From: Andy Lutomirski <luto@kernel.org>
To: Yu-cheng Yu <yu-cheng.yu@intel.com>
Cc: X86 ML <x86@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
LKML <linux-kernel@vger.kernel.org>,
"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>,
linux-arch <linux-arch@vger.kernel.org>,
Linux API <linux-api@vger.kernel.org>,
Arnd Bergmann <arnd@arndb.de>,
Balbir Singh <bsingharora@gmail.com>,
Borislav Petkov <bp@alien8.de>,
Cyrill Gorcunov <gorcunov@gmail.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Eugene Syromiatnikov <esyr@redhat.com>,
Florian Weimer <fweimer@redhat.com>,
"H.J. Lu" <hjl.tools@gmail.com>, Jann Horn <jannh@google.com>,
Jonathan Corbet <corbet@lwn.net>,
Kees Cook <keescook@chromium.org>,
Mike Kravetz <mike.kravetz@oracle.com>,
Nadav Amit <nadav.amit@gmail.com>,
Oleg Nesterov <oleg@redhat.com>, Pavel Machek <pavel@ucw.cz>,
Peter Zijlstra <peterz@infradead.org>,
Randy Dunlap <rdunlap@infradead.org>,
"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
Vedvyas Shanbhogue <vedvyas.shanbhogue@intel.com>,
Dave Martin <Dave.Martin@arm.com>
Subject: Re: [RFC PATCH 3/3] Prevent user from writing to IBT bitmap.
Date: Sat, 29 Jun 2019 16:44:54 -0700 [thread overview]
Message-ID: <CALCETrXsXXJWTSJxUO8YxHUo=QJKmHyJa7iz+jOBjWMRhno4rA@mail.gmail.com> (raw)
In-Reply-To: <20190628194158.2431-3-yu-cheng.yu@intel.com>
On Fri, Jun 28, 2019 at 12:50 PM Yu-cheng Yu <yu-cheng.yu@intel.com> wrote:
>
> The IBT bitmap is visiable from user-mode, but not writable.
>
> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
>
> ---
> arch/x86/mm/fault.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
> index 59f4f66e4f2e..231196abb62e 100644
> --- a/arch/x86/mm/fault.c
> +++ b/arch/x86/mm/fault.c
> @@ -1454,6 +1454,13 @@ void do_user_addr_fault(struct pt_regs *regs,
> * we can handle it..
> */
> good_area:
> +#define USER_MODE_WRITE (FAULT_FLAG_WRITE | FAULT_FLAG_USER)
> + if (((flags & USER_MODE_WRITE) == USER_MODE_WRITE) &&
> + (vma->vm_flags & VM_IBT)) {
> + bad_area_access_error(regs, hw_error_code, address, vma);
> + return;
> + }
> +
Just make the VMA have VM_WRITE and VM_MAYWRITE clear. No new code
like this should be required.
next prev parent reply other threads:[~2019-06-29 23:45 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-28 19:41 [RFC PATCH 1/3] mm: Introduce VM_IBT for CET legacy code bitmap Yu-cheng Yu
2019-06-28 19:41 ` [RFC PATCH 2/3] Introduce arch_prctl(ARCH_X86_CET_MARK_LEGACY_CODE) Yu-cheng Yu
2019-06-29 23:43 ` Andy Lutomirski
2019-06-28 19:41 ` [RFC PATCH 3/3] Prevent user from writing to IBT bitmap Yu-cheng Yu
2019-06-29 23:44 ` Andy Lutomirski [this message]
2019-07-01 19:48 ` Yu-cheng Yu
2019-06-28 21:49 ` [RFC PATCH 1/3] mm: Introduce VM_IBT for CET legacy code bitmap Andy Lutomirski
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