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.
Hmm, I suggest to split this into 3 patches and switch the order:
+ 1st patch should simply revert the commit 616feab75397 ("kernel/reboot.c: convert simple_strtoul to kstrtoint").
+ 2nd patch should merge the two branches without any functional change.
+ 3rd patch should add the check for num_possible_cpus() and update the value only when it is valid.
I am sorry that I did not suggested this when reviewed v1. I have missed this functional change at that time.
Best Regards, Petr