[PATCH 5.16 0974/1017] mm/usercopy: return 1 from hardened_usercopy __setup() handler

Greg Kroah-Hartman
2022-04-05T10:28:40Z

From: Randy Dunlap <rdunlap@infradead.org>

commit 05fe3c103f7e6b8b4fca8a7001dfc9ed4628085b 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: b5cb15d9372ab ("usercopy: Allow boot cmdline disabling of hardening")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reported-by: Igor Zhbanov <i.zhbanov@omprussia.ru>
Acked-by: Chris von Recklinghausen <crecklin@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
mm/usercopy.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

--- a/mm/usercopy.c
+++ b/mm/usercopy.c
@@ -294,7 +294,10 @@ static bool enable_checks __initdata = t

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);