crypto: Do not fail for EINTR during qcrypto_random_bytes

We can always get EINTR for read; /dev/urandom is no exception.

Rearrange the order of tests for likelihood; allow degenerate buflen==0
case to perform a no-op zero-length read.  This means that the normal
success path is a straight line with a single test for success.

Reviewed-by: Laurent Vivier <lvivier@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

1 files changed, 15 insertions, 21 deletions

diff --git a/crypto/random-platform.c b/crypto/random-platform.c
index f995fc0ef1..260b64564d 100644
--- a/crypto/random-platform.c
+++ b/crypto/random-platform.c
@@ -65,29 +65,23 @@ int qcrypto_random_bytes(uint8_t *buf G_GNUC_UNUSED,
                          "Unable to read random bytes");
         return -1;
     }
-
-    return 0;
 #else
-    int ret = -1;
-    int got;
-
-    while (buflen > 0) {
-        got = read(fd, buf, buflen);
-        if (got < 0) {
-            error_setg_errno(errp, errno,
-                             "Unable to read random bytes");
-            goto cleanup;
-        } else if (!got) {
-            error_setg(errp,
-                       "Unexpected EOF reading random bytes");
-            goto cleanup;
+    while (1) {
+        ssize_t got = read(fd, buf, buflen);
+        if (likely(got == buflen)) {
+            return 0;
+        }
+        if (got > 0) {
+            buflen -= got;
+            buf += got;
+        } else if (got == 0) {
+            error_setg(errp, "Unexpected EOF reading random bytes");
+            return -1;
+        } else if (errno != EINTR) {
+            error_setg_errno(errp, errno, "Unable to read random bytes");
+            return -1;
         }
-        buflen -= got;
-        buf += got;
     }
-
-    ret = 0;
- cleanup:
-    return ret;
 #endif
+    return 0;
 }