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>,
Vedvyas Shanbhogue <vedvyas.shanbhogue@intel.com>,
Dave Martin <Dave.Martin@arm.com>,
Weijiang Yang <weijiang.yang@intel.com>,
Pengfei Xu <pengfei.xu@intel.com>
Cc: Yu-cheng Yu <yu-cheng.yu@intel.com>
Subject: [PATCH v19 23/25] x86/cet/shstk: Handle thread shadow stack
Date: Wed, 3 Feb 2021 14:55:45 -0800 [thread overview]
Message-ID: <20210203225547.32221-24-yu-cheng.yu@intel.com> (raw)
In-Reply-To: <20210203225547.32221-1-yu-cheng.yu@intel.com>
The kernel allocates (and frees on thread exit) a new shadow stack for a
pthread child.
It is possible for the kernel to complete the clone syscall and set the
child's shadow stack pointer to NULL and let the child thread allocate
a shadow stack for itself. There are two issues in this approach: It
is not compatible with existing code that does inline syscall and it
cannot handle signals before the child can successfully allocate a
shadow stack.
A 64-bit shadow stack has a size of min(RLIMIT_STACK, 4 GB). A compat-mode
thread shadow stack has a size of 1/4 min(RLIMIT_STACK, 4 GB). This allows
more threads to run in a 32-bit address space.
Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
---
arch/x86/include/asm/cet.h | 3 ++
arch/x86/include/asm/mmu_context.h | 3 ++
arch/x86/kernel/cet.c | 44 ++++++++++++++++++++++++++++++
arch/x86/kernel/process.c | 8 ++++++
4 files changed, 58 insertions(+)
diff --git a/arch/x86/include/asm/cet.h b/arch/x86/include/asm/cet.h
index 73435856ce54..ec4b5e62d0ce 100644
--- a/arch/x86/include/asm/cet.h
+++ b/arch/x86/include/asm/cet.h
@@ -18,12 +18,15 @@ struct cet_status {
#ifdef CONFIG_X86_CET
int cet_setup_shstk(void);
+int cet_setup_thread_shstk(struct task_struct *p, unsigned long clone_flags);
void cet_disable_shstk(void);
void cet_free_shstk(struct task_struct *p);
int cet_verify_rstor_token(bool ia32, unsigned long ssp, unsigned long *new_ssp);
void cet_restore_signal(struct sc_ext *sc);
int cet_setup_signal(bool ia32, unsigned long rstor, struct sc_ext *sc);
#else
+static inline int cet_setup_thread_shstk(struct task_struct *p,
+ unsigned long clone_flags) { return 0; }
static inline void cet_disable_shstk(void) {}
static inline void cet_free_shstk(struct task_struct *p) {}
static inline void cet_restore_signal(struct sc_ext *sc) { return; }
diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h
index 27516046117a..e90bd2ee8498 100644
--- a/arch/x86/include/asm/mmu_context.h
+++ b/arch/x86/include/asm/mmu_context.h
@@ -11,6 +11,7 @@
#include <asm/tlbflush.h>
#include <asm/paravirt.h>
+#include <asm/cet.h>
#include <asm/debugreg.h>
extern atomic64_t last_mm_ctx_id;
@@ -146,6 +147,8 @@ do { \
#else
#define deactivate_mm(tsk, mm) \
do { \
+ if (!tsk->vfork_done) \
+ cet_free_shstk(tsk); \
load_gs_index(0); \
loadsegment(fs, 0); \
} while (0)
diff --git a/arch/x86/kernel/cet.c b/arch/x86/kernel/cet.c
index c3da4f59bd17..feb466dc2ea8 100644
--- a/arch/x86/kernel/cet.c
+++ b/arch/x86/kernel/cet.c
@@ -172,6 +172,50 @@ int cet_setup_shstk(void)
return 0;
}
+int cet_setup_thread_shstk(struct task_struct *tsk, unsigned long clone_flags)
+{
+ unsigned long addr, size;
+ struct cet_user_state *state;
+ struct cet_status *cet = &tsk->thread.cet;
+
+ if (!cet->shstk_size)
+ return 0;
+
+ if ((clone_flags & (CLONE_VFORK | CLONE_VM)) != CLONE_VM)
+ return 0;
+
+ state = get_xsave_addr(&tsk->thread.fpu.state.xsave,
+ XFEATURE_CET_USER);
+
+ if (!state)
+ return -EINVAL;
+
+ /* Cap shadow stack size to 4 GB */
+ size = min(rlimit(RLIMIT_STACK), 1UL << 32);
+
+ /*
+ * Compat-mode pthreads share a limited address space.
