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path: root/drivers/char/hw_random/core.c
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Diffstat (limited to 'drivers/char/hw_random/core.c')
-rw-r--r--drivers/char/hw_random/core.c215
1 files changed, 147 insertions, 68 deletions
diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
index 1500cfd..32a8a86 100644
--- a/drivers/char/hw_random/core.c
+++ b/drivers/char/hw_random/core.c
@@ -42,6 +42,7 @@
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/random.h>
+#include <linux/err.h>
#include <asm/uaccess.h>
@@ -53,7 +54,10 @@
static struct hwrng *current_rng;
static struct task_struct *hwrng_fill;
static LIST_HEAD(rng_list);
+/* Protects rng_list and current_rng */
static DEFINE_MUTEX(rng_mutex);
+/* Protects rng read functions, data_avail, rng_buffer and rng_fillbuf */
+static DEFINE_MUTEX(reading_mutex);
static int data_avail;
static u8 *rng_buffer, *rng_fillbuf;
static unsigned short current_quality;
@@ -66,6 +70,8 @@ module_param(default_quality, ushort, 0644);
MODULE_PARM_DESC(default_quality,
"default entropy content of hwrng per mill");
+static void drop_current_rng(void);
+static int hwrng_init(struct hwrng *rng);
static void start_khwrngd(void);
static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
@@ -81,13 +87,83 @@ static void add_early_randomness(struct hwrng *rng)
unsigned char bytes[16];
int bytes_read;
+ mutex_lock(&reading_mutex);
bytes_read = rng_get_data(rng, bytes, sizeof(bytes), 1);
+ mutex_unlock(&reading_mutex);
if (bytes_read > 0)
add_device_randomness(bytes, bytes_read);
}
-static inline int hwrng_init(struct hwrng *rng)
+static inline void cleanup_rng(struct kref *kref)
{
+ struct hwrng *rng = container_of(kref, struct hwrng, ref);
+
+ if (rng->cleanup)
+ rng->cleanup(rng);
+
+ complete(&rng->cleanup_done);
+}
+
+static int set_current_rng(struct hwrng *rng)
+{
+ int err;
+
+ BUG_ON(!mutex_is_locked(&rng_mutex));
+
+ err = hwrng_init(rng);
+ if (err)
+ return err;
+
+ drop_current_rng();
+ current_rng = rng;
+
+ return 0;
+}
+
+static void drop_current_rng(void)
+{
+ BUG_ON(!mutex_is_locked(&rng_mutex));
+ if (!current_rng)
+ return;
+
+ /* decrease last reference for triggering the cleanup */
+ kref_put(&current_rng->ref, cleanup_rng);
+ current_rng = NULL;
+}
+
+/* Returns ERR_PTR(), NULL or refcounted hwrng */
+static struct hwrng *get_current_rng(void)
+{
+ struct hwrng *rng;
+
+ if (mutex_lock_interruptible(&rng_mutex))
+ return ERR_PTR(-ERESTARTSYS);
+
+ rng = current_rng;
+ if (rng)
+ kref_get(&rng->ref);
+
+ mutex_unlock(&rng_mutex);
+ return rng;
+}
+
+static void put_rng(struct hwrng *rng)
+{
+ /*
+ * Hold rng_mutex here so we serialize in case they set_current_rng
+ * on rng again immediately.
