From: Deepak Gupta <debug@rivosinc.com>
To: paul.walmsley@sifive.com, rick.p.edgecombe@intel.com,
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jhubbard@nvidia.com
Subject: [PATCH v3 18/29] riscv: Implements arch agnostic shadow stack prctls
Date: Wed, 3 Apr 2024 16:35:06 -0700 [thread overview]
Message-ID: <20240403234054.2020347-19-debug@rivosinc.com> (raw)
In-Reply-To: <20240403234054.2020347-1-debug@rivosinc.com>
Implement architecture agnostic prctls() interface for setting and getting
shadow stack status.
prctls implemented are PR_GET_SHADOW_STACK_STATUS,
PR_SET_SHADOW_STACK_STATUS and PR_LOCK_SHADOW_STACK_STATUS.
As part of PR_SET_SHADOW_STACK_STATUS/PR_GET_SHADOW_STACK_STATUS, only
PR_SHADOW_STACK_ENABLE is implemented because RISCV allows each mode to
write to their own shadow stack using `sspush` or `ssamoswap`.
PR_LOCK_SHADOW_STACK_STATUS locks current configuration of shadow stack
enabling.
Signed-off-by: Deepak Gupta <debug@rivosinc.com>
---
arch/riscv/include/asm/usercfi.h | 18 +++++-
arch/riscv/kernel/process.c | 8 +++
arch/riscv/kernel/usercfi.c | 107 +++++++++++++++++++++++++++++++
3 files changed, 132 insertions(+), 1 deletion(-)
diff --git a/arch/riscv/include/asm/usercfi.h b/arch/riscv/include/asm/usercfi.h
index b47574a7a8c9..a168ae0fa5d8 100644
--- a/arch/riscv/include/asm/usercfi.h
+++ b/arch/riscv/include/asm/usercfi.h
@@ -7,6 +7,7 @@
#ifndef __ASSEMBLY__
#include <linux/types.h>
+#include <linux/prctl.h>
struct task_struct;
struct kernel_clone_args;
@@ -14,7 +15,8 @@ struct kernel_clone_args;
#ifdef CONFIG_RISCV_USER_CFI
struct cfi_status {
unsigned long ubcfi_en : 1; /* Enable for backward cfi. */
- unsigned long rsvd : ((sizeof(unsigned long)*8) - 1);
+ unsigned long ubcfi_locked : 1;
+ unsigned long rsvd : ((sizeof(unsigned long)*8) - 2);
unsigned long user_shdw_stk; /* Current user shadow stack pointer */
unsigned long shdw_stk_base; /* Base address of shadow stack */
unsigned long shdw_stk_size; /* size of shadow stack */
@@ -26,6 +28,10 @@ void shstk_release(struct task_struct *tsk);
void set_shstk_base(struct task_struct *task, unsigned long shstk_addr, unsigned long size);
void set_active_shstk(struct task_struct *task, unsigned long shstk_addr);
bool is_shstk_enabled(struct task_struct *task);
+bool is_shstk_locked(struct task_struct *task);
+void set_shstk_status(struct task_struct *task, bool enable);
+
+#define PR_SHADOW_STACK_SUPPORTED_STATUS_MASK (PR_SHADOW_STACK_ENABLE)
#else
@@ -56,6 +62,16 @@ static inline bool is_shstk_enabled(struct task_struct *task)
return false;
}
+static inline bool is_shstk_locked(struct task_struct *task)
+{
+ return false;
+}
+
+static inline void set_shstk_status(struct task_struct *task, bool enable)
+{
+
+}
+
#endif /* CONFIG_RISCV_USER_CFI */
#endif /* __ASSEMBLY__ */
diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
index ef48a25b0eff..3fb8b23f629b 100644
--- a/arch/riscv/kernel/process.c
+++ b/arch/riscv/kernel/process.c
@@ -145,6 +145,14 @@ void start_thread(struct pt_regs *regs, unsigned long pc,
regs->epc = pc;
regs->sp = sp;
+ /*
+ * clear shadow stack state on exec.
+ * libc will set it later via prctl.
