* [PATCH 0/2] crc-t10dif library improvements
@ 2020-06-10 6:39 Eric Biggers
2020-06-10 6:39 ` [PATCH 1/2] crc-t10dif: use fallback in initial state Eric Biggers
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: Eric Biggers @ 2020-06-10 6:39 UTC (permalink / raw)
To: linux-crypto; +Cc: Martin K . Petersen
This series makes some more improvements to lib/crc-t10dif.c, as discussed at
https://lkml.kernel.org/linux-crypto/20200604063324.GA28813@gondor.apana.org.au/T/#u
This applies on top of Herbert's
"[v2 PATCH] crc-t10dif: Fix potential crypto notify dead-lock".
Eric Biggers (2):
crc-t10dif: use fallback in initial state
crc-t10dif: clean up some more things
lib/crc-t10dif.c | 61 +++++++++++++++++-------------------------------
1 file changed, 21 insertions(+), 40 deletions(-)
--
2.26.2
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH 1/2] crc-t10dif: use fallback in initial state
2020-06-10 6:39 [PATCH 0/2] crc-t10dif library improvements Eric Biggers
@ 2020-06-10 6:39 ` Eric Biggers
2020-06-10 6:39 ` [PATCH 2/2] crc-t10dif: clean up some more things Eric Biggers
2020-06-18 7:58 ` [PATCH 0/2] crc-t10dif library improvements Herbert Xu
2 siblings, 0 replies; 4+ messages in thread
From: Eric Biggers @ 2020-06-10 6:39 UTC (permalink / raw)
To: linux-crypto; +Cc: Martin K . Petersen
From: Eric Biggers <ebiggers@google.com>
Currently the crc-t10dif module starts out with the fallback disabled
and crct10dif_tfm == NULL. crc_t10dif_mod_init() tries to allocate
crct10dif_tfm, and if it fails it enables the fallback.
This is backwards because it means that any call to crc_t10dif() prior
to module_init (which could theoretically happen from built-in code)
will crash rather than use the fallback as expected. Also, it means
that if the initial tfm allocation fails, then the fallback stays
permanently enabled even if a crct10dif implementation is loaded later.
Change it to use the more logical solution of starting with the fallback
enabled, and disabling the fallback when a tfm gets allocated for the
first time. This change also ends up simplifying the code.
Also take the opportunity to convert the code to use the new static_key
API, which is much less confusing than the old and deprecated one.
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
lib/crc-t10dif.c | 37 ++++++++++---------------------------
1 file changed, 10 insertions(+), 27 deletions(-)
diff --git a/lib/crc-t10dif.c b/lib/crc-t10dif.c
index c9acf1c12cfcb4..af3613367ef944 100644
--- a/lib/crc-t10dif.c
+++ b/lib/crc-t10dif.c
@@ -17,7 +17,7 @@
#include <linux/notifier.h>
static struct crypto_shash __rcu *crct10dif_tfm;
-static struct static_key crct10dif_fallback __read_mostly;
+static DEFINE_STATIC_KEY_TRUE(crct10dif_fallback);
static DEFINE_MUTEX(crc_t10dif_mutex);
static struct work_struct crct10dif_rehash_work;
@@ -26,7 +26,6 @@ static int crc_t10dif_notify(struct notifier_block *self, unsigned long val, voi
struct crypto_alg *alg = data;
if (val != CRYPTO_MSG_ALG_LOADED ||
- static_key_false(&crct10dif_fallback) ||
strncmp(alg->cra_name, CRC_T10DIF_STRING, strlen(CRC_T10DIF_STRING)))
return 0;
@@ -41,10 +40,6 @@ static void crc_t10dif_rehash(struct work_struct *work)
