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Date: Thu, 6 Apr 2017 14:18:31 -0700
From: Kees Cook <keescook@...omium.org>
To: kernel-hardening@...ts.openwall.com
Cc: Kees Cook <keescook@...omium.org>,
Michael Leibowitz <michael.leibowitz@...el.com>
Subject: [PATCH 16/18] task_struct: Allow randomized layout
This marks most of the layout of task_struct as randomizable, but leaves
thread_info and scheduler state untouched at the start, and thread_struct
untouched at the end.
Additionally, this keeps the blocked and saved sigset_t fields
unrandomized relative to each other, as found in grsecurity. I tried
to find a rationale for this, but so far I haven't been able to find
instances, but it seems like a nasty enough corner case to have to debug
that I've left it in.
One question about formatting remains: should this patch indent all the
randomized fields, due to the added anonymous struct, which would make
this patch white-space huge, or should I leave the indentation level
alone, to avoid massive churn? I opted for making the patch more
readable, but can easily do the indentation...
Signed-off-by: Kees Cook <keescook@...omium.org>
---
include/linux/sched.h | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 91f3ea399e0c..96903286b5dc 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -490,6 +490,10 @@ struct task_struct {
#endif
/* -1 unrunnable, 0 runnable, >0 stopped: */
volatile long state;
+
+ /* This begins the randomizable portion of task_struct... */
+ struct {
+
void *stack;
atomic_t usage;
/* Per task flags (PF_*), defined further below: */
@@ -745,10 +749,13 @@ struct task_struct {
/* Signal handlers: */
struct signal_struct *signal;
struct sighand_struct *sighand;
- sigset_t blocked;
sigset_t real_blocked;
- /* Restored if set_restore_sigmask() was used: */
- sigset_t saved_sigmask;
+ /* These need to stay unrandomized, relative to each other. */
+ struct {
+ sigset_t blocked;
+ /* Restored if set_restore_sigmask() was used: */
+ sigset_t saved_sigmask;
+ };
struct sigpending pending;
unsigned long sas_ss_sp;
size_t sas_ss_size;
@@ -1050,6 +1057,8 @@ struct task_struct {
#ifdef CONFIG_LIVEPATCH
int patch_state;
#endif
+ } __randomize_layout;
+
/* CPU-specific state of this task: */
struct thread_struct thread;
--
2.7.4
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