string_helpers: add kstrdup_quotable

Handle allocating and escaping a string safe for logging.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: James Morris <james.l.morris@oracle.com>

diff --git a/include/linux/string_helpers.h b/include/linux/string_helpers.h
index dabe643..9de228a 100644 (file)
--- 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(const char *src, gfp_t gfp);
+
 #endif

diff --git a/lib/string_helpers.c b/lib/string_helpers.c
index 5c88204..aa00c9f 100644 (file)
--- 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(const char *src, gfp_t gfp)
+{
+       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);
+       if (!dst)
+               return NULL;
+
+       WARN_ON(string_escape_mem(src, slen, dst, dlen, flags, esc) != dlen);
+       dst[dlen] = '\0';
+
+       return dst;
+}
+EXPORT_SYMBOL_GPL(kstrdup_quotable);