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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/crypto/api.c b/crypto/api.c
index 033a714..4f98dd5 100644 (file)
--- a/crypto/api.c
+++ b/crypto/api.c
@@ -40,6 +40,8 @@ static inline struct crypto_alg *crypto_alg_get(struct crypto_alg *alg)
        return alg;
 }
 
+static struct crypto_alg *crypto_larval_wait(struct crypto_alg *alg);
+
 struct crypto_alg *crypto_mod_get(struct crypto_alg *alg)
 {
        return try_module_get(alg->cra_module) ? crypto_alg_get(alg) : NULL;
@@ -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;
 }