Messages in this thread | | | Date | Fri, 16 Oct 2020 14:20:39 +0200 | From | Petr Mladek <> | Subject | Re: [PATCH] reboot: fix parsing of reboot cpu number |
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On Wed 2020-10-14 23:27:46, 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, 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 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.
Best Regards, Petr
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