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From: Kees Cook <keescook@chromium.org>
To: James Morris <jmorris@namei.org>
Cc: Kees Cook <keescook@chromium.org>, "Serge E. Hallyn" <serge@hallyn.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Kalle Valo <kvalo@codeaurora.org>,
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        Jiri Slaby <jslaby@suse.com>, Paul Moore <pmoore@redhat.com>,
        Stephen Smalley <sds@tycho.nsa.gov>,
        Mimi Zohar <zohar@linux.vnet.ibm.com>,
        Casey Schaufler <casey@schaufler-ca.com>,
        Andreas Gruenbacher <agruenba@redhat.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>,
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        Vitaly Kuznetsov <vkuznets@redhat.com>,
        linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v2 1/5] string_helpers: add kstrdup_quotable
Date: Mon, 28 Mar 2016 14:14:18 -0700
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Handle allocating and escaping a string safe for logging.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
 include/linux/string_helpers.h |  2 ++
 lib/string_helpers.c           | 28 ++++++++++++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/include/linux/string_helpers.h b/include/linux/string_helpers.h
index dabe643eb5fa..10f535bc9bb5 100644
--- a/include/linux/string_helpers.h
+++ b/include/linux/string_helpers.h
@@ -68,4 +68,6 @@ static inline int string_escape_str_any_np(const char *src, char *dst,
 	return string_escape_str(src, dst, sz, ESCAPE_ANY_NP, only);
 }
 
+char *kstrdup_quotable(char *src);
+
 #endif
diff --git a/lib/string_helpers.c b/lib/string_helpers.c
index 5c88204b6f1f..9b07c696d709 100644
--- a/lib/string_helpers.c
+++ b/lib/string_helpers.c
@@ -10,6 +10,7 @@
 #include <linux/export.h>
 #include <linux/ctype.h>
 #include <linux/errno.h>
+#include <linux/slab.h>
 #include <linux/string.h>
 #include <linux/string_helpers.h>
 
@@ -534,3 +535,30 @@ int string_escape_mem(const char *src, size_t isz, char *dst, size_t osz,
 	return p - dst;
 }
 EXPORT_SYMBOL(string_escape_mem);
+
+/*
+ * Return an allocated string that has been escaped of special characters
+ * and double quotes, making it safe to log in quotes.
+ */
+char *kstrdup_quotable(char *src)
+{
+	size_t slen, dlen;
+	char *dst;
+	const int flags = ESCAPE_HEX;
+	const char esc[] = "\f\n\r\t\v\a\e\\\"";
+
+	if (!src)
+		return NULL;
+	slen = strlen(src);
+
+	dlen = string_escape_mem(src, slen, NULL, 0, flags, esc);
+	dst = kmalloc(dlen + 1, GFP_KERNEL);
+	if (!dst)
+		return NULL;
+
+	BUG_ON(string_escape_mem(src, slen, dst, dlen, flags, esc) != dlen);
+	dst[dlen] = '\0';
+
+	return dst;
+}
+EXPORT_SYMBOL_GPL(kstrdup_quotable);
-- 
2.6.3