The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 8b92c4ff4423aa9900cf838d3294fcade4dbda35 Mon Sep 17 00:00:00 2001

From: Matteo Croce mcroce@microsoft.com Date: Fri, 13 Nov 2020 22:52:02 -0800 Subject: [PATCH] Revert "kernel/reboot.c: convert simple_strtoul to kstrtoint"

Patch series "fix parsing of reboot= cmdline", v3.

The parsing of the reboot= cmdline has two major errors:

- a missing bound check can crash the system on reboot

- parsing of the cpu number only works if specified last

Fix both.

This patch (of 2):

This reverts commit 616feab753972b97.

kstrtoint() and simple_strtoul() have a subtle difference which makes them non interchangeable: if a non digit character is found amid the parsing, the former will return an error, while the latter will just stop parsing, e.g. simple_strtoul("123xyx") = 123.

The kernel cmdline reboot= argument allows to specify the CPU used for rebooting, with the syntax `s####` among the other flags, e.g. "reboot=warm,s31,force", so if this flag is not the last given, it's silently ignored as well as the subsequent ones.

Fixes: 616feab75397 ("kernel/reboot.c: convert simple_strtoul to kstrtoint") Signed-off-by: Matteo Croce mcroce@microsoft.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Cc: Guenter Roeck linux@roeck-us.net Cc: Petr Mladek pmladek@suse.com Cc: Arnd Bergmann arnd@arndb.de Cc: Mike Rapoport rppt@kernel.org Cc: Kees Cook keescook@chromium.org Cc: Pavel Tatashin pasha.tatashin@soleen.com Cc: Robin Holt robinmholt@gmail.com Cc: Fabian Frederick fabf@skynet.be Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20201103214025.116799-2-mcroce@linux.microsoft.com Signed-off-by: Linus Torvalds torvalds@linux-foundation.org

diff --git a/kernel/reboot.c b/kernel/reboot.c index e7b78d5ae1ab..8fbba433725e 100644 --- a/kernel/reboot.c +++ b/kernel/reboot.c @@ -551,22 +551,15 @@ static int __init reboot_setup(char *str) break;

case 's': - { - int rc; - - if (isdigit(*(str+1))) { - rc = kstrtoint(str+1, 0, &reboot_cpu); - if (rc) - return rc; - } else if (str[1] == 'm' && str[2] == 'p' && - isdigit(*(str+3))) { - rc = kstrtoint(str+3, 0, &reboot_cpu); - if (rc) - return rc; - } else + if (isdigit(*(str+1))) + reboot_cpu = simple_strtoul(str+1, NULL, 0); + else if (str[1] == 'm' && str[2] == 'p' && + isdigit(*(str+3))) + reboot_cpu = simple_strtoul(str+3, NULL, 0); + else *mode = REBOOT_SOFT; break; - } + case 'g': *mode = REBOOT_GPIO; break;