linux-kernel - [PATCH] perf/x86/amd/core: Use sysfs_emit() in show() callback function

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Date:   Fri, 17 Feb 2023 22:12:57 +0530
From:   Deepak R Varma <drv@...lo.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, linux-perf-users@...r.kernel.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] perf/x86/amd/core: 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>
---
 arch/x86/events/amd/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/events/amd/core.c b/arch/x86/events/amd/core.c
index 4386b10682ce..47a3a841332a 100644
--- a/arch/x86/events/amd/core.c
+++ b/arch/x86/events/amd/core.c
@@ -1272,7 +1272,7 @@ static ssize_t branches_show(struct device *cdev,
 			      struct device_attribute *attr,
 			      char *buf)
 {
-	return snprintf(buf, PAGE_SIZE, "%d\n", x86_pmu.lbr_nr);
+	return sysfs_emit(buf, "%d\n", x86_pmu.lbr_nr);
 }
 
 static DEVICE_ATTR_RO(branches);
-- 
2.34.1