From: Yu-cheng Yu <yu-cheng.yu@intel.com>
To: x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
linux-mm@kvack.org, linux-arch@vger.kernel.org,
linux-api@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
Andy Lutomirski <luto@kernel.org>,
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>,
Dave Martin <Dave.Martin@arm.com>,
Weijiang Yang <weijiang.yang@intel.com>,
Pengfei Xu <pengfei.xu@intel.com>,
Haitao Huang <haitao.huang@intel.com>,
Rick P Edgecombe <rick.p.edgecombe@intel.com>
Cc: Yu-cheng Yu <yu-cheng.yu@intel.com>
Subject: [PATCH v28 04/10] x86/cet/ibt: Disable IBT for ia32
Date: Thu, 22 Jul 2021 13:57:17 -0700 [thread overview]
Message-ID: <20210722205723.9476-5-yu-cheng.yu@intel.com> (raw)
In-Reply-To: <20210722205723.9476-1-yu-cheng.yu@intel.com>
In a signal, a task's IBT status needs to be saved to the signal frame, and
later restored in sigreturn. For the purpose, previous versions of the
series add a new struct to the signal frame. However, a new signal frame
format (or re-using a reserved space) introduces complex compatibility
issues.
In the discussion (see link below), Andy Lutomirski proposed using a
ucontext flag. The approach is clean and eliminates most compatibility
issues.
However, a legacy IA32 signal frame does not have ucontext and cannot
support a uc flag. Thus,
- Disable IBT for ia32.
- In ia32 sigreturn, verify ibt is disabled.
Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: Florian Weimer <fweimer@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/linux-api/f6e61dae-9805-c855-8873-7481ceb7ea79@intel.com/
---
arch/x86/ia32/ia32_signal.c | 7 +++++++
arch/x86/include/asm/elf.h | 13 ++++++++++++-
2 files changed, 19 insertions(+), 1 deletion(-)
diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c
index 77d0fa90cc19..946039cb3150 100644
--- a/arch/x86/ia32/ia32_signal.c
+++ b/arch/x86/ia32/ia32_signal.c
@@ -104,6 +104,13 @@ COMPAT_SYSCALL_DEFINE0(sigreturn)
struct sigframe_ia32 __user *frame = (struct sigframe_ia32 __user *)(regs->sp-8);
sigset_t set;
+ /*
+ * Verify legacy sigreturn does not have IBT enabled.
+ */
+#ifdef CONFIG_X86_IBT
+ if (current->thread.shstk.ibt)
+ goto badframe;
+#endif
if (!access_ok(frame, sizeof(*frame)))
goto badframe;
if (__get_user(set.sig[0], &frame->sc.oldmask)
diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
index 3281a3d01bd2..cf9eeb30c00c 100644
--- a/arch/x86/include/asm/elf.h
+++ b/arch/x86/include/asm/elf.h
@@ -6,6 +6,7 @@
* ELF register definitions..
*/
#include <linux/thread_info.h>
+#include <uapi/linux/elf.h>
#include <asm/ptrace.h>
#include <asm/user.h>
@@ -403,7 +404,17 @@ struct arch_elf_state {
}
#define arch_elf_pt_proc(ehdr, phdr, elf, interp, state) (0)
-#define arch_check_elf(ehdr, interp, interp_ehdr, state) (0)
+static inline int arch_check_elf(void *ehdr, bool interp,
+ void *interp_ehdr,
+ struct arch_elf_state *state)
+{
+ /*
+ * Disable IBT for ia32
+ */
+ if (elf_check_arch_ia32((struct elf32_hdr *)ehdr))
+ state->gnu_property &= ~GNU_PROPERTY_X86_FEATURE_1_IBT;
+ return 0;
+}
/* Do not change the values. See get_align_mask() */
enum align_flags {
--
2.21.0
next prev parent reply other threads:[~2021-07-22 20:58 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-22 20:57 [PATCH v28 00/10] Control-flow Enforcement: Indirect Branch Tracking Yu-cheng Yu
2021-07-22 20:57 ` [PATCH v28 01/10] x86/cet/ibt: Add Kconfig option for " Yu-cheng Yu
2021-07-22 20:57 ` [PATCH v28 02/10] x86/cet/ibt: Add user-mode Indirect Branch Tracking support Yu-cheng Yu
2021-07-22 20:57 ` [PATCH v28 03/10] x86/cet/ibt: Handle signals for Indirect Branch Tracking Yu-cheng Yu
2021-07-22 20:57 ` Yu-cheng Yu [this message]
2021-08-09 23:04 ` [PATCH v28 04/10] x86/cet/ibt: Disable IBT for ia32 Andy Lutomirski
2021-08-10 16:07 ` Yu, Yu-cheng
2021-07-22 20:57 ` [PATCH v28 05/10] x86/cet/ibt: Update ELF header parsing for Indirect Branch Tracking Yu-cheng Yu
2021-07-22 20:57 ` [PATCH v28 06/10] x86/cet/ibt: Update arch_prctl functions " Yu-cheng Yu
2021-07-22 20:57 ` [PATCH v28 07/10] x86/vdso: Insert endbr32/endbr64 to vDSO Yu-cheng Yu
2021-07-22 20:57 ` [PATCH v28 08/10] x86/vdso: Introduce ENDBR macro Yu-cheng Yu
2021-07-22 20:57 ` [PATCH v28 09/10] x86/vdso/32: Add ENDBR to __kernel_vsyscall entry point Yu-cheng Yu
2021-07-22 20:57 ` [PATCH v28 10/10] x86/vdso: Add ENDBR to __vdso_sgx_enter_enclave Yu-cheng Yu
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