Patch "hwrng: core - Don't use a stack buffer in add_early_randomness()" has been added to the 4.4-stable tree

Patch "hwrng: core - Don't use a stack buffer in add_early_randomness()" has been added to the 4.4-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

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

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     hwrng-core-don-t-use-a-stack-buffer-in-add_early_randomness.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 6d4952d9d9d4dc2bb9c0255d95a09405a1e958f7 Mon Sep 17 00:00:00 2001
From: Andrew Lutomirski <luto@kernel.org>
Date: Mon, 17 Oct 2016 10:06:27 -0700
Subject: hwrng: core - Don't use a stack buffer in add_early_randomness()

From: Andrew Lutomirski <luto@kernel.org>

commit 6d4952d9d9d4dc2bb9c0255d95a09405a1e958f7 upstream.

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 <mmullins@mmlx.us>
Tested-by: Matt Mullins <mmullins@mmlx.us>
Fixes: d3cc7996473a ("hwrng: fetch randomness only after device init")
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/char/hw_random/core.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- 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)


Patches currently in stable-queue which might be from luto@kernel.org are

queue-4.4/hwrng-core-don-t-use-a-stack-buffer-in-add_early_randomness.patch