linux-kernel - [PATCH 8/9] um/drivers/vector_user: Less checks in user_init_tap

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Date:   Sun, 11 Mar 2018 16:23:40 +0100
From:   SF Markus Elfring <elfring@...rs.sourceforge.net>
To:     user-mode-linux-devel@...ts.sourceforge.net,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Jeff Dike <jdike@...toit.com>,
        Richard Weinberger <richard@....at>
Cc:     user-mode-linux-user@...ts.sourceforge.net,
        kernel-janitors@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH 8/9] um/drivers/vector_user: Less checks in
 user_init_tap_fds() after error detection

From: Markus Elfring <elfring@...rs.sourceforge.net>
Date: Sun, 11 Mar 2018 15:43:31 +0100

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

* Adjust jump targets.

* Delete three sanity checks and an initialisation (for the local
  variable "result") which became unnecessary with this refactoring.

Signed-off-by: Markus Elfring <elfring@...rs.sourceforge.net>
---
 arch/um/drivers/vector_user.c | 31 +++++++++++++++----------------
 1 file changed, 15 insertions(+), 16 deletions(-)

diff --git a/arch/um/drivers/vector_user.c b/arch/um/drivers/vector_user.c
index 5e78723c34d4..bd625034a0f0 100644
--- a/arch/um/drivers/vector_user.c
+++ b/arch/um/drivers/vector_user.c
@@ -123,18 +123,18 @@ static struct vector_fds *user_init_tap_fds(struct arglist *ifspec)
 	struct sockaddr_ll sock;
 	int err = -ENOMEM, offload;
 	char *iface;
-	struct vector_fds *result = NULL;
+	struct vector_fds *result;
 
 	iface = uml_vector_fetch_arg(ifspec, TOKEN_IFNAME);
 	if (iface == NULL) {
 		printk(UM_KERN_ERR "uml_tap: failed to parse interface spec\n");
-		goto tap_cleanup;
+		goto report_failure;
 	}
 
 	result = uml_kmalloc(sizeof(struct vector_fds), UM_GFP_KERNEL);
 	if (result == NULL) {
 		printk(UM_KERN_ERR "uml_tap: failed to allocate file descriptors\n");
-		goto tap_cleanup;
+		goto report_failure;
 	}
 	result->rx_fd = -1;
 	result->tx_fd = -1;
@@ -146,7 +146,7 @@ static struct vector_fds *user_init_tap_fds(struct arglist *ifspec)
 	fd = open(PATH_NET_TUN, O_RDWR);
 	if (fd < 0) {
 		printk(UM_KERN_ERR "uml_tap: failed to open tun device\n");
-		goto tap_cleanup;
+		goto free_result;
 	}
 	result->tx_fd = fd;
 	memset(&ifr, 0, sizeof(ifr));
@@ -156,7 +156,7 @@ static struct vector_fds *user_init_tap_fds(struct arglist *ifspec)
 	err = ioctl(fd, TUNSETIFF, (void *) &ifr);
 	if (err != 0) {
 		printk(UM_KERN_ERR "uml_tap: failed to select tap interface\n");
-		goto tap_cleanup;
+		goto close_tx_fd;
 	}
 
 	offload = TUN_F_CSUM | TUN_F_TSO4 | TUN_F_TSO6;
@@ -168,7 +168,7 @@ static struct vector_fds *user_init_tap_fds(struct arglist *ifspec)
 	if (fd == -1) {
 		printk(UM_KERN_ERR
 			"uml_tap: failed to create socket: %i\n", -errno);
-		goto tap_cleanup;
+		goto close_tx_fd;
 	}
 	result->rx_fd = fd;
 	memset(&ifr, 0, sizeof(ifr));
@@ -176,7 +176,7 @@ static struct vector_fds *user_init_tap_fds(struct arglist *ifspec)
 	if (ioctl(fd, SIOCGIFINDEX, (void *) &ifr) < 0) {
 		printk(UM_KERN_ERR
 			"uml_tap: failed to set interface: %i\n", -errno);
-		goto tap_cleanup;
+		goto close_rx_fd;
 	}
 
 	sock.sll_family = AF_PACKET;
@@ -188,18 +188,17 @@ static struct vector_fds *user_init_tap_fds(struct arglist *ifspec)
 		printk(UM_KERN_ERR
 			"user_init_tap: failed to bind raw pair, err %d\n",
 				-errno);
-		goto tap_cleanup;
+		goto close_rx_fd;
 	}
 	return result;
-tap_cleanup:
-	if (result != NULL) {
-		if (result->rx_fd >= 0)
-			os_close_file(result->rx_fd);
-		if (result->tx_fd >= 0)
-			os_close_file(result->tx_fd);
-		kfree(result);
-	}
 
+close_rx_fd:
+	os_close_file(result->rx_fd);
+close_tx_fd:
+	os_close_file(result->tx_fd);
+free_result:
+	kfree(result);
+report_failure:
 	printk(UM_KERN_ERR "%s: init failed: %d", __func__, err);
 	return NULL;
 }
-- 
2.16.2