linux-kernel - [PATCH 4/4] char/tpm: Less checks in tpm_ibmvtpm

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Date:   Mon, 16 Oct 2017 19:34:56 +0200
From:   SF Markus Elfring <elfring@...rs.sourceforge.net>
To:     linux-integrity@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Corentin Labbe <clabbe.montjoie@...il.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
        Jerry Snitselaar <jsnitsel@...hat.com>,
        Kenneth Goldman <kgold@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nayna Jain <nayna@...ux.vnet.ibm.com>,
        Paul Mackerras <paulus@...ba.org>,
        Peter Hüwe <PeterHuewe@....de>,
        Stefan Berger <stefanb@...ux.vnet.ibm.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        kernel-janitors@...r.kernel.org
Subject: [PATCH 4/4] char/tpm: Less checks in tpm_ibmvtpm_probe() after error
 detection

From: Markus Elfring <elfring@...rs.sourceforge.net>
Date: Mon, 16 Oct 2017 19:00:34 +0200

Two pointer checks could be repeated by the tpm_ibmvtpm_probe() function
during error handling even if the relevant properties can be determined
for the involved variables before by source code analysis.

* Return directly after a call of the function "kzalloc" failed
  at the beginning.

* Adjust jump targets so that extra checks can be omitted at the end.

Signed-off-by: Markus Elfring <elfring@...rs.sourceforge.net>
---
 drivers/char/tpm/tpm_ibmvtpm.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/drivers/char/tpm/tpm_ibmvtpm.c b/drivers/char/tpm/tpm_ibmvtpm.c
index a4b462a77b99..b8dda7546f64 100644
--- a/drivers/char/tpm/tpm_ibmvtpm.c
+++ b/drivers/char/tpm/tpm_ibmvtpm.c
@@ -610,7 +610,7 @@ static int tpm_ibmvtpm_probe(struct vio_dev *vio_dev,
 
 	ibmvtpm = kzalloc(sizeof(*ibmvtpm), GFP_KERNEL);
 	if (!ibmvtpm)
-		goto cleanup;
+		return -ENOMEM;
 
 	ibmvtpm->dev = dev;
 	ibmvtpm->vdev = vio_dev;
@@ -619,7 +619,7 @@ static int tpm_ibmvtpm_probe(struct vio_dev *vio_dev,
 	crq_q->crq_addr = (struct ibmvtpm_crq *)get_zeroed_page(GFP_KERNEL);
 	if (!crq_q->crq_addr) {
 		dev_err(dev, "Unable to allocate memory for crq_addr\n");
-		goto cleanup;
+		goto free_tpm;
 	}
 
 	crq_q->num_entry = CRQ_RES_BUF_SIZE / sizeof(*crq_q->crq_addr);
@@ -629,7 +629,7 @@ static int tpm_ibmvtpm_probe(struct vio_dev *vio_dev,
 
 	if (dma_mapping_error(dev, ibmvtpm->crq_dma_handle)) {
 		dev_err(dev, "dma mapping failed\n");
-		goto cleanup;
+		goto free_page;
 	}
 
 	rc = plpar_hcall_norets(H_REG_CRQ, vio_dev->unit_address,
@@ -683,13 +683,10 @@ static int tpm_ibmvtpm_probe(struct vio_dev *vio_dev,
 reg_crq_cleanup:
 	dma_unmap_single(dev, ibmvtpm->crq_dma_handle, CRQ_RES_BUF_SIZE,
 			 DMA_BIDIRECTIONAL);
-cleanup:
-	if (ibmvtpm) {
-		if (crq_q->crq_addr)
-			free_page((unsigned long)crq_q->crq_addr);
-		kfree(ibmvtpm);
-	}
-
+free_page:
+	free_page((unsigned long)crq_q->crq_addr);
+free_tpm:
+	kfree(ibmvtpm);
 	return rc;
 }
 
-- 
2.14.2