crypto: atmel-sha - fix error management in atmel_sha_start()

This patch clarifies and fixes how errors should be handled by
atmel_sha_start().

For update operations, the previous code wrongly assumed that
(err != -EINPROGRESS) implies (err == 0). It's wrong because that doesn't
take the error cases (err < 0) into account.

This patch also adds many comments to detail all the possible returned
values and what should be done in each case.

Especially, when an error occurs, since atmel_sha_complete() has already
been called, hence releasing the hardware, atmel_sha_start() must not call
atmel_sha_finish_req() later otherwise atmel_sha_complete() would be
called a second time.

Signed-off-by: Cyrille Pitchen <cyrille.pitchen@atmel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 22 insertions, 5 deletions

diff --git a/drivers/crypto/atmel-sha.c b/drivers/crypto/atmel-sha.c
index bc033178d0e7..a9482023d7d3 100644
--- a/drivers/crypto/atmel-sha.c
+++ b/drivers/crypto/atmel-sha.c
@@ -1106,22 +1106,39 @@ static int atmel_sha_start(struct atmel_sha_dev *dd)
                                                 ctx->op, req->nbytes);
 
         err = atmel_sha_hw_init(dd);
-
         if (err)
-                goto err1;
+                return atmel_sha_complete(dd, err);
+
+        /*
+         * atmel_sha_update_req() and atmel_sha_final_req() can return either:
+         *  -EINPROGRESS: the hardware is busy and the SHA driver will resume
+         *                its job later in the done_task.
+         *                This is the main path.
+         *
+         * 0: the SHA driver can continue its job then release the hardware
+         *    later, if needed, with atmel_sha_finish_req().
+         *    This is the alternate path.
+         *
+         * < 0: an error has occurred so atmel_sha_complete(dd, err) has already
+         *      been called, hence the hardware has been released.
+         *      The SHA driver must stop its job without calling
+         *      atmel_sha_finish_req(), otherwise atmel_sha_complete() would be
+         *      called a second time.
+         *
+         * Please note that currently, atmel_sha_final_req() never returns 0.
+         */
 
         dd->resume = atmel_sha_done;
         if (ctx->op == SHA_OP_UPDATE) {
                 err = atmel_sha_update_req(dd);
-                if (err != -EINPROGRESS && (ctx->flags & SHA_FLAGS_FINUP))
+                if (!err && (ctx->flags & SHA_FLAGS_FINUP))
                         /* no final() after finup() */
                         err = atmel_sha_final_req(dd);
         } else if (ctx->op == SHA_OP_FINAL) {
                 err = atmel_sha_final_req(dd);
         }
 
-err1:
-        if (err != -EINPROGRESS)
+        if (!err)
                 /* done_task will not finish it, so do it here */
                 atmel_sha_finish_req(req, err);