Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
IronPort-SDR: TfY2BZCu06WlrN0Ey/UH/24aXYdrDOoWG064xZFZ79eIrDdOvky63XJOMgpCz+WYYue/JllW7c
 jCbnCf6H11iA==
IronPort-SDR: MzVdcs248i3MjTjkHHeBODWbsp/ohHaSFgOKTXHnytAbE8rkyOilMYMQhn6jxTB7Ul/+eFihfw
 hCmnew2PG4/A==
From:   Reinette Chatre <reinette.chatre@intel.com>
To:     tglx@linutronix.de, fenghua.yu@intel.com, bp@alien8.de,
        tony.luck@intel.com
Cc:     kuo-lang.tseng@intel.com, ravi.v.shankar@intel.com,
        mingo@redhat.com, babu.moger@amd.com, hpa@zytor.com,
        x86@kernel.org, linux-kernel@vger.kernel.org,
        Reinette Chatre <reinette.chatre@intel.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Subject: [PATCH V4 4/4] x86/resctrl: Use appropriate API for strings terminated by newline
Date:   Sat, 16 May 2020 11:28:41 -0700
Message-Id: <0c04b58148f181ba182b9a487465e4853e4eadbb.1589652468.git.reinette.chatre@intel.com>
In-Reply-To: <cover.1589652468.git.reinette.chatre@intel.com>
References: <cover.1589652468.git.reinette.chatre@intel.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

The user input to files in the resctrl filesystem are expected to be
terminated with a newline. Testing the user input includes a test for
the presence of a newline and then replacing the newline with NUL
byte followed by comparison using strcmp().

sysfs_streq() exists to test if strings are equal, treating both NUL and
newline-then-NUL as equivalent string terminations. Even more,
sysfs_match_string() exists to match a given string in an array using
sysfs_streq().

Replace existing strcmp() comparisons of strings that are terminated
with a newline with more appropriate sysfs_streq() via the
sysfs_match_string() API that can perform the match across the different
mode strings that are already maintained in an array.

Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
---
 arch/x86/kernel/cpu/resctrl/rdtgroup.c | 32 ++++++++++++++------------
 1 file changed, 17 insertions(+), 15 deletions(-)

diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 088a1536bccc..0e302d3c44e6 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -1415,12 +1415,11 @@ static ssize_t rdtgroup_mode_write(struct kernfs_open_file *of,
 {
 	struct rdtgroup *rdtgrp;
 	enum rdtgrp_mode mode;
-	int ret = 0;
+	int user_m;
+	int ret;
 
-	/* Valid input requires a trailing newline */
-	if (nbytes == 0 || buf[nbytes - 1] != '\n')
+	if (nbytes == 0)
 		return -EINVAL;
-	buf[nbytes - 1] = '\0';
 
 	rdtgrp = rdtgroup_kn_lock_live(of->kn);
 	if (!rdtgrp) {
@@ -1432,11 +1431,17 @@ static ssize_t rdtgroup_mode_write(struct kernfs_open_file *of,
 
 	mode = rdtgrp->mode;
 
-	if ((!strcmp(buf, "shareable") && mode == RDT_MODE_SHAREABLE) ||
-	    (!strcmp(buf, "exclusive") && mode == RDT_MODE_EXCLUSIVE) ||
-	    (!strcmp(buf, "pseudo-locksetup") &&
-	     mode == RDT_MODE_PSEUDO_LOCKSETUP) ||
-	    (!strcmp(buf, "pseudo-locked") && mode == RDT_MODE_PSEUDO_LOCKED))
+	ret = sysfs_match_string(rdt_mode_str, buf);
+	if (ret < 0) {
+		rdt_last_cmd_puts("Unknown or unsupported mode\n");
+		goto out;
+	}
+
+	user_m = ret;
+	ret = 0;
+
+	/* Do nothing and return success if user asks for current mode */
+	if (user_m == mode)
 		goto out;
 
 	if (mode == RDT_MODE_PSEUDO_LOCKED) {
@@ -1445,14 +1450,14 @@ static ssize_t rdtgroup_mode_write(struct kernfs_open_file *of,
 		goto out;
 	}
 
-	if (!strcmp(buf, "shareable")) {
+	if (user_m == RDT_MODE_SHAREABLE) {
 		if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKSETUP) {
 			ret = rdtgroup_locksetup_exit(rdtgrp);
 			if (ret)
 				goto out;
 		}
 		rdtgrp->mode = RDT_MODE_SHAREABLE;
-	} else if (!strcmp(buf, "exclusive")) {
+	} else if (user_m == RDT_MODE_EXCLUSIVE) {
 		if (!rdtgroup_mode_test_exclusive(rdtgrp)) {
 			ret = -EINVAL;
 			goto out;
@@ -1463,14 +1468,11 @@ static ssize_t rdtgroup_mode_write(struct kernfs_open_file *of,
 				goto out;
 		}
 		rdtgrp->mode = RDT_MODE_EXCLUSIVE;
-	} else if (!strcmp(buf, "pseudo-locksetup")) {
+	} else if (user_m == RDT_MODE_PSEUDO_LOCKSETUP) {
 		ret = rdtgroup_locksetup_enter(rdtgrp);
 		if (ret)
 			goto out;
 		rdtgrp->mode = RDT_MODE_PSEUDO_LOCKSETUP;
-	} else {
-		rdt_last_cmd_puts("Unknown or unsupported mode\n");
-		ret = -EINVAL;
 	}
 
 out:
-- 
2.21.0