linux-kernel - [PATCH 3/6] string_helpers: add kstrdup_quotable

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Message-Id: <1461192388-13900-4-git-send-email-keescook@chromium.org>
Date:	Wed, 20 Apr 2016 15:46:25 -0700
From:	Kees Cook <keescook@...omium.org>
To:	James Morris <jmorris@...ei.org>
Cc:	Kees Cook <keescook@...omium.org>,
	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	Joe Perches <joe@...ches.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	Jonathan Corbet <corbet@....net>,
	Kalle Valo <kvalo@...eaurora.org>,
	Mauro Carvalho Chehab <mchehab@....samsung.com>,
	Guenter Roeck <linux@...ck-us.net>,
	Jiri Slaby <jslaby@...e.com>, Paul Moore <pmoore@...hat.com>,
	Stephen Smalley <sds@...ho.nsa.gov>,
	Casey Schaufler <casey@...aufler-ca.com>,
	Andreas Gruenbacher <agruenba@...hat.com>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Vitaly Kuznetsov <vkuznets@...hat.com>,
	linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org
Subject: [PATCH 3/6] string_helpers: add kstrdup_quotable_file

Allocate a NULL-terminated file path with special characters escaped,
safe for logging.

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 include/linux/string_helpers.h |  3 +++
 lib/string_helpers.c           | 30 ++++++++++++++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/include/linux/string_helpers.h b/include/linux/string_helpers.h
index 684d2695fc36..5ce9538f290e 100644
--- a/include/linux/string_helpers.h
+++ b/include/linux/string_helpers.h
@@ -3,6 +3,8 @@
 
 #include <linux/types.h>
 
+struct file;
+
 /* Descriptions of the types of units to
  * print in */
 enum string_size_units {
@@ -70,5 +72,6 @@ static inline int string_escape_str_any_np(const char *src, char *dst,
 
 char *kstrdup_quotable(const char *src, gfp_t gfp);
 char *kstrdup_quotable_cmdline(struct task_struct *task, gfp_t gfp);
+char *kstrdup_quotable_file(struct file *file, gfp_t gfp);
 
 #endif
diff --git a/lib/string_helpers.c b/lib/string_helpers.c
index b16ee85aaf87..ecaac2c0526f 100644
--- a/lib/string_helpers.c
+++ b/lib/string_helpers.c
@@ -10,6 +10,8 @@
 #include <linux/export.h>
 #include <linux/ctype.h>
 #include <linux/errno.h>
+#include <linux/fs.h>
+#include <linux/limits.h>
 #include <linux/mm.h>
 #include <linux/slab.h>
 #include <linux/string.h>
@@ -596,3 +598,31 @@ char *kstrdup_quotable_cmdline(struct task_struct *task, gfp_t gfp)
 	return quoted;
 }
 EXPORT_SYMBOL_GPL(kstrdup_quotable_cmdline);
+
+/*
+ * Returns allocated NULL-terminated string containing pathname,
+ * with special characters escaped, able to be safely logged. If
+ * there is an error, the leading character will be "<".
+ */
+char *kstrdup_quotable_file(struct file *file, gfp_t gfp)
+{
+	char *temp, *pathname;
+
+	if (!file)
+		return kstrdup("<unknown>", gfp);
+
+	/* We add 11 spaces for ' (deleted)' to be appended */
+	temp = kmalloc(PATH_MAX + 11, GFP_TEMPORARY);
+	if (!temp)
+		return kstrdup("<no_memory>", gfp);
+
+	pathname = file_path(file, temp, PATH_MAX + 11);
+	if (IS_ERR(pathname))
+		pathname = kstrdup("<too_long>", gfp);
+	else
+		pathname = kstrdup_quotable(pathname, gfp);
+
+	kfree(temp);
+	return pathname;
+}
+EXPORT_SYMBOL_GPL(kstrdup_quotable_file);
-- 
2.6.3