mutex_lock(&crc_t10dif_mutex);
old = rcu_dereference_protected(crct10dif_tfm,
lockdep_is_held(&crc_t10dif_mutex));
- if (!old) {
- mutex_unlock(&crc_t10dif_mutex);
- return;
- }
new = crypto_alloc_shash("crct10dif", 0, 0);
if (IS_ERR(new)) {
mutex_unlock(&crc_t10dif_mutex);
@@ -53,8 +48,12 @@ static void crc_t10dif_rehash(struct work_struct *work)
rcu_assign_pointer(crct10dif_tfm, new);
mutex_unlock(&crc_t10dif_mutex);
- synchronize_rcu();
- crypto_free_shash(old);
+ if (old) {
+ synchronize_rcu();
+ crypto_free_shash(old);
+ } else {
+ static_branch_disable(&crct10dif_fallback);
+ }
}
static struct notifier_block crc_t10dif_nb = {
@@ -69,7 +68,7 @@ __u16 crc_t10dif_update(__u16 crc, const unsigned char *buffer, size_t len)
} desc;
int err;
- if (static_key_false(&crct10dif_fallback))
+ if (static_branch_unlikely(&crct10dif_fallback))
return crc_t10dif_generic(crc, buffer, len);
rcu_read_lock();
@@ -93,18 +92,9 @@ EXPORT_SYMBOL(crc_t10dif);
static int __init crc_t10dif_mod_init(void)
{
- struct crypto_shash *tfm;
-
INIT_WORK(&crct10dif_rehash_work, crc_t10dif_rehash);
crypto_register_notifier(&crc_t10dif_nb);
- mutex_lock(&crc_t10dif_mutex);
- tfm = crypto_alloc_shash("crct10dif", 0, 0);
- if (IS_ERR(tfm)) {
- static_key_slow_inc(&crct10dif_fallback);
- tfm = NULL;
- }
- RCU_INIT_POINTER(crct10dif_tfm, tfm);
- mutex_unlock(&crc_t10dif_mutex);
+ crc_t10dif_rehash(&crct10dif_rehash_work);
return 0;
}
@@ -124,20 +114,13 @@ static int crc_t10dif_transform_show(char *buffer, const struct kernel_param *kp
const char *name;
int len;
- if (static_key_false(&crct10dif_fallback))
+ if (static_branch_unlikely(&crct10dif_fallback))
return sprintf(buffer, "fallback\n");
rcu_read_lock();
tfm = rcu_dereference(crct10dif_tfm);
- if (!tfm) {
- len = sprintf(buffer, "init\n");
- goto unlock;
- }
-
name = crypto_tfm_alg_driver_name(crypto_shash_tfm(tfm));
len = sprintf(buffer, "%s\n", name);
-
-unlock:
rcu_read_unlock();
return len;
--
2.26.2
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH 2/2] crc-t10dif: clean up some more things
2020-06-10 6:39 [PATCH 0/2] crc-t10dif library improvements Eric Biggers
2020-06-10 6:39 ` [PATCH 1/2] crc-t10dif: use fallback in initial state Eric Biggers
@ 2020-06-10 6:39 ` Eric Biggers
2020-06-18 7:58 ` [PATCH 0/2] crc-t10dif library improvements Herbert Xu
2 siblings, 0 replies; 4+ messages in thread
From: Eric Biggers @ 2020-06-10 6:39 UTC (permalink / raw)
To: linux-crypto; +Cc: Martin K . Petersen
From: Eric Biggers <ebiggers@google.com>
- Correctly compare the algorithm name in crc_t10dif_notify().
- Use proper NOTIFY_* status codes instead of 0.
- Consistently use CRC_T10DIF_STRING instead of "crct10dif" directly.
- Use a proper type for the shash_desc context.
- Use crypto_shash_driver_name() instead of open-coding it.
- Make crc_t10dif_transform_show() use snprintf() rather than sprintf().
This isn't actually necessary since the buffer has size PAGE_SIZE
and CRYPTO_MAX_ALG_NAME < PAGE_SIZE, but it's good practice.
- Give the "transform" sysfs file mode 0444 rather than 0644,
since it doesn't implement a setter method.
- Adjust the module description to not be the same as crct10dif-generic.
