Messages in this thread Patch in this message | | | Date | Sun, 11 Feb 2018 00:11:10 +0300 | From | Alexey Dobriyan <> | Subject | [PATCH] kstrtox: make kstrtobool_from_user() very strict |
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Once upon a time module parameter parsing code accepted 0, 1, y, n, Y and N for boolean values. Gratituous but contained to module code and thus tolerable.
Commit ef951599074ba4fad2d0efa0a977129b41e6d203 ("lib: move strtobool() to kstrtobool()") promoted that ugly wart to kstrtobool() and, more importantly, kstrtobool_from_user().
Later set of accepted values was expanded to "on" and "of". Now there are 6+8=14(!) valid strings for a boolean.
This patch reduces set of accepted values to "0" and "1" (with optional newline) in spirit with other kstrto*() functions.
I'm starting with kstrtobool_from_user() as it is explicitly designed to be used for interacting with userspace. Currently there are 9 users all debug code, so there is hope.
Please send before 4.16 so no real users start to depend on verbose behaviour.
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> ---
lib/kstrtox.c | 32 +++++++++++++++++++++++++++----- 1 file changed, 27 insertions(+), 5 deletions(-)
--- a/lib/kstrtox.c +++ b/lib/kstrtox.c @@ -368,19 +368,41 @@ int kstrtobool(const char *s, bool *res) EXPORT_SYMBOL(kstrtobool); /* - * Since "base" would be a nonsense argument, this open-codes the - * _from_user helper instead of using the helper macro below. + * Convert string to boolean: + * 0 => false + * 1 => true + * 0\n => false + * 1\n => true + * + * Return 0 on success or -E otherwise. */ int kstrtobool_from_user(const char __user *s, size_t count, bool *res) { - /* Longest string needed to differentiate, newline, terminator */ - char buf[4]; + /* 0|1, newline, terminator */ + char buf[3], *p; + bool val; count = min(count, sizeof(buf) - 1); if (copy_from_user(buf, s, count)) return -EFAULT; buf[count] = '\0'; - return kstrtobool(buf, res); + + p = buf; + if (*p == '0') + val = false; + else if (*p == '1') + val = true; + else + return -EINVAL; + p++; + + if (*p == '\n') + p++; + if (*p) + return -EINVAL; + + *res = val; + return 0; } EXPORT_SYMBOL(kstrtobool_from_user);
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