+ * If each function call takes an average of four slots
+ * stack space, allocate 1/4 of stack size for shadow stack.
+ */
+ if (in_compat_syscall())
+ size /= 4;
+ size = round_up(size, PAGE_SIZE);
+ addr = alloc_shstk(size, 0);
+
+ if (IS_ERR_VALUE(addr)) {
+ cet->shstk_base = 0;
+ cet->shstk_size = 0;
+ return PTR_ERR((void *)addr);
+ }
+
+ fpu__prepare_write(&tsk->thread.fpu);
+ state->user_ssp = (u64)(addr + size);
+ cet->shstk_base = addr;
+ cet->shstk_size = size;
+ return 0;
+}
+
void cet_disable_shstk(void)
{
struct cet_status *cet = ¤t->thread.cet;
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 145a7ac0c19a..3af6b36e1a5c 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -43,6 +43,7 @@
#include <asm/io_bitmap.h>
#include <asm/proto.h>
#include <asm/frame.h>
+#include <asm/cet.h>
#include "process.h"
@@ -109,6 +110,7 @@ void exit_thread(struct task_struct *tsk)
free_vm86(t);
+ cet_free_shstk(tsk);
fpu__drop(fpu);
}
@@ -181,6 +183,12 @@ int copy_thread(unsigned long clone_flags, unsigned long sp, unsigned long arg,
if (clone_flags & CLONE_SETTLS)
ret = set_new_tls(p, tls);
+#ifdef CONFIG_X86_64
+ /* Allocate a new shadow stack for pthread */
+ if (!ret)
+ ret = cet_setup_thread_shstk(p, clone_flags);
+#endif
+
if (!ret && unlikely(test_tsk_thread_flag(current, TIF_IO_BITMAP)))
io_bitmap_share(p);
--
2.21.0
next prev parent reply other threads:[~2021-02-03 23:14 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-03 22:55 [PATCH v19 00/25] Control-flow Enforcement: Shadow Stack Yu-cheng Yu
2021-02-03 22:55 ` [PATCH v19 01/25] Documentation/x86: Add CET description Yu-cheng Yu
2021-02-04 19:52 ` Kees Cook
2021-02-04 20:03 ` Yu, Yu-cheng
2021-02-03 22:55 ` [PATCH v19 02/25] x86/cet/shstk: Add Kconfig option for user-mode control-flow protection Yu-cheng Yu
2021-02-04 19:56 ` Kees Cook
2021-02-05 0:05 ` Yu, Yu-cheng
2021-02-03 22:55 ` [PATCH v19 03/25] x86/cpufeatures: Add CET CPU feature flags for Control-flow Enforcement Technology (CET) Yu-cheng Yu
2021-02-04 19:57 ` Kees Cook
2021-02-03 22:55 ` [PATCH v19 04/25] x86/cpufeatures: Introduce X86_FEATURE_CET and setup functions Yu-cheng Yu
2021-02-04 19:58 ` Kees Cook
2021-02-05 13:43 ` Borislav Petkov
2021-02-05 16:15 ` Yu, Yu-cheng
2021-02-03 22:55 ` [PATCH v19 05/25] x86/fpu/xstate: Introduce CET MSR and XSAVES supervisor states Yu-cheng Yu
2021-02-04 19:59 ` Kees Cook
2021-02-03 22:55 ` [PATCH v19 06/25] x86/cet: Add control-protection fault handler Yu-cheng Yu
2021-02-04 20:09 ` Kees Cook
2021-02-05 0:10 ` Yu, Yu-cheng
2021-02-05 13:59 ` Borislav Petkov
2021-02-05 18:00 ` Yu, Yu-cheng
2021-02-05 18:29 ` Kees Cook
2021-02-08 18:20 ` Borislav Petkov
