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

2 files changed, 33 insertions, 0 deletions

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);