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
lib/crc-t10dif.c | 24 +++++++++++-------------
1 file changed, 11 insertions(+), 13 deletions(-)
diff --git a/lib/crc-t10dif.c b/lib/crc-t10dif.c
index af3613367ef944..1ed2ed4870971e 100644
--- a/lib/crc-t10dif.c
+++ b/lib/crc-t10dif.c
@@ -26,11 +26,11 @@ static int crc_t10dif_notify(struct notifier_block *self, unsigned long val, voi
struct crypto_alg *alg = data;
if (val != CRYPTO_MSG_ALG_LOADED ||
- strncmp(alg->cra_name, CRC_T10DIF_STRING, strlen(CRC_T10DIF_STRING)))
- return 0;
+ strcmp(alg->cra_name, CRC_T10DIF_STRING))
+ return NOTIFY_DONE;
schedule_work(&crct10dif_rehash_work);
- return 0;
+ return NOTIFY_OK;
}
static void crc_t10dif_rehash(struct work_struct *work)
@@ -40,7 +40,7 @@ static void crc_t10dif_rehash(struct work_struct *work)
mutex_lock(&crc_t10dif_mutex);
old = rcu_dereference_protected(crct10dif_tfm,
lockdep_is_held(&crc_t10dif_mutex));
- new = crypto_alloc_shash("crct10dif", 0, 0);
+ new = crypto_alloc_shash(CRC_T10DIF_STRING, 0, 0);
if (IS_ERR(new)) {
mutex_unlock(&crc_t10dif_mutex);
return;
@@ -64,7 +64,7 @@ __u16 crc_t10dif_update(__u16 crc, const unsigned char *buffer, size_t len)
{
struct {
struct shash_desc shash;
- char ctx[2];
+ __u16 crc;
} desc;
int err;
@@ -73,14 +73,13 @@ __u16 crc_t10dif_update(__u16 crc, const unsigned char *buffer, size_t len)
rcu_read_lock();
desc.shash.tfm = rcu_dereference(crct10dif_tfm);
- *(__u16 *)desc.ctx = crc;
-
+ desc.crc = crc;
err = crypto_shash_update(&desc.shash, buffer, len);
rcu_read_unlock();
BUG_ON(err);
- return *(__u16 *)desc.ctx;
+ return desc.crc;
}
EXPORT_SYMBOL(crc_t10dif_update);
@@ -111,7 +110,6 @@ module_exit(crc_t10dif_mod_fini);
static int crc_t10dif_transform_show(char *buffer, const struct kernel_param *kp)
{
struct crypto_shash *tfm;
- const char *name;
int len;
if (static_branch_unlikely(&crct10dif_fallback))
@@ -119,15 +117,15 @@ static int crc_t10dif_transform_show(char *buffer, const struct kernel_param *kp
rcu_read_lock();
tfm = rcu_dereference(crct10dif_tfm);
- name = crypto_tfm_alg_driver_name(crypto_shash_tfm(tfm));
- len = sprintf(buffer, "%s\n", name);
+ len = snprintf(buffer, PAGE_SIZE, "%s\n",
+ crypto_shash_driver_name(tfm));
rcu_read_unlock();
return len;
}
-module_param_call(transform, NULL, crc_t10dif_transform_show, NULL, 0644);
+module_param_call(transform, NULL, crc_t10dif_transform_show, NULL, 0444);
-MODULE_DESCRIPTION("T10 DIF CRC calculation");
+MODULE_DESCRIPTION("T10 DIF CRC calculation (library API)");
MODULE_LICENSE("GPL");
MODULE_SOFTDEP("pre: crct10dif");
--
2.26.2
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH 0/2] crc-t10dif library improvements
2020-06-10 6:39 [PATCH 0/2] crc-t10dif library improvements Eric Biggers
2020-06-10 6:39 ` [PATCH 1/2] crc-t10dif: use fallback in initial state Eric Biggers
2020-06-10 6:39 ` [PATCH 2/2] crc-t10dif: clean up some more things Eric Biggers
@ 2020-06-18 7:58 ` Herbert Xu
2 siblings, 0 replies; 4+ messages in thread
From: Herbert Xu @ 2020-06-18 7:58 UTC (permalink / raw)
To: Eric Biggers; +Cc: linux-crypto, martin.petersen
Eric Biggers <ebiggers@kernel.org> wrote:
> This series makes some more improvements to lib/crc-t10dif.c, as discussed at
> https://lkml.kernel.org/linux-crypto/20200604063324.GA28813@gondor.apana.org.au/T/#u
>
> This applies on top of Herbert's
> "[v2 PATCH] crc-t10dif: Fix potential crypto notify dead-lock".
>
> Eric Biggers (2):
> crc-t10dif: use fallback in initial state
> crc-t10dif: clean up some more things
>
> lib/crc-t10dif.c | 61 +++++++++++++++++-------------------------------
> 1 file changed, 21 insertions(+), 40 deletions(-)
All applied. Thanks.
--
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
^ permalink raw reply [flat|nested] 4+ messages in thread
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