hwrng: core - Don't use a stack buffer in add_early_randomness()

hw_random carefully avoids using a stack buffer except in add_early_randomness(). This causes a crash in virtio_rng if CONFIG_VMAP_STACK=y. Reported-by: Matt Mullins <[email protected]> Tested-by: Matt Mullins <[email protected]> Fixes: d3cc799 ("hwrng: fetch randomness only after device init") Signed-off-by: Andy Lutomirski <[email protected]> Signed-off-by: Herbert Xu <[email protected]>
voipac · Oct 19, 2016 · 6d4952d · 6d4952d
1 parent 1001354
commit 6d4952d
Showing 1 changed file with 3 additions and 3 deletions.
diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
@@ -84,14 +84,14 @@ static size_t rng_buffer_size(void)
 
 static void add_early_randomness(struct hwrng *rng)
 {
-	unsigned char bytes[16];
 	int bytes_read;
+	size_t size = min_t(size_t, 16, rng_buffer_size());
 
 	mutex_lock(&reading_mutex);
-	bytes_read = rng_get_data(rng, bytes, sizeof(bytes), 1);
+	bytes_read = rng_get_data(rng, rng_buffer, size, 1);
 	mutex_unlock(&reading_mutex);
 	if (bytes_read > 0)
-		add_device_randomness(bytes, bytes_read);
+		add_device_randomness(rng_buffer, bytes_read);
 }
 
 static inline void cleanup_rng(struct kref *kref)