+ */
+ set_shstk_status(current, false);
+ set_shstk_base(current, 0, 0);
+ set_active_shstk(current, 0);
+
#ifdef CONFIG_64BIT
regs->status &= ~SR_UXL;
diff --git a/arch/riscv/kernel/usercfi.c b/arch/riscv/kernel/usercfi.c
index 11ef7ab925c9..cdedf1f78b3e 100644
--- a/arch/riscv/kernel/usercfi.c
+++ b/arch/riscv/kernel/usercfi.c
@@ -24,6 +24,16 @@ bool is_shstk_enabled(struct task_struct *task)
return task->thread_info.user_cfi_state.ubcfi_en ? true : false;
}
+bool is_shstk_allocated(struct task_struct *task)
+{
+ return task->thread_info.user_cfi_state.shdw_stk_base ? true : false;
+}
+
+bool is_shstk_locked(struct task_struct *task)
+{
+ return task->thread_info.user_cfi_state.ubcfi_locked ? true : false;
+}
+
void set_shstk_base(struct task_struct *task, unsigned long shstk_addr, unsigned long size)
{
task->thread_info.user_cfi_state.shdw_stk_base = shstk_addr;
@@ -42,6 +52,23 @@ void set_active_shstk(struct task_struct *task, unsigned long shstk_addr)
task->thread_info.user_cfi_state.user_shdw_stk = shstk_addr;
}
+void set_shstk_status(struct task_struct *task, bool enable)
+{
+ task->thread_info.user_cfi_state.ubcfi_en = enable ? 1 : 0;
+
+ if (enable)
+ task->thread_info.envcfg |= ENVCFG_SSE;
+ else
+ task->thread_info.envcfg &= ~ENVCFG_SSE;
+
+ csr_write(CSR_ENVCFG, task->thread_info.envcfg);
+}
+
+void set_shstk_lock(struct task_struct *task)
+{
+ task->thread_info.user_cfi_state.ubcfi_locked = 1;
+}
+
/*
* If size is 0, then to be compatible with regular stack we want it to be as big as
* regular stack. Else PAGE_ALIGN it and return back
@@ -268,3 +295,83 @@ void shstk_release(struct task_struct *tsk)
vm_munmap(base, size);
set_shstk_base(tsk, 0, 0);
}
+
+int arch_get_shadow_stack_status(struct task_struct *t, unsigned long __user *status)
+{
+ unsigned long bcfi_status = 0;
+
+ if (!cpu_supports_shadow_stack())
+ return -EINVAL;
+
+ /* this means shadow stack is enabled on the task */
+ bcfi_status |= (is_shstk_enabled(t) ? PR_SHADOW_STACK_ENABLE : 0);
+
+ return copy_to_user(status, &bcfi_status, sizeof(bcfi_status)) ? -EFAULT : 0;
+}
+
+int arch_set_shadow_stack_status(struct task_struct *t, unsigned long status)
+{
+ unsigned long size = 0, addr = 0;
+ bool enable_shstk = false;
+
+ if (!cpu_supports_shadow_stack())
+ return -EINVAL;
+
+ /* Reject unknown flags */
+ if (status & ~PR_SHADOW_STACK_SUPPORTED_STATUS_MASK)
+ return -EINVAL;
+
+ /* bcfi status is locked and further can't be modified by user */
+ if (is_shstk_locked(t))
+ return -EINVAL;
+
+ enable_shstk = status & PR_SHADOW_STACK_ENABLE;
+ /* Request is to enable shadow stack and shadow stack is not enabled already */
+ if (enable_shstk && !is_shstk_enabled(t)) {
+ /* shadow stack was allocated and enable request again
+ * no need to support such usecase and return EINVAL.
