[ 3.5.y.z extended stable ] Patch "crypto: api - Fix race condition in larval lookup" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    crypto: api - Fix race condition in larval lookup

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 27c9d1767985e6b42398ad494227742b42e0d6b2 Mon Sep 17 00:00:00 2001
From: Herbert Xu <herbert at gondor.apana.org.au>
Date: Sun, 8 Sep 2013 14:33:50 +1000
Subject: [PATCH] crypto: api - Fix race condition in larval lookup

commit 77dbd7a95e4a4f15264c333a9e9ab97ee27dc2aa upstream.

crypto_larval_lookup should only return a larval if it created one.
Any larval created by another entity must be processed through
crypto_larval_wait before being returned.

Otherwise this will lead to a larval being killed twice, which
will most likely lead to a crash.

Reported-by: Kees Cook <keescook at chromium.org>
Tested-by: Kees Cook <keescook at chromium.org>
Signed-off-by: Herbert Xu <herbert at gondor.apana.org.au>
[ luis: backported to 3.5: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 crypto/api.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/crypto/api.c b/crypto/api.c
index 033a714..cea3cf6 100644
--- a/crypto/api.c
+++ b/crypto/api.c
@@ -34,6 +34,8 @@ EXPORT_SYMBOL_GPL(crypto_alg_sem);
 BLOCKING_NOTIFIER_HEAD(crypto_chain);
 EXPORT_SYMBOL_GPL(crypto_chain);

+static struct crypto_alg *crypto_larval_wait(struct crypto_alg *alg);
+
 static inline struct crypto_alg *crypto_alg_get(struct crypto_alg *alg)
 {
 	atomic_inc(&alg->cra_refcnt);
@@ -150,8 +152,11 @@ static struct crypto_alg *crypto_larval_add(const char *name, u32 type,
 	}
 	up_write(&crypto_alg_sem);

-	if (alg != &larval->alg)
+	if (alg != &larval->alg) {
 		kfree(larval);
+		if (crypto_is_larval(alg))
+			alg = crypto_larval_wait(alg);
+	}

 	return alg;
 }
--
1.8.3.2