From: Kees Cook <keescook@chromium.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-kernel@vger.kernel.org,
kernel-hardening@lists.openwall.com
Subject: [PATCH] task_struct: Only use anon struct under randstruct plugin
Date: Tue, 27 Mar 2018 14:36:09 -0700 [thread overview]
Message-ID: <20180327213609.GA2964@beast> (raw)
The original intent for always adding the anonymous struct in task_struct
was to make sure we had compiler coverage. However, this caused
pathological padding of 40 bytes at the start of task_struct. Instead,
move the anonymous struct to being only used when struct layout
randomization is enabled.
Reported-by: Peter Zijlstra <peterz@infradead.org>
Fixes: 29e48ce87f1e ("task_struct: Allow randomized")
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
include/linux/compiler-clang.h | 3 ---
include/linux/compiler-gcc.h | 12 +++---------
2 files changed, 3 insertions(+), 12 deletions(-)
diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
index d3f264a5b04d..ceb96ecab96e 100644
--- a/include/linux/compiler-clang.h
+++ b/include/linux/compiler-clang.h
@@ -17,9 +17,6 @@
*/
#define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
-#define randomized_struct_fields_start struct {
-#define randomized_struct_fields_end };
-
/* all clang versions usable with the kernel support KASAN ABI version 5 */
#define KASAN_ABI_VERSION 5
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index e2c7f4369eff..b4bf73f5e38f 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -242,6 +242,9 @@
#if defined(RANDSTRUCT_PLUGIN) && !defined(__CHECKER__)
#define __randomize_layout __attribute__((randomize_layout))
#define __no_randomize_layout __attribute__((no_randomize_layout))
+/* This anon struct can add padding, so only enable it under randstruct. */
+#define randomized_struct_fields_start struct {
+#define randomized_struct_fields_end } __randomize_layout;
#endif
#endif /* GCC_VERSION >= 40500 */
@@ -256,15 +259,6 @@
*/
#define __visible __attribute__((externally_visible))
-/*
- * RANDSTRUCT_PLUGIN wants to use an anonymous struct, but it is only
- * possible since GCC 4.6. To provide as much build testing coverage
- * as possible, this is used for all GCC 4.6+ builds, and not just on
- * RANDSTRUCT_PLUGIN builds.
- */
-#define randomized_struct_fields_start struct {
-#define randomized_struct_fields_end } __randomize_layout;
-
#endif /* GCC_VERSION >= 40600 */
--
2.7.4
--
Kees Cook
Pixel Security
next reply other threads:[~2018-03-27 21:36 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-27 21:36 Kees Cook [this message]
2018-03-27 23:03 ` [PATCH] task_struct: Only use anon struct under randstruct plugin Andrew Morton
2018-03-28 0:22 ` Linus Torvalds
2018-03-28 9:51 ` Peter Zijlstra
2018-03-28 0:30 ` Kees Cook
2018-03-28 1:34 ` Andrew Morton
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20180327213609.GA2964@beast \
--to=keescook@chromium.org \
--cc=akpm@linux-foundation.org \
--cc=kernel-hardening@lists.openwall.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=peterz@infradead.org \
--cc=torvalds@linux-foundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).