On Fri, Oct 16, 2020 at 9:26 PM Kees Cook keescook@chromium.org wrote:
On Fri, Oct 16, 2020 at 08:09:07PM +0200, Matteo Croce wrote:
From: Matteo Croce mcroce@microsoft.com
The kernel cmdline reboot= argument allows to specify the CPU used for rebooting, with the syntax `s####` among the other flags, e.g.
reboot=soft,s4 reboot=warm,s31,force
In the early days the parsing was done with simple_strtoul(), later deprecated in favor of the safer kstrtoint() which handles overflow.
But kstrtoint() returns -EINVAL if there are non-digit characters in a string, so if this flag is not the last given, it's silently ignored as well as the subsequent ones.
To fix it, revert the usage of simple_strtoul(), which is no longer deprecated, and restore the old behaviour.
It is? Is there a reference, because this was never updated: https://www.kernel.org/doc/html/latest/process/deprecated.html#simple-strtol...
-- Kees Cook
Seems so, Petr Mladek replied to the previous patch:
I suggest to go back to simple_strtoul(). It is not longer obsolete. It still exists because it is needed for exactly this purpose, see the comment in include/linux/kernel.h
The comment says:
/* * Use kstrto<foo> instead. * * NOTE: simple_strto<foo> does not check for the range overflow and, * depending on the input, may give interesting results. * * Use these functions if and only if you cannot use kstrto<foo>, because * the conversion ends on the first non-digit character, which may be far * beyond the supported range. It might be useful to parse the strings like * 10x50 or 12:21 without altering original string or temporary buffer in use. * Keep in mind above caveat. */
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/incl...
Cheers,