffffff8148fd3f>] schedule+0x64/0x66 [ 82.174201] [<ffffffff8148ec6b>] schedule_timeout+0x27/0xd0 [ 82.174204] [<ffffffff81043c0c>] ? unpin_current_cpu+0x1a/0x6c [ 82.174206] [<ffffffff8106e491>] ? migrate_enable+0x12f/0x141 [ 82.174209] [<ffffffff8148fbbd>] wait_for_common+0xbb/0x11f [ 82.174212] [<ffffffff810709f2>] ? try_to_wake_up+0x182/0x182 [ 82.174215] [<ffffffff8148fc96>] wait_for_completion_interruptible+0x1d/0x2e [ 82.174218] [<ffffffff811e4883>] cryptomgr_notify+0x280/0x385 [ 82.174221] [<ffffffff814943de>] notifier_call_chain+0x6b/0x98 [ 82.174224] [<ffffffff8108a11c>] ? rt_down_read+0x10/0x12 [ 82.174227] [<ffffffff810677cd>] __blocking_notifier_call_chain+0x70/0x8d [ 82.174230] [<ffffffff810677fe>] blocking_notifier_call_chain+0x14/0x16 [ 82.174234] [<ffffffff811dd272>] crypto_probing_notify+0x24/0x50 [ 82.174236] [<ffffffff811dd7a1>] crypto_alg_mod_lookup+0x3e/0x74 [ 82.174238] [<ffffffff811dd949>] crypto_alloc_base+0x36/0x8f [ 82.174241] [<ffffffff811e9408>] cryptd_alloc_ablkcipher+0x6e/0xb5 [ 82.174243] [<ffffffff811dd591>] ? kzalloc.clone.5+0xe/0x10 [ 82.174246] [<ffffffff8103085d>] ablk_init_common+0x1d/0x38 [ 82.174249] [<ffffffff8103852a>] ablk_ecb_init+0x15/0x17 [ 82.174251] [<ffffffff811dd8c6>] __crypto_alloc_tfm+0xc7/0x114 [ 82.174254] [<ffffffff811e0caa>] ? crypto_lookup_skcipher+0x1f/0xe4 [ 82.174256] [<ffffffff811e0dcf>] crypto_alloc_ablkcipher+0x60/0xa5 [ 82.174258] [<ffffffff811e5bde>] alg_test_skcipher+0x24/0x9b [ 82.174261] [<ffffffff8106d96d>] ? finish_task_switch+0x3f/0xfa [ 82.174263] [<ffffffff811e6b8e>] alg_test+0x16f/0x1d7 [ 82.174267] [<ffffffff811e45ac>] ? cryptomgr_probe+0xac/0xac [ 82.174269] [<ffffffff811e45d8>] cryptomgr_test+0x2c/0x47 [ 82.174272] [<ffffffff81061161>] kthread+0x7e/0x86 [ 82.174275] [<ffffffff8106d9dd>] ? finish_task_switch+0xaf/0xfa [ 82.174278] [<ffffffff814987c4>] kernel_thread_helper+0x4/0x10 [ 82.174281] [<ffffffff81491574>] ? retint_restore_args+0x13/0x13 [ 82.174284] [<ffffffff810610e3>] ? __init_kthread_worker+0x8c/0x8c [ 82.174287] [<ffffffff814987c0>] ? gs_change+0x13/0x13 [ 82.174329] cryptomgr_probe D 0000000000000002 0 47 2 0x00000000 [ 82.174332] ffff88042c991b70 0000000000000046 ffff88042c991bb0 0000000000000006 [ 82.174335] 0000000000011cc0 0000000000011cc0 ffff88042c98ed00 ffff88042c991fd8 [ 82.174338] 0000000000011cc0 0000000000011cc0 ffff88042c991fd8 0000000000011cc0 [ 82.174338] Call Trace: [ 82.174342] [<ffffffff8148fd3f>] schedule+0x64/0x66 [ 82.174344] [<ffffffff814901ad>] __rt_mutex_slowlock+0x85/0xbe [ 82.174347] [<ffffffff814902d2>] rt_mutex_slowlock+0xec/0x159 [ 82.174351] [<ffffffff81089c4d>] rt_mutex_fastlock.clone.8+0x29/0x2f [ 82.174353] [<ffffffff81490372>] rt_mutex_lock+0x33/0x37 [ 82.174356] [<ffffffff8108a0f2>] __rt_down_read+0x50/0x5a [ 82.174358] [<ffffffff8108a11c>] ? rt_down_read+0x10/0x12 [ 82.174360] [<ffffffff8108a11c>] rt_down_read+0x10/0x12 [ 82.174363] [<ffffffff810677b5>] __blocking_notifier_call_chain+0x58/0x8d [ 82.174366] [<ffffffff810677fe>] blocking_notifier_call_chain+0x14/0x16 [ 82.174369] [<ffffffff811dd272>] crypto_probing_notify+0x24/0x50 [ 82.174372] [<ffffffff811debd6>] crypto_wait_for_test+0x22/0x6b [ 82.174374] [<ffffffff811decd3>] crypto_register_instance+0xb4/0xc0 [ 82.174377] [<ffffffff811e9b76>] cryptd_create+0x378/0x3b6 [ 82.174379] [<ffffffff811de512>] ? __crypto_lookup_template+0x5b/0x63 [ 82.174382] [<ffffffff811e4545>] cryptomgr_probe+0x45/0xac [ 82.174385] [<ffffffff811e4500>] ? crypto_alloc_pcomp+0x1b/0x1b [ 82.174388] [<ffffffff81061161>] kthread+0x7e/0x86 [ 82.174391] [<ffffffff8106d9dd>] ? finish_task_switch+0xaf/0xfa [ 82.174394] [<ffffffff814987c4>] kernel_thread_helper+0x4/0x10 [ 82.174398] [<ffffffff81491574>] ? retint_restore_args+0x13/0x13 [ 82.174401] [<ffffffff810610e3>] ? __init_kthread_worker+0x8c/0x8c [ 82.174403] [<ffffffff814987c0>] ? gs_change+0x13/0x13 cryptomgr_test spawns the cryptomgr_probe thread from the notifier call. The probe thread fires the same notifier as the test thread and deadlocks on the rwsem on RT. Now this is a potential deadlock in mainline as well, because we have fifo fair rwsems. If another thread blocks with a down_write() on the notifier chain before the probe thread issues the down_read() it will block the probe thread and the whole party is dead locked. Signed-off-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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-7
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3 files changed

