crypto: api - Redo lookup on EEXIST

When two crypto algorithm lookups occur at the same time with
different names for the same algorithm, e.g., ctr(aes-generic)
and ctr(aes), they will both be instantiated.  However, only one
of them can be registered.  The second instantiation will fail
with EEXIST.

Avoid failing the second lookup by making it retry, but only once
because there are tricky names such as gcm_base(ctr(aes),ghash)
that will always fail, despite triggering instantiation and EEXIST.

Reported-by: Ingo Franzki <ifranzki@linux.ibm.com>
Fixes: 2825982d9d66 ("[CRYPTO] api: Added event notification")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/crypto/api.c b/crypto/api.c
index 133d9b62692272c4d93a247b12eff5978eb14d68..5724d62e9d0780a3d56d1d136b0e6124b3269b4d 100644 (file)
--- a/crypto/api.c
+++ b/crypto/api.c
@@ -219,10 +219,19 @@ again:
                if (crypto_is_test_larval(larval))
                        crypto_larval_kill(larval);
                alg = ERR_PTR(-ETIMEDOUT);
-       } else if (!alg) {
+       } else if (!alg || PTR_ERR(alg) == -EEXIST) {
+               int err = alg ? -EEXIST : -EAGAIN;
+
+               /*
+                * EEXIST is expected because two probes can be scheduled
+                * at the same time with one using alg_name and the other
+                * using driver_name.  Do a re-lookup but do not retry in
+                * case we hit a quirk like gcm_base(ctr(aes),...) which
+                * will never match.
+                */
                alg = &larval->alg;
                alg = crypto_alg_lookup(alg->cra_name, type, mask) ?:
-                     ERR_PTR(-EAGAIN);
+                     ERR_PTR(err);
        } else if (IS_ERR(alg))
                ;
        else if (crypto_is_test_larval(larval) &&