| Message ID | 34087343.u7K3uzbyiZ@tachyon.chronox.de (mailing list archive) |
|---|---|
| State | Changes Requested |
| Delegated to: | Herbert Xu |
| Headers | show |
On Wed, May 13, 2015 at 09:54:41PM +0200, Stephan Mueller wrote: > /* > + * Equivalent function to get_random_bytes with the difference that this > + * function blocks the request until the nonblocking_pool is initialized. > + */ > +void get_blocking_random_bytes(void *buf, int nbytes) > +{ > + if (unlikely(nonblocking_pool.initialized == 0)) > + wait_event_interruptible(urandom_init_wait, > + nonblocking_pool.initialized); > + extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0); So what if the wait was interrupted? You are going to extract entropy from an empty pool. Anyway, you still haven't addressed my primary concern with this model which is the potential for dead-lock. Sleeping for an open period of time like this in a work queue is bad form. It may also lead to dead-locks if whatever you're waiting for happened to use the same work thread. That's why I think you should simply provide a function and data pointer which random.c can then stash onto a list to call when the pool is ready. Cheers,
diff --git a/drivers/char/random.c b/drivers/char/random.c index 9cd6968..6f71354 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1245,6 +1245,20 @@ void get_random_bytes(void *buf, int nbytes) EXPORT_SYMBOL(get_random_bytes); /* + * Equivalent function to get_random_bytes with the difference that this + * function blocks the request until the nonblocking_pool is initialized. + */ +void get_blocking_random_bytes(void *buf, int nbytes) +{ + if (unlikely(nonblocking_pool.initialized == 0)) + wait_event_interruptible(urandom_init_wait, + nonblocking_pool.initialized); + extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0); +} +EXPORT_SYMBOL(get_blocking_random_bytes); + + +/* * This function will use the architecture-specific hardware random * number generator if it is available. The arch-specific hw RNG will * almost certainly be faster than what we can do in software, but it diff --git a/include/linux/random.h b/include/linux/random.h index b05856e..0926d78 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -14,6 +14,7 @@ extern void add_input_randomness(unsigned int type, unsigned int code, extern void add_interrupt_randomness(int irq, int irq_flags); extern void get_random_bytes(void *buf, int nbytes); +extern void get_blocking_random_bytes(void *buf, int nbytes); extern void get_random_bytes_arch(void *buf, int nbytes); void generate_random_uuid(unsigned char uuid_out[16]); extern int random_int_secret_init(void);
The added API calls provide a synchronous function call get_blocking_random_bytes where the caller is blocked until the nonblocking_pool is initialized. CC: Andreas Steffen <andreas.steffen@strongswan.org> CC: Theodore Ts'o <tytso@mit.edu> CC: Sandy Harris <sandyinchina@gmail.com> Signed-off-by: Stephan Mueller <smueller@chronox.de> --- drivers/char/random.c | 14 ++++++++++++++ include/linux/random.h | 1 + 2 files changed, 15 insertions(+)