crypto: drbg - set freed buffers to NULL

smuellerDD · herbertx · commit eea0d3ea7546 · 2018-04-21T00:57:00.000+08:00
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: 3cfc3b9 ("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>
diff --git a/crypto/drbg.c b/crypto/drbg.c
@@ -1134,8 +1134,10 @@ static inline void drbg_dealloc_state(struct drbg_state *drbg)
 	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;
