path: root/arch/x86
diff options
authorJann Horn <jannh@google.com>2018-08-28 20:40:33 +0200
committerThomas Gleixner <tglx@linutronix.de>2018-08-30 11:37:09 +0200
commitf12d11c5c184626b4befdee3d573ec8237405a33 (patch)
tree98e211b55e3cea0a12af6410dd21a9312eb130d4 /arch/x86
parent1f59a4581b5ecfe9b4f049a7a2cf904d8352842d (diff)
x86/entry/64: Wipe KASAN stack shadow before rewind_stack_do_exit()
Reset the KASAN shadow state of the task stack before rewinding RSP. Without this, a kernel oops will leave parts of the stack poisoned, and code running under do_exit() can trip over such poisoned regions and cause nonsensical false-positive KASAN reports about stack-out-of-bounds bugs. This does not wipe the exception stacks; if an oops happens on an exception stack, it might result in random KASAN false-positives from other tasks afterwards. This is probably relatively uninteresting, since if the kernel oopses on an exception stack, there are most likely bigger things to worry about. It'd be more interesting if vmapped stacks and KASAN were compatible, since then handle_stack_overflow() would oops from exception stack context. Fixes: 2deb4be28077 ("x86/dumpstack: When OOPSing, rewind the stack before do_exit()") Signed-off-by: Jann Horn <jannh@google.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Andrey Ryabinin <aryabinin@virtuozzo.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Alexander Potapenko <glider@google.com> Cc: Kees Cook <keescook@chromium.org> Cc: kasan-dev@googlegroups.com Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20180828184033.93712-1-jannh@google.com
Diffstat (limited to 'arch/x86')
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index 9c8652974f8e..1596e6bfea6f 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -17,6 +17,7 @@
#include <linux/bug.h>
#include <linux/nmi.h>
#include <linux/sysfs.h>
+#include <linux/kasan.h>
#include <asm/cpu_entry_area.h>
#include <asm/stacktrace.h>
@@ -346,7 +347,10 @@ void oops_end(unsigned long flags, struct pt_regs *regs, int signr)
* We're not going to return, but we might be on an IST stack or
* have very little stack space left. Rewind the stack and kill
* the task.
+ * Before we rewind the stack, we have to tell KASAN that we're going to
+ * reuse the task stack and that existing poisons are invalid.
+ kasan_unpoison_task_stack(current);