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Date: Fri, 22 Jan 2016 15:29:45 -0800
From: Kees Cook <keescook@...omium.org>
To: Joe Perches <joe@...ches.com>
Cc: Ingo Molnar <mingo@...hat.com>, Rasmus Villemoes <linux@...musvillemoes.dk>,
Daniel Borkmann <daniel@...earbox.net>, Andy Lutomirski <luto@...capital.net>,
"H. Peter Anvin" <hpa@...or.com>, Michael Ellerman <mpe@...erman.id.au>,
Mathias Krause <minipli@...glemail.com>, Thomas Gleixner <tglx@...utronix.de>,
"x86@...nel.org" <x86@...nel.org>, Arnd Bergmann <arnd@...db.de>, PaX Team <pageexec@...email.hu>,
Emese Revfy <re.emese@...il.com>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, LKML <linux-kernel@...r.kernel.org>,
linux-arch <linux-arch@...r.kernel.org>
Subject: Re: [PATCH v4 2/8] lib: add "on" and "off" to strtobool
On Tue, Jan 19, 2016 at 6:09 PM, Joe Perches <joe@...ches.com> wrote:
> On Tue, 2016-01-19 at 10:08 -0800, Kees Cook wrote:
>> Several places in the kernel expect to use "on" and "off" for their
>> boolean signifiers, so add them to strtobool.
>
> Several places in the kernel use a char address like
> fs/cifs/cifs_debug.c
>
>
> char c;
> ...
>
>
> if (strtobool(&c, ...))
>
> Using s[1] might cause problems for those uses.
Oh ew. Thanks for noticing that.
>> diff --git a/lib/string.c b/lib/string.c
> []
>> @@ -635,12 +635,15 @@ EXPORT_SYMBOL(sysfs_streq);
>> * @s: input string
>> * @res: result
>> *
>> - * This routine returns 0 iff the first character is one of 'Yy1Nn0'.
>> - * Otherwise it will return -EINVAL. Value pointed to by res is
>> - * updated upon finding a match.
>> + * This routine returns 0 iff the first character is one of 'Yy1Nn0', or
>> + * [oO][NnFf] for "on" and "off". Otherwise it will return -EINVAL. Value
>> + * pointed to by res is updated upon finding a match.
>> */
>> int strtobool(const char *s, bool *res)
>> {
>> + if (!s)
>> + return -EINVAL;
>> +
>> switch (s[0]) {
>> case 'y':
>> case 'Y':
>> @@ -652,6 +655,21 @@ int strtobool(const char *s, bool *res)
>> case '0':
>> *res = false;
>> break;
>> + case 'o':
>> + case 'O':
>> + switch (s[1]) {
>> + case 'n':
>> + case 'N':
>> + *res = true;
>> + break;
>> + case 'f':
>> + case 'F':
>
> Perhaps
> switch (tolower(s[1])) {
> is more readable
I opted to let the compiler deal with optimizing this, and I left the
switch statement as close to original as possible.
-Kees
>
>> + *res = false;
>> + break;
>> + default:
>> + return -EINVAL;
>> + }
>> + break;
>
> or maybe /* fallthrough */
>
>> default:
>> return -EINVAL;
>> }
>
--
Kees Cook
Chrome OS & Brillo Security
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