2021-02-08 18:50 ` Yu, Yu-cheng
2021-02-08 18:53 ` Borislav Petkov
2021-02-08 19:23 ` Yu, Yu-cheng
2021-02-08 19:48 ` Borislav Petkov
2021-02-08 20:11 ` Yu, Yu-cheng
2021-02-03 22:55 ` [PATCH v19 07/25] x86/mm: Remove _PAGE_DIRTY from kernel RO pages Yu-cheng Yu
2021-02-04 20:10 ` Kees Cook
2021-02-03 22:55 ` [PATCH v19 08/25] x86/mm: Introduce _PAGE_COW Yu-cheng Yu
2021-02-04 20:19 ` Kees Cook
2021-02-04 20:27 ` Dave Hansen
2021-02-05 18:41 ` Yu, Yu-cheng
2021-02-08 23:03 ` Yu, Yu-cheng
2021-02-05 18:58 ` Yu, Yu-cheng
2021-02-03 22:55 ` [PATCH v19 09/25] drm/i915/gvt: Change _PAGE_DIRTY to _PAGE_DIRTY_BITS Yu-cheng Yu
2021-02-03 22:55 ` [PATCH v19 10/25] x86/mm: Update pte_modify for _PAGE_COW Yu-cheng Yu
2021-02-04 20:20 ` Kees Cook
2021-02-03 22:55 ` [PATCH v19 11/25] x86/mm: Update ptep_set_wrprotect() and pmdp_set_wrprotect() for transition from _PAGE_DIRTY to _PAGE_COW Yu-cheng Yu
2021-02-04 20:21 ` Kees Cook
2021-02-03 22:55 ` [PATCH v19 12/25] mm: Introduce VM_SHSTK for shadow stack memory Yu-cheng Yu
2021-02-04 20:46 ` Cyrill Gorcunov
2021-02-04 21:48 ` Yu, Yu-cheng
2021-02-03 22:55 ` [PATCH v19 13/25] x86/mm: Shadow Stack page fault error checking Yu-cheng Yu
2021-02-03 22:55 ` [PATCH v19 14/25] x86/mm: Update maybe_mkwrite() for shadow stack Yu-cheng Yu
2021-02-04 20:22 ` Kees Cook
2021-02-03 22:55 ` [PATCH v19 15/25] mm: Fixup places that call pte_mkwrite() directly Yu-cheng Yu
2021-02-04 20:22 ` Kees Cook
2021-02-03 22:55 ` [PATCH v19 16/25] mm: Add guard pages around a shadow stack Yu-cheng Yu
2021-02-04 20:24 ` Kees Cook
2021-02-03 22:55 ` [PATCH v19 17/25] mm/mmap: Add shadow stack pages to memory accounting Yu-cheng Yu
2021-02-04 20:24 ` Kees Cook
2021-02-03 22:55 ` [PATCH v19 18/25] mm: Update can_follow_write_pte() for shadow stack Yu-cheng Yu
2021-02-04 20:27 ` Kees Cook
2021-02-03 22:55 ` [PATCH v19 19/25] mm: Re-introduce vm_flags to do_mmap() Yu-cheng Yu
2021-02-04 20:28 ` Kees Cook
2021-02-03 22:55 ` [PATCH v19 20/25] x86/cet/shstk: User-mode shadow stack support Yu-cheng Yu
2021-02-04 20:29 ` Kees Cook
2021-02-03 22:55 ` [PATCH v19 21/25] x86/cet/shstk: Handle signals for shadow stack Yu-cheng Yu
2021-02-03 22:55 ` [PATCH v19 22/25] ELF: Introduce arch_setup_elf_property() Yu-cheng Yu
2021-02-04 20:33 ` Kees Cook
2021-02-03 22:55 ` Yu-cheng Yu [this message]
2021-02-03 22:55 ` [PATCH v19 24/25] x86/cet/shstk: Add arch_prctl functions for shadow stack Yu-cheng Yu
2021-02-04 20:35 ` Kees Cook
2021-02-04 23:41 ` Yu, Yu-cheng
2021-02-05 18:26 ` Kees Cook
2021-02-03 22:55 ` [PATCH v19 25/25] mm: Introduce PROT_SHSTK " Yu-cheng Yu
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