random: fix the RNDRESEEDCRNG ioctl

The RNDRESEEDCRNG ioctl reseeds the primary_crng from itself, which
doesn't make sense.  Reseed it from the input_pool instead.

Fixes: d848e5f8 ("random: add new ioctl RNDRESEEDCRNG")
Cc: stable@vger.kernel.org
Cc: linux-crypto@vger.kernel.org
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Jann Horn <jannh@google.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: NJann Horn <jannh@google.com>
Acked-by: NArd Biesheuvel <ardb@kernel.org>
Signed-off-by: NEric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20210112192818.69921-1-ebiggers@kernel.orgSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/char/random.c

@@ -1972,7 +1972,7 @@ static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
 			return -EPERM;
 		if (crng_init < 2)
 			return -ENODATA;
-		crng_reseed(&primary_crng, NULL);
+		crng_reseed(&primary_crng, &input_pool);
 		crng_global_init_time = jiffies - 1;
 		return 0;
 	default: