On Wed, 9 Jan 2019 17:40:22 +0200 Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> wrote:
> 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.
>
> ...
>
> --- 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);
Confusing.
I think the objective of the patch is to use an existing library
function rather than open-coding, but the library function doesn't
support in-place operation on the string. So the old mangle_path() was
OK with in-place conversion, but the new mangle_path() is not. Is that
correct? Do we know that all existing mangle_path() callers are OK
with this? Please make all this clear in the changelog.
Also, the identifier `ret' is widely understood to mean "the value
which this function will return", but that is not the case here.
Please use a more appropriate identifier.