+7
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lines changed

‎crypto/algapi.c

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -731,13 +731,13 @@ EXPORT_SYMBOL_GPL(crypto_spawn_tfm2);
731731

732732
int crypto_register_notifier(struct notifier_block *nb)
733733
{
734-
return blocking_notifier_chain_register(&crypto_chain, nb);
734+
return srcu_notifier_chain_register(&crypto_chain, nb);
735735
}
736736
EXPORT_SYMBOL_GPL(crypto_register_notifier);
737737

738738
int crypto_unregister_notifier(struct notifier_block *nb)
739739
{
740-
return blocking_notifier_chain_unregister(&crypto_chain, nb);
740+
return srcu_notifier_chain_unregister(&crypto_chain, nb);
741741
}
742742
EXPORT_SYMBOL_GPL(crypto_unregister_notifier);
743743

‎crypto/api.c

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -31,7 +31,7 @@ EXPORT_SYMBOL_GPL(crypto_alg_list);
3131
DECLARE_RWSEM(crypto_alg_sem);
3232
EXPORT_SYMBOL_GPL(crypto_alg_sem);
3333

34-
BLOCKING_NOTIFIER_HEAD(crypto_chain);
34+
SRCU_NOTIFIER_HEAD(crypto_chain);
3535
EXPORT_SYMBOL_GPL(crypto_chain);
3636

3737
static struct crypto_alg *crypto_larval_wait(struct crypto_alg *alg);
@@ -236,10 +236,10 @@ int crypto_probing_notify(unsigned long val, void *v)
236236
{
237237
int ok;
238238

239-
ok = blocking_notifier_call_chain(&crypto_chain, val, v);
239+
ok = srcu_notifier_call_chain(&crypto_chain, val, v);
240240
if (ok == NOTIFY_DONE) {
241241
request_module("cryptomgr");
242-
ok = blocking_notifier_call_chain(&crypto_chain, val, v);
242+
ok = srcu_notifier_call_chain(&crypto_chain, val, v);
243243
}
244244

245245
return ok;

‎crypto/internal.h

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -47,7 +47,7 @@ struct crypto_larval {
4747

4848
extern struct list_head crypto_alg_list;
4949
extern struct rw_semaphore crypto_alg_sem;
50-
extern struct blocking_notifier_head crypto_chain;
50+
extern struct srcu_notifier_head crypto_chain;
5151

5252
#ifdef CONFIG_PROC_FS
5353
void __init crypto_init_proc(void);
@@ -146,7 +146,7 @@ static inline int crypto_is_moribund(struct crypto_alg *alg)
146146

147147
static inline void crypto_notify(unsigned long val, void *v)
148148
{
149-
blocking_notifier_call_chain(&crypto_chain, val, v);
149+
srcu_notifier_call_chain(&crypto_chain, val, v);
150150
}
151151

152152
#endif /* _CRYPTO_INTERNAL_H */

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