On Fri, Oct 16, 2020 at 9:26 PM Kees Cook <keescook@xxxxxxxxxxxx> wrote: > > On Fri, Oct 16, 2020 at 08:09:07PM +0200, Matteo Croce wrote: > > From: Matteo Croce <mcroce@xxxxxxxxxxxxx> > > > > 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-simple-strtoll-simple-strtoul-simple-strtoull > > -- > 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/include/linux/kernel.h?h=v5.9#n452 Cheers, -- per aspera ad upstream
