From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Fri, 6 Dec 2019 05:55:17 +0000 (+0800)
Subject: crypto: api - Check spawn->alg under lock in crypto_drop_spawn
X-Git-Tag: v4.19.103~123
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=12fa296ad27e784d8a9201c953a3e3b2542a75b1;p=thirdparty%2Fkernel%2Fstable.git

crypto: api - Check spawn->alg under lock in crypto_drop_spawn

commit 7db3b61b6bba4310f454588c2ca6faf2958ad79f upstream.

We need to check whether spawn->alg is NULL under lock as otherwise
the algorithm could be removed from under us after we have checked
it and found it to be non-NULL.  This could cause us to remove the
spawn from a non-existent list.

Fixes: 7ede5a5ba55a ("crypto: api - Fix crypto_drop_spawn crash...")
Cc: <stable@vger.kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/crypto/algapi.c b/crypto/algapi.c
index c0755cf4f53f8..6d578b7e59a42 100644
--- a/crypto/algapi.c
+++ b/crypto/algapi.c
@@ -649,11 +649,9 @@ EXPORT_SYMBOL_GPL(crypto_grab_spawn);
 
 void crypto_drop_spawn(struct crypto_spawn *spawn)
 {
-	if (!spawn->alg)
-		return;
-
 	down_write(&crypto_alg_sem);
-	list_del(&spawn->list);
+	if (spawn->alg)
+		list_del(&spawn->list);
 	up_write(&crypto_alg_sem);
 }
 EXPORT_SYMBOL_GPL(crypto_drop_spawn);