[PATCH 098/104] crypto: api - Fix race condition in larval lookup

Luis Henriques luis.henriques at canonical.com
Mon Sep 30 10:11:15 UTC 2013 -stable review patch.  If anyone has any objections, please let me know.


From: Herbert Xu <herbert at gondor.apana.org.au>

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);
+static struct crypto_alg *crypto_larval_wait(struct crypto_alg *alg);
 static inline struct crypto_alg *crypto_alg_get(struct crypto_alg *alg)
@@ -150,8 +152,11 @@ static struct crypto_alg *crypto_larval_add(const char *name, u32 type,
-	if (alg != &larval->alg)
+	if (alg != &larval->alg) {
+		if (crypto_is_larval(alg))
+			alg = crypto_larval_wait(alg);
+	}
 	return alg;

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