mm/usercopy: return 1 from hardened_usercopy __setup() handler

stable inclusion
from stable-v5.10.110
commit 86489492e87680c9c1c13a1a73ee278c13ecbab6
bugzilla: https://gitee.com/openeuler/kernel/issues/I574AL

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=86489492e87680c9c1c13a1a73ee278c13ecbab6

--------------------------------

commit 05fe3c10 upstream.

__setup() handlers should return 1 if the command line option is handled
and 0 if not (or maybe never return 0; it just pollutes init's
environment).  This prevents:

  Unknown kernel command line parameters \
  "BOOT_IMAGE=/boot/bzImage-517rc5 hardened_usercopy=off", will be \
  passed to user space.

  Run /sbin/init as init process
   with arguments:
     /sbin/init
   with environment:
     HOME=/
     TERM=linux
     BOOT_IMAGE=/boot/bzImage-517rc5
     hardened_usercopy=off
or
     hardened_usercopy=on
but when "hardened_usercopy=foo" is used, there is no Unknown kernel
command line parameter.

Return 1 to indicate that the boot option has been handled.
Print a warning if strtobool() returns an error on the option string,
but do not mark this as in unknown command line option and do not cause
init's environment to be polluted with this string.

Link: https://lkml.kernel.org/r/20220222034249.14795-1-rdunlap@infradead.org
Link: lore.kernel.org/r/64644a2f-4a20-bab3-1e15-3b2cdd0defe3@omprussia.ru
Fixes: b5cb15d9 ("usercopy: Allow boot cmdline disabling of hardening")
Signed-off-by: NRandy Dunlap <rdunlap@infradead.org>
Reported-by: NIgor Zhbanov <i.zhbanov@omprussia.ru>
Acked-by: NChris von Recklinghausen <crecklin@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NYu Liao <liaoyu15@huawei.com>
Reviewed-by: NWei Li <liwei391@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

mm/usercopy.c

@@ -296,7 +296,10 @@ static bool enable_checks __initdata = true;
 
 static int __init parse_hardened_usercopy(char *str)
 {
-	return strtobool(str, &enable_checks);
+	if (strtobool(str, &enable_checks))
+		pr_warn("Invalid option string for hardened_usercopy: '%s'\n",
+			str);
+	return 1;
 }
 
 __setup("hardened_usercopy=", parse_hardened_usercopy);