linux-kernel - [PATCH v1] seq_file: convert mangle_path() to use string_escape

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Date:   Wed,  9 Jan 2019 17:40:22 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Alexander Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, Kees Cook <keescook@...omium.org>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: [PATCH v1] seq_file: convert mangle_path() to use string_escape_str()

Since string_escape_str() does not support overlapping buffer first we check if
there is enough room in the buffer and then update a path. The side effect of
this change is in case of failure the buffer is left unchanged.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
---
 fs/seq_file.c | 22 +++++++---------------
 1 file changed, 7 insertions(+), 15 deletions(-)

diff --git a/fs/seq_file.c b/fs/seq_file.c
index 1dea7a8a5255..b818b23070e6 100644
--- a/fs/seq_file.c
+++ b/fs/seq_file.c
@@ -421,21 +421,13 @@ EXPORT_SYMBOL(seq_printf);
  */
 char *mangle_path(char *s, const char *p, const char *esc)
 {
-	while (s <= p) {
-		char c = *p++;
-		if (!c) {
-			return s;
-		} else if (!strchr(esc, c)) {
-			*s++ = c;
-		} else if (s + 4 > p) {
-			break;
-		} else {
-			*s++ = '\\';
-			*s++ = '0' + ((c & 0300) >> 6);
-			*s++ = '0' + ((c & 070) >> 3);
-			*s++ = '0' + (c & 07);
-		}
-	}
+	size_t len = p + strlen(p) - s;
+	int ret;
+
+	ret = string_escape_str(p, NULL, 0, ESCAPE_OCTAL, esc);
+	if (ret < len)
+		return s + string_escape_str(p, s, len, ESCAPE_OCTAL, esc);
+
 	return NULL;
 }
 EXPORT_SYMBOL(mangle_path);
-- 
2.20.1