On Fri, Oct 16, 2020 at 2:20 PM Petr Mladek <pmladek@xxxxxxxx> wrote: > > On Wed 2020-10-14 23:27:46, 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, use _parse_integer() which still handles overflow, but > > restores the old behaviour of parsing until a non-digit character > > is found. > > Hmm, _parse_integer() is an internal function. And even the comment > says "Don't you dare use this function." > > I guess the it is because the base must be hardcoded. And > KSTRTOX_OVERFLOW bit must be handled. > I know, but it's the only function that I know which has the same behaviour of simple_strtoul(). Other than sscanf, which uses simple_strtoul(). I didn't know that simple_strtoul() is no longer obsolete, I will revert to it then. > 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 potentional overflow is not a big deal. The result will be > that the system will reboot on another rCPU than expected. But > it might happen also with any typo. > > > While at it, limit the CPU number to num_possible_cpus(), > > because setting it to a value lower than INT_MAX but higher > > than NR_CPUS produces the following error on reboot and shutdown: > > Great catch! Please, fix this in a separate patch. > Ok, thanks! -- per aspera ad upstream