+ */
+ if (is_shstk_allocated(t))
+ return -EINVAL;
+
+ size = calc_shstk_size(0);
+ addr = allocate_shadow_stack(0, size, 0, false);
+ if (IS_ERR_VALUE(addr))
+ return -ENOMEM;
+ set_shstk_base(t, addr, size);
+ set_active_shstk(t, addr + size);
+ }
+
+ /*
+ * If a request to disable shadow stack happens, let's go ahead and release it
+ * Although, if CLONE_VFORKed child did this, then in that case we will end up
+ * not releasing the shadow stack (because it might be needed in parent). Although
+ * we will disable it for VFORKed child. And if VFORKed child tries to enable again
+ * then in that case, it'll get entirely new shadow stack because following condition
+ * are true
+ * - shadow stack was not enabled for vforked child
+ * - shadow stack base was anyways pointing to 0
+ * This shouldn't be a big issue because we want parent to have availability of shadow
+ * stack whenever VFORKed child releases resources via exit or exec but at the same
+ * time we want VFORKed child to break away and establish new shadow stack if it desires
+ *
+ */
+ if (!enable_shstk)
+ shstk_release(t);
+
+ set_shstk_status(t, enable_shstk);
+ return 0;
+}
+
+int arch_lock_shadow_stack_status(struct task_struct *task,
+ unsigned long arg)
+{
+ /* If shtstk not supported or not enabled on task, nothing to lock here */
+ if (!cpu_supports_shadow_stack() ||
+ !is_shstk_enabled(task))
+ return -EINVAL;
+
+ set_shstk_lock(task);
+
+ return 0;
+}
--
2.43.2
next prev parent reply other threads:[~2024-04-03 23:42 UTC|newest]
Thread overview: 82+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-03 23:34 [PATCH v3 00/29] riscv control-flow integrity for usermode Deepak Gupta
2024-04-03 23:34 ` [PATCH v3 01/29] riscv: envcfg save and restore on task switching Deepak Gupta
2024-05-09 0:10 ` Charlie Jenkins
2024-05-09 19:00 ` Deepak Gupta
2024-04-03 23:34 ` [PATCH v3 02/29] riscv: define default value for envcfg for task Deepak Gupta
2024-05-10 22:33 ` Charlie Jenkins
2024-05-13 18:33 ` Deepak Gupta
2024-04-03 23:34 ` [PATCH v3 03/29] riscv/Kconfig: enable HAVE_EXIT_THREAD for riscv Deepak Gupta
2024-05-10 22:36 ` Charlie Jenkins
2024-04-03 23:34 ` [PATCH v3 04/29] riscv: zicfilp / zicfiss in dt-bindings (extensions.yaml) Deepak Gupta
2024-04-10 11:58 ` Rob Herring
2024-04-10 21:37 ` Deepak Gupta
2024-04-15 19:41 ` Rob Herring
2024-04-16 15:44 ` Deepak Gupta
2024-05-09 18:14 ` Conor Dooley
2024-05-09 18:46 ` Deepak Gupta
2024-05-09 20:32 ` Conor Dooley
2024-05-09 23:26 ` Deepak Gupta
2024-04-03 23:34 ` [PATCH v3 05/29] riscv: zicfiss / zicfilp enumeration Deepak Gupta
2024-05-09 0:00 ` Andy Chiu
2024-05-09 0:07 ` Charlie Jenkins
2024-04-03 23:34 ` [PATCH v3 06/29] riscv: zicfiss / zicfilp extension csr and bit definitions Deepak Gupta
2024-05-10 22:37 ` Charlie Jenkins
2024-04-03 23:34 ` [PATCH v3 07/29] riscv: usercfi state for task and save/restore of CSR_SSP on trap entry/exit Deepak Gupta
2024-05-10 22:51 ` Charlie Jenkins
2024-04-03 23:34 ` [PATCH v3 08/29] mm: Define VM_SHADOW_STACK for RISC-V Deepak Gupta
2024-04-04 18:58 ` David Hildenbrand
2024-04-04 19:04 ` Mark Brown
