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@chromium.org>
Tested-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/crypto/api.c b/crypto/api.c
index 033a7147e5ebc4317b3bf082f090e8f2c2c8c115..cea3cf6c9897c57dedd9856273f288cc2e913969 100644 (file)
--- 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;
 }