f2b639b2aa
[ Upstream commit3906f64022] The crypto notify call occurs with a read mutex held so you must not do any substantial work directly. In particular, you cannot call crypto_alloc_* as they may trigger further notifications which may dead-lock in the presence of another writer. This patch fixes this by postponing the work into a work queue and taking the same lock in the module init function. While we're at it this patch also ensures that all RCU accesses are marked appropriately (tested with sparse). Finally this also reveals a race condition in module param show function as it may be called prior to the module init function. It's fixed by testing whether crct10dif_tfm is NULL (this is true iff the init function has not completed assuming fallback is false). Fixes:11dcb1037f("crc-t10dif: Allow current transform to be...") Fixes:b76377543b("crc-t10dif: Pick better transform if one...") Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> Reviewed-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: Sasha Levin <sashal@kernel.org>
132 lines
3.2 KiB
C
132 lines
3.2 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* T10 Data Integrity Field CRC16 calculation
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*
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* Copyright (c) 2007 Oracle Corporation. All rights reserved.
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* Written by Martin K. Petersen <martin.petersen@oracle.com>
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*/
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#include <linux/types.h>
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#include <linux/module.h>
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#include <linux/crc-t10dif.h>
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#include <linux/err.h>
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#include <linux/init.h>
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#include <crypto/hash.h>
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#include <crypto/algapi.h>
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#include <linux/static_key.h>
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#include <linux/notifier.h>
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static struct crypto_shash __rcu *crct10dif_tfm;
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static DEFINE_STATIC_KEY_TRUE(crct10dif_fallback);
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static DEFINE_MUTEX(crc_t10dif_mutex);
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static struct work_struct crct10dif_rehash_work;
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static int crc_t10dif_notify(struct notifier_block *self, unsigned long val, void *data)
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{
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struct crypto_alg *alg = data;
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if (val != CRYPTO_MSG_ALG_LOADED ||
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strcmp(alg->cra_name, CRC_T10DIF_STRING))
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return NOTIFY_DONE;
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schedule_work(&crct10dif_rehash_work);
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return NOTIFY_OK;
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}
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static void crc_t10dif_rehash(struct work_struct *work)
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{
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struct crypto_shash *new, *old;
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mutex_lock(&crc_t10dif_mutex);
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old = rcu_dereference_protected(crct10dif_tfm,
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lockdep_is_held(&crc_t10dif_mutex));
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new = crypto_alloc_shash(CRC_T10DIF_STRING, 0, 0);
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if (IS_ERR(new)) {
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mutex_unlock(&crc_t10dif_mutex);
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return;
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}
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rcu_assign_pointer(crct10dif_tfm, new);
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mutex_unlock(&crc_t10dif_mutex);
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if (old) {
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synchronize_rcu();
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crypto_free_shash(old);
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} else {
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static_branch_disable(&crct10dif_fallback);
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}
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}
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static struct notifier_block crc_t10dif_nb = {
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.notifier_call = crc_t10dif_notify,
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};
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__u16 crc_t10dif_update(__u16 crc, const unsigned char *buffer, size_t len)
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{
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struct {
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struct shash_desc shash;
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__u16 crc;
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} desc;
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int err;
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if (static_branch_unlikely(&crct10dif_fallback))
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return crc_t10dif_generic(crc, buffer, len);
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rcu_read_lock();
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desc.shash.tfm = rcu_dereference(crct10dif_tfm);
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desc.crc = crc;
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err = crypto_shash_update(&desc.shash, buffer, len);
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rcu_read_unlock();
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BUG_ON(err);
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return desc.crc;
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}
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EXPORT_SYMBOL(crc_t10dif_update);
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__u16 crc_t10dif(const unsigned char *buffer, size_t len)
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{
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return crc_t10dif_update(0, buffer, len);
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}
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EXPORT_SYMBOL(crc_t10dif);
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static int __init crc_t10dif_mod_init(void)
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{
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INIT_WORK(&crct10dif_rehash_work, crc_t10dif_rehash);
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crypto_register_notifier(&crc_t10dif_nb);
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crc_t10dif_rehash(&crct10dif_rehash_work);
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return 0;
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}
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static void __exit crc_t10dif_mod_fini(void)
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{
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crypto_unregister_notifier(&crc_t10dif_nb);
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cancel_work_sync(&crct10dif_rehash_work);
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crypto_free_shash(rcu_dereference_protected(crct10dif_tfm, 1));
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}
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module_init(crc_t10dif_mod_init);
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module_exit(crc_t10dif_mod_fini);
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static int crc_t10dif_transform_show(char *buffer, const struct kernel_param *kp)
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{
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struct crypto_shash *tfm;
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int len;
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if (static_branch_unlikely(&crct10dif_fallback))
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return sprintf(buffer, "fallback\n");
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rcu_read_lock();
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tfm = rcu_dereference(crct10dif_tfm);
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len = snprintf(buffer, PAGE_SIZE, "%s\n",
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crypto_shash_driver_name(tfm));
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rcu_read_unlock();
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return len;
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}
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module_param_call(transform, NULL, crc_t10dif_transform_show, NULL, 0444);
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MODULE_DESCRIPTION("T10 DIF CRC calculation (library API)");
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MODULE_LICENSE("GPL");
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MODULE_SOFTDEP("pre: crct10dif");
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