Commit f3c2682b authored by Jason A. Donenfeld's avatar Jason A. Donenfeld
Browse files

random: provide notifier for VM fork 



Drivers such as WireGuard need to learn when VMs fork in order to clear
sessions. This commit provides a simple notifier_block for that, with a
register and unregister function. When no VM fork detection is compiled
in, this turns into a no-op, similar to how the power notifier works.

Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Cc: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarJason A. Donenfeld <Jason@zx2c4.com>
parent 5acd3548

drivers/char/random.c

+15 −0
Original line number Diff line number Diff line
@@ -1140,6 +1140,8 @@ void add_bootloader_randomness(const void *buf, size_t size) 
EXPORT_SYMBOL_GPL(add_bootloader_randomness);



#if IS_ENABLED(CONFIG_VMGENID)

static BLOCKING_NOTIFIER_HEAD(vmfork_chain);



/*

 * Handle a new unique VM ID, which is unique, not secret, so we

 * don't credit it, but we do immediately force a reseed after so
@@ -1152,10 +1154,23 @@ void add_vmfork_randomness(const void *unique_vm_id, size_t size) 
		crng_reseed(true);

		pr_notice("crng reseeded due to virtual machine fork\n");

	}

	blocking_notifier_call_chain(&vmfork_chain, 0, NULL);

}

#if IS_MODULE(CONFIG_VMGENID)

EXPORT_SYMBOL_GPL(add_vmfork_randomness);

#endif



int register_random_vmfork_notifier(struct notifier_block *nb)

{

	return blocking_notifier_chain_register(&vmfork_chain, nb);

}

EXPORT_SYMBOL_GPL(register_random_vmfork_notifier);



int unregister_random_vmfork_notifier(struct notifier_block *nb)

{

	return blocking_notifier_chain_unregister(&vmfork_chain, nb);

}

EXPORT_SYMBOL_GPL(unregister_random_vmfork_notifier);

#endif



struct fast_pool {

include/linux/random.h

+5 −0
Original line number Diff line number Diff line
@@ -32,6 +32,11 @@ extern void add_hwgenerator_randomness(const void *buffer, size_t count, 
				       size_t entropy);

#if IS_ENABLED(CONFIG_VMGENID)

extern void add_vmfork_randomness(const void *unique_vm_id, size_t size);

extern int register_random_vmfork_notifier(struct notifier_block *nb);

extern int unregister_random_vmfork_notifier(struct notifier_block *nb);

#else

static inline int register_random_vmfork_notifier(struct notifier_block *nb) { return 0; }

static inline int unregister_random_vmfork_notifier(struct notifier_block *nb) { return 0; }

#endif



extern void get_random_bytes(void *buf, size_t nbytes);