From eea0d3ea7546961f69f55b26714ac8fd71c7c020 Mon Sep 17 00:00:00 2001
From: Stephan Mueller <smueller@chronox.de>
Date: Thu, 12 Apr 2018 08:40:55 +0200
Subject: [PATCH] crypto: drbg - set freed buffers to NULL
Git-commit: eea0d3ea7546961f69f55b26714ac8fd71c7c020
Patch-mainline: v4.17-rc3
References: bsc#1051510

During freeing of the internal buffers used by the DRBG, set the pointer
to NULL. It is possible that the context with the freed buffers is
reused. In case of an error during initialization where the pointers
do not yet point to allocated memory, the NULL value prevents a double
free.

Cc: stable@vger.kernel.org
Fixes: 3cfc3b9721123 ("crypto: drbg - use aligned buffers")
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Reported-by: syzbot+75397ee3df5c70164154@syzkaller.appspotmail.com
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 crypto/drbg.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/crypto/drbg.c
+++ b/crypto/drbg.c
@@ -1134,8 +1134,10 @@ static inline void drbg_dealloc_state(st
 	if (!drbg)
 		return;
 	kzfree(drbg->Vbuf);
+	drbg->Vbuf = NULL;
 	drbg->V = NULL;
 	kzfree(drbg->Cbuf);
+	drbg->Cbuf = NULL;
 	drbg->C = NULL;
 	kzfree(drbg->scratchpadbuf);
 	drbg->scratchpadbuf = NULL;