+ */
+ mutex_lock(&rng_mutex);
+ if (rng)
+ kref_put(&rng->ref, cleanup_rng);
+ mutex_unlock(&rng_mutex);
+}
+
+static int hwrng_init(struct hwrng *rng)
+{
+ if (kref_get_unless_zero(&rng->ref))
+ goto skip_init;
+
if (rng->init) {
int ret;
@@ -95,6 +171,11 @@ static inline int hwrng_init(struct hwrng *rng)
if (ret)
return ret;
}
+
+ kref_init(&rng->ref);
+ reinit_completion(&rng->cleanup_done);
+
+skip_init:
add_early_randomness(rng);
current_quality = rng->quality ? : default_quality;
@@ -108,12 +189,6 @@ static inline int hwrng_init(struct hwrng *rng)
return 0;
}
-static inline void hwrng_cleanup(struct hwrng *rng)
-{
- if (rng && rng->cleanup)
- rng->cleanup(rng);
-}
-
static int rng_dev_open(struct inode *inode, struct file *filp)
{
/* enforce read-only access to this chrdev */
@@ -128,6 +203,7 @@ static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
int wait) {
int present;
+ BUG_ON(!mutex_is_locked(&reading_mutex));
if (rng->read)
return rng->read(rng, (void *)buffer, size, wait);
@@ -148,25 +224,27 @@ static ssize_t rng_dev_read(struct file *filp, char __user *buf,
ssize_t ret = 0;
int err = 0;
int bytes_read, len;
+ struct hwrng *rng;
while (size) {
- if (mutex_lock_interruptible(&rng_mutex)) {
- err = -ERESTARTSYS;
+ rng = get_current_rng();
+ if (IS_ERR(rng)) {
+ err = PTR_ERR(rng);
goto out;
}
-
- if (!current_rng) {
+ if (!rng) {
err = -ENODEV;
- goto out_unlock;
+ goto out;
}
+ mutex_lock(&reading_mutex);
if (!data_avail) {
- bytes_read = rng_get_data(current_rng, rng_buffer,
+ bytes_read = rng_get_data(rng, rng_buffer,
rng_buffer_size(),
!(filp->f_flags & O_NONBLOCK));
if (bytes_read < 0) {
err = bytes_read;
- goto out_unlock;
+ goto out_unlock_reading;
}
data_avail = bytes_read;
}
@@ -174,7 +252,7 @@ static ssize_t rng_dev_read(struct file *filp, char __user *buf,
if (!data_avail) {
if (filp->f_flags & O_NONBLOCK) {
err = -EAGAIN;
- goto out_unlock;
+ goto out_unlock_reading;
}
} else {
len = data_avail;
@@ -186,14 +264,15 @@ static ssize_t rng_dev_read(struct file *filp, char __user *buf,
if (copy_to_user(buf + ret, rng_buffer + data_avail,
len)) {
err = -EFAULT;
- goto out_unlock;
+ goto out_unlock_reading;
}
size -= len;
ret += len;
}
- mutex_unlock(&rng_mutex);
+ mutex_unlock(&reading_mutex);
+ put_rng(rng);
if (need_resched())
schedule_timeout_interruptible(1);
@@ -205,8 +284,10 @@ static ssize_t rng_dev_read(struct file *filp, char __user *buf,
}
out:
return ret ? : err;
-out_unlock:
- mutex_unlock(&rng_mutex);
+
+out_unlock_reading:
+ mutex_unlock(&reading_mutex);
+ put_rng(rng);
goto out;
}
@@ -239,16 +320,9 @@ static ssize_t hwrng_attr_current_store(struct device *dev,
err = -ENODEV;
list_for_each_entry(rng, &rng_list, list) {
if (strcmp(rng->name, buf) == 0) {
- if (rng == current_rng) {
- err = 0;
- break;
- }
- err = hwrng_init(rng);
- if (err)
- break;
- hwrng_cleanup(current_rng);
- current_rng = rng;
err = 0;
+ if (rng != current_rng)
+ err = set_current_rng(rng);
break;
}
}
@@ -261,17 +335,15 @@ static ssize_t hwrng_attr_current_show(struct device *dev,
struct device_attribute *attr,
char *buf)
{
- int err;
ssize_t ret;
- const char *name = "none";
+ struct hwrng *rng;
- err = mutex_lock_interruptible(&rng_mutex);
- if (err)
- return -ERESTARTSYS;
