Messages in this thread | | | Date | Fri, 5 Nov 2021 09:58:47 -0700 | Subject | Re: [PATCH] landlock: Initialize kernel stack variables properly | From | J Freyensee <> |
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On 11/4/21 4:41 AM, Austin Kim wrote: > 2021년 11월 3일 (수) 오후 9:14, Mickaël Salaün <mic@digikod.net>님이 작성: >> Hi Austin, >> >> On 03/11/2021 08:14, Austin Kim wrote: >>> In case kernel stack variables are not initialized properly, there might >>> be a little chance of kernel information disclosure. So it is better for >>> kernel stack variables to be initialized with null characters. >>> >>> Signed-off-by: Austin Kim <austindh.kim@gmail.com> >>> --- >>> security/landlock/syscalls.c | 2 ++ >>> 1 file changed, 2 insertions(+) >>> >>> diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c >>> index 32396962f04d..50a6f7091428 100644 >>> --- a/security/landlock/syscalls.c >>> +++ b/security/landlock/syscalls.c >>> @@ -320,6 +320,8 @@ SYSCALL_DEFINE4(landlock_add_rule, >>> if (rule_type != LANDLOCK_RULE_PATH_BENEATH) >>> return -EINVAL; >>> >>> + memset(&path_beneath_attr, 0, sizeof(path_beneath_attr)); >>> + >> This memset is already done with the copy_from_user() call just below. >> > It seems that memset() is done inside copy_from_user(). > Thanks for feedback.
If you are really sensitive of what information may be disclosed in this case you can consider memzero_explicit() to use instead:
https://www.kernel.org/doc/htmldocs/kernel-api/API-memzero-explicit.html
Jay
> > BR, > Austin Kim > >>> /* Copies raw user space buffer, only one type for now. */ >>> res = copy_from_user(&path_beneath_attr, rule_attr, >>> sizeof(path_beneath_attr)); >>>
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