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 e7b78d5..8fbba43 100644 (file)
--- 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;