Commit 0768ae32 authored Jul 13, 2022 by Eric Biggers

ANDROID: allow add_hwgenerator_randomness() from non-kthread



A recent LTS change causes add_hwgenerator_randomness() to crash when
called from a non-kthread task.  This shouldn't be a problem, since this
function should only be called by the HWRNG framework.  However, on this
branch it is part of the KMI since a vendor module is using it
inappropriately by calling it during early init.  (Note that
add_bootloader_randomness() would be a better fit for the use case.)

To prevent a crash in this case, restore support for
add_hwgenerator_randomness() being called from a non-kthread task.

This change isn't currently needed in 5.4 or newer kernels, as
add_hwgenerator_randomness() isn't part of the KMI there.

Bug: 238701371
Fixes: 8bc7018f ("random: do not use batches when !crng_ready()")
Change-Id: I0b86743deb30f54b8f838a36eea740b370a30a8b
Signed-off-by: Eric Biggers <ebiggers@google.com>

parent 79651a7a

drivers/char/random.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -873,7 +873,8 @@ void add_hwgenerator_randomness(const char *buf, size_t len, size_t entropy)
		* Throttle writing to once every CRNG_RESEED_INTERVAL, unless
		* we're not yet initialized.
		*/
		if (!kthread_should_stop() && crng_ready())
		if ((current->flags & PF_KTHREAD) &&
		!kthread_should_stop() && crng_ready())
		schedule_timeout_interruptible(CRNG_RESEED_INTERVAL);
		}
		EXPORT_SYMBOL_GPL(add_hwgenerator_randomness);