- if (current_rng)
- name = current_rng->name;
- ret = snprintf(buf, PAGE_SIZE, "%s\n", name);
- mutex_unlock(&rng_mutex);
+ rng = get_current_rng();
+ if (IS_ERR(rng))
+ return PTR_ERR(rng);
+
+ ret = snprintf(buf, PAGE_SIZE, "%s\n", rng ? rng->name : "none");
+ put_rng(rng);
return ret;
}
@@ -305,14 +377,14 @@ static DEVICE_ATTR(rng_available, S_IRUGO,
NULL);
-static void unregister_miscdev(void)
+static void __exit unregister_miscdev(void)
{
device_remove_file(rng_miscdev.this_device, &dev_attr_rng_available);
device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current);
misc_deregister(&rng_miscdev);
}
-static int register_miscdev(void)
+static int __init register_miscdev(void)
{
int err;
@@ -342,15 +414,22 @@ static int hwrng_fillfn(void *unused)
long rc;
while (!kthread_should_stop()) {
- if (!current_rng)
+ struct hwrng *rng;
+
+ rng = get_current_rng();
+ if (IS_ERR(rng) || !rng)
break;
- rc = rng_get_data(current_rng, rng_fillbuf,
+ mutex_lock(&reading_mutex);
+ rc = rng_get_data(rng, rng_fillbuf,
rng_buffer_size(), 1);
+ mutex_unlock(&reading_mutex);
+ put_rng(rng);
if (rc <= 0) {
pr_warn("hwrng: no data available\n");
msleep_interruptible(10000);
continue;
}
+ /* Outside lock, sure, but y'know: randomness. */
add_hwgenerator_randomness((void *)rng_fillbuf, rc,
rc * current_quality * 8 >> 10);
}
@@ -400,23 +479,16 @@ int hwrng_register(struct hwrng *rng)
goto out_unlock;
}
+ init_completion(&rng->cleanup_done);
+ complete(&rng->cleanup_done);
+
old_rng = current_rng;
- if (!old_rng) {
- err = hwrng_init(rng);
- if (err)
- goto out_unlock;
- current_rng = rng;
- }
err = 0;
if (!old_rng) {
- err = register_miscdev();
- if (err) {
- hwrng_cleanup(rng);
- current_rng = NULL;
+ err = set_current_rng(rng);
+ if (err)
goto out_unlock;
- }
}
- INIT_LIST_HEAD(&rng->list);
list_add_tail(&rng->list, &rng_list);
if (old_rng && !rng->init) {
@@ -439,42 +511,49 @@ EXPORT_SYMBOL_GPL(hwrng_register);
void hwrng_unregister(struct hwrng *rng)
{
- int err;
-
mutex_lock(&rng_mutex);
list_del(&rng->list);
if (current_rng == rng) {
- hwrng_cleanup(rng);
- if (list_empty(&rng_list)) {
- current_rng = NULL;
- } else {
- current_rng = list_entry(rng_list.prev, struct hwrng, list);
- err = hwrng_init(current_rng);
- if (err)
- current_rng = NULL;
+ drop_current_rng();
+ if (!list_empty(&rng_list)) {
+ struct hwrng *tail;
+
+ tail = list_entry(rng_list.prev, struct hwrng, list);
+
+ set_current_rng(tail);
}
}
+
if (list_empty(&rng_list)) {
- unregister_miscdev();
+ mutex_unlock(&rng_mutex);
if (hwrng_fill)
kthread_stop(hwrng_fill);
- }
+ } else
+ mutex_unlock(&rng_mutex);
- mutex_unlock(&rng_mutex);
+ wait_for_completion(&rng->cleanup_done);
}
EXPORT_SYMBOL_GPL(hwrng_unregister);
-static void __exit hwrng_exit(void)
+static int __init hwrng_modinit(void)
+{
+ return register_miscdev();
+}
+
+static void __exit hwrng_modexit(void)
{
mutex_lock(&rng_mutex);
BUG_ON(current_rng);
kfree(rng_buffer);
kfree(rng_fillbuf);
mutex_unlock(&rng_mutex);
+
+ unregister_miscdev();
}
-module_exit(hwrng_exit);
+module_init(hwrng_modinit);
+module_exit(hwrng_modexit);
MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
MODULE_LICENSE("GPL");

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