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Date: Mon, 3 Sep 2018 18:56:55 +0200 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Jann Horn <jannh@...gle.com>, Thomas Gleixner <tglx@...utronix.de>, Andrey Ryabinin <aryabinin@...tuozzo.com>, Andy Lutomirski <luto@...nel.org>, Dmitry Vyukov <dvyukov@...gle.com>, Alexander Potapenko <glider@...gle.com>, Kees Cook <keescook@...omium.org>, kasan-dev@...glegroups.com Subject: [PATCH 4.9 091/107] x86/entry/64: Wipe KASAN stack shadow before rewind_stack_do_exit() 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jann Horn <jannh@...gle.com> commit f12d11c5c184626b4befdee3d573ec8237405a33 upstream. 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@...gle.com> Signed-off-by: Thomas Gleixner <tglx@...utronix.de> Acked-by: Andrey Ryabinin <aryabinin@...tuozzo.com> Cc: Andy Lutomirski <luto@...nel.org> Cc: Dmitry Vyukov <dvyukov@...gle.com> Cc: Alexander Potapenko <glider@...gle.com> Cc: Kees Cook <keescook@...omium.org> Cc: kasan-dev@...glegroups.com Cc: stable@...r.kernel.org Link: https://lkml.kernel.org/r/20180828184033.93712-1-jannh@google.com Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- arch/x86/kernel/dumpstack.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/arch/x86/kernel/dumpstack.c +++ b/arch/x86/kernel/dumpstack.c @@ -15,6 +15,7 @@ #include <linux/bug.h> #include <linux/nmi.h> #include <linux/sysfs.h> +#include <linux/kasan.h> #include <asm/stacktrace.h> #include <asm/unwind.h> @@ -229,7 +230,10 @@ void oops_end(unsigned long flags, struc * 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); rewind_stack_do_exit(signr); } NOKPROBE_SYMBOL(oops_end);
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