linux-kernel - [PATCH] arch/arm/l2x0: Use sysfs_emit() in show() callback function

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Date:   Fri, 17 Feb 2023 22:40:49 +0530
From:   Deepak R Varma <drv@...lo.com>
To:     Russell King <linux@...linux.org.uk>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     Saurabh Singh Sengar <ssengar@...rosoft.com>,
        Praveen Kumar <kumarpraveen@...ux.microsoft.com>,
        Deepak R Varma <drv@...lo.com>
Subject: [PATCH] arch/arm/l2x0: Use sysfs_emit() in show() callback function

Using sprintf/snprintf functions are error prone and suggested to be
replaced by scnprintf/vscnrptintf as outlined in this [1] LWN article.

A more recent recommendation is to use sysfs_emit() or sysfs_emit_at()
as per Documentation/filesystems/sysfs.rst in show() callback function
when formatting values to be returned to user-space. These helper
functions are PAGE_SIZE aware and wrap a safer call to vscnprintf().

[1] https://lwn.net/Articles/69419/

Issue identified using the coccinelle device_attr_show.cocci script.

Signed-off-by: Deepak R Varma <drv@...lo.com>
---
Please note:
   1. Change compile tested using sama7_defconfig
   2. The driver name in the patch subject is best derived out of the 5 unique
      names available for the current committed patches. If this is incorrect,
      please suggest what it should be set to.


 arch/arm/mm/cache-l2x0-pmu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/mm/cache-l2x0-pmu.c b/arch/arm/mm/cache-l2x0-pmu.c
index 993fefdc167a..a9bd05b82003 100644
--- a/arch/arm/mm/cache-l2x0-pmu.c
+++ b/arch/arm/mm/cache-l2x0-pmu.c
@@ -343,7 +343,7 @@ static ssize_t l2x0_pmu_event_show(struct device *dev,
 	struct l2x0_event_attribute *lattr;
 
 	lattr = container_of(attr, typeof(*lattr), attr);
-	return snprintf(buf, PAGE_SIZE, "config=0x%x\n", lattr->config);
+	return sysfs_emit(buf, "config=0x%x\n", lattr->config);
 }
 
 static umode_t l2x0_pmu_event_attr_is_visible(struct kobject *kobj,
-- 
2.34.1