Messages in this thread | | | Date | Mon, 2 Nov 2020 12:01:07 +0100 | From | Petr Mladek <> | Subject | Re: [PATCH v2 2/2] reboot: fix parsing of reboot cpu number |
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On Sun 2020-11-01 02:57:40, Matteo Croce wrote: > On Fri, Oct 30, 2020 at 3:30 PM Petr Mladek <pmladek@suse.com> wrote: > > > > On Tue 2020-10-27 14:35:45, 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. > > > > > > While at it, merge two identical code blocks into one. > > > > > --- a/kernel/reboot.c > > > +++ b/kernel/reboot.c > > > @@ -552,25 +552,19 @@ static int __init reboot_setup(char *str) > > > > > > case 's': > > > { > > > - int rc; > > > - > > > - if (isdigit(*(str+1))) { > > > - rc = kstrtoint(str+1, 0, &reboot_cpu); > > > - if (rc) > > > - return rc; > > > - if (reboot_cpu >= num_possible_cpus()) { > > > - reboot_cpu = 0; > > > - return -ERANGE; > > > - } > > > - } else if (str[1] == 'm' && str[2] == 'p' && > > > - isdigit(*(str+3))) { > > > - rc = kstrtoint(str+3, 0, &reboot_cpu); > > > - if (rc) > > > - return rc; > > > - if (reboot_cpu >= num_possible_cpus()) { > > > - reboot_cpu = 0; > > > > ^^^^^^ > > > > > + int cpu; > > > + > > > + /* > > > + * reboot_cpu is s[mp]#### with #### being the processor > > > + * to be used for rebooting. Skip 's' or 'smp' prefix. > > > + */ > > > + str += str[1] == 'm' && str[2] == 'p' ? 3 : 1; > > > + > > > + if (isdigit(str[0])) { > > > + cpu = simple_strtoul(str, NULL, 0); > > > + if (cpu >= num_possible_cpus()) > > > return -ERANGE; > > > - } > > > + reboot_cpu = cpu; > > > > The original value stays when the new one is out of range. It is > > small functional change that should get mentioned in the commit > > message or better fixed separately.
Ah, I see. From some reason, I assumed that it was defined as module_param() or core_param(). Then it would be possible to modify it later via /sys.
I am sorry for the noise.
Best Regards, Petr
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