From: Petr Mladek <pmladek@suse.com>
To: Matteo Croce <mcroce@linux.microsoft.com>
Cc: linux-kernel@vger.kernel.org, Guenter Roeck <linux@roeck-us.net>,
Arnd Bergmann <arnd@arndb.de>, Mike Rapoport <rppt@kernel.org>,
Kees Cook <keescook@chromium.org>,
Pavel Tatashin <pasha.tatashin@soleen.com>,
Robin Holt <robinmholt@gmail.com>,
Fabian Frederick <fabf@skynet.be>,
stable@vger.kernel.org
Subject: Re: [PATCH v2 2/2] reboot: fix parsing of reboot cpu number
Date: Fri, 30 Oct 2020 15:30:49 +0100 [thread overview]
Message-ID: <20201030143049.GE1602@alley> (raw)
In-Reply-To: <20201027133545.58625-3-mcroce@linux.microsoft.com>
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
next prev parent reply other threads:[~2020-10-30 14:30 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-27 13:35 [PATCH v2 0/2] fix parsing of reboot= cmdline Matteo Croce
2020-10-27 13:35 ` [PATCH v2 1/2] reboot: fix overflow parsing reboot cpu number Matteo Croce
2020-10-27 13:42 ` Greg KH
2020-10-30 14:13 ` Petr Mladek
2020-10-30 14:18 ` Matteo Croce
2020-10-27 13:35 ` [PATCH v2 2/2] reboot: fix parsing of " Matteo Croce
2020-10-27 13:42 ` Greg KH
2020-10-30 14:30 ` Petr Mladek [this message]
2020-11-01 1:57 ` Matteo Croce
2020-11-02 11:01 ` Petr Mladek
2020-11-03 11:43 ` Matteo Croce
2020-11-03 14:25 ` Petr Mladek
2020-11-03 15:43 ` Matteo Croce
2020-11-03 16:22 ` Petr Mladek
2020-10-27 13:42 ` [PATCH v2 0/2] fix parsing of reboot= cmdline Greg KH
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