crypto: drbg - set freed buffers to NULL

BugLink: http://bugs.launchpad.net/bugs/1778265
commit eea0d3ea7546961f69f55b26714ac8fd71c7c020 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/crypto/drbg.c b/crypto/drbg.c
index 4faa2781c964e290f8b28e752993b9a408d927b4..466a112a4446820ff655c3b72076c86d3c7e4f2d 100644 (file)
--- 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;