The patch titled
Subject: lib: harden strncpy_from_user
has been added to the -mm tree. Its filename is
lib-harden-strncpy_from_user.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/lib-harden-strncpy_from_user.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/lib-harden-strncpy_from_user.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Mark Rutland <mark.rutland@xxxxxxx>
Subject: lib: harden strncpy_from_user
The strncpy_from_user() accessor is effectively a copy_from_user()
specialised to copy strings, terminating early at a NUL byte if possible.
In other respects it is identical, and can be used to copy an arbitrarily
large buffer from userspace into the kernel. Conceptually, it exposes a
similar attack surface.
As with copy_from_user(), we check the destination range when the kernel
is built with KASAN, but unlike copy_from_user() we do not check the
destination buffer when using HARDENED_USERCOPY. As strncpy_from_user()
calls get_user() in a loop, we must call check_object_size() explicitly.
This patch adds this instrumentation to strncpy_from_user(), per the same
rationale as with the regular copy_from_user(). In the absence of
hardened usercopy this will have no impact as the instrumentation expands
to an empty static inline function.
Link: http://lkml.kernel.org/r/1472221903-31181-1-git-send-email-mark.rutland@xxxxxxx
Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/strncpy_from_user.c | 2 ++
1 file changed, 2 insertions(+)
diff -puN lib/strncpy_from_user.c~lib-harden-strncpy_from_user lib/strncpy_from_user.c
--- a/lib/strncpy_from_user.c~lib-harden-strncpy_from_user
+++ a/lib/strncpy_from_user.c
@@ -1,6 +1,7 @@
#include <linux/compiler.h>
#include <linux/export.h>
#include <linux/kasan-checks.h>
+#include <linux/thread_info.h>
#include <linux/uaccess.h>
#include <linux/kernel.h>
#include <linux/errno.h>
@@ -111,6 +112,7 @@ long strncpy_from_user(char *dst, const
long retval;
kasan_check_write(dst, count);
+ check_object_size(dst, count, false);
user_access_begin();
retval = do_strncpy_from_user(dst, src, count, max);
user_access_end();
_
Patches currently in -mm which might be from mark.rutland@xxxxxxx are
lib-harden-strncpy_from_user.patch
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