2024-04-04 19:15 ` David Hildenbrand
2024-04-04 19:21 ` Deepak Gupta
2024-04-03 23:34 ` [PATCH v3 09/29] mm: abstract shadow stack vma behind `vma_is_shadow_stack` Deepak Gupta
2024-04-04 19:02 ` David Hildenbrand
2024-04-04 21:39 ` Deepak Gupta
2024-04-03 23:34 ` [PATCH v3 10/29] riscv/mm : ensure PROT_WRITE leads to VM_READ | VM_WRITE Deepak Gupta
2024-05-10 21:02 ` Charlie Jenkins
2024-05-13 17:47 ` Deepak Gupta
2024-05-13 18:36 ` Charlie Jenkins
2024-05-13 18:41 ` Deepak Gupta
2024-05-13 21:26 ` Charlie Jenkins
2024-05-12 16:24 ` Alexandre Ghiti
2024-05-13 18:29 ` Deepak Gupta
2024-04-03 23:34 ` [PATCH v3 11/29] riscv mm: manufacture shadow stack pte Deepak Gupta
2024-05-12 16:26 ` Alexandre Ghiti
2024-04-03 23:35 ` [PATCH v3 12/29] riscv mmu: teach pte_mkwrite to manufacture shadow stack PTEs Deepak Gupta
2024-05-12 16:28 ` Alexandre Ghiti
2024-05-13 17:33 ` Deepak Gupta
2024-04-03 23:35 ` [PATCH v3 13/29] riscv mmu: write protect and shadow stack Deepak Gupta
2024-05-12 16:31 ` Alexandre Ghiti
2024-05-13 17:32 ` Deepak Gupta
2024-05-23 14:59 ` Alexandre Ghiti
2024-05-24 7:16 ` Deepak Gupta
2024-04-03 23:35 ` [PATCH v3 14/29] riscv/mm: Implement map_shadow_stack() syscall Deepak Gupta
2024-05-12 16:50 ` Alexandre Ghiti
2024-05-13 17:25 ` Deepak Gupta
2024-04-03 23:35 ` [PATCH v3 15/29] riscv/shstk: If needed allocate a new shadow stack on clone Deepak Gupta
2024-05-12 17:05 ` Alexandre Ghiti
2024-05-13 17:10 ` Deepak Gupta
2024-04-03 23:35 ` [PATCH v3 16/29] prctl: arch-agnostic prctl for shadow stack Deepak Gupta
2024-04-03 23:35 ` [PATCH v3 17/29] prctl: arch-agnostic prctl for indirect branch tracking Deepak Gupta
2024-05-10 23:29 ` Charlie Jenkins
2024-05-13 18:31 ` Deepak Gupta
2024-04-03 23:35 ` Deepak Gupta [this message]
2024-04-03 23:35 ` [PATCH v3 19/29] riscv: Implements arch agnostic indirect branch tracking prctls Deepak Gupta
2024-04-03 23:35 ` [PATCH v3 20/29] riscv/kernel: update __show_regs to print shadow stack register Deepak Gupta
2024-05-12 17:10 ` Alexandre Ghiti
2024-04-03 23:35 ` [PATCH v3 21/29] riscv/traps: Introduce software check exception Deepak Gupta
2024-04-03 23:35 ` [PATCH v3 22/29] riscv sigcontext: adding cfi state field in sigcontext Deepak Gupta
2024-05-24 9:46 ` Andy Chiu
2024-05-24 19:11 ` Deepak Gupta
2024-04-03 23:35 ` [PATCH v3 23/29] riscv signal: Save and restore of shadow stack for signal Deepak Gupta
2024-04-03 23:35 ` [PATCH v3 24/29] riscv/ptrace: riscv cfi status and state via ptrace and in core files Deepak Gupta
2024-04-03 23:35 ` [PATCH v3 25/29] riscv/hwprobe: zicfilp / zicfiss enumeration in hwprobe Deepak Gupta
2024-04-03 23:35 ` [PATCH v3 26/29] riscv: create a config for shadow stack and landing pad instr support Deepak Gupta
2024-04-03 23:35 ` [PATCH v3 27/29] riscv: Documentation for landing pad / indirect branch tracking Deepak Gupta
2024-05-10 20:30 ` Charlie Jenkins
2024-05-13 17:07 ` Deepak Gupta
2024-04-03 23:35 ` [PATCH v3 28/29] riscv: Documentation for shadow stack on riscv Deepak Gupta
2024-04-03 23:35 ` [PATCH v3 29/29] kselftest/riscv: kselftest for user mode cfi Deepak Gupta
2024-05-09 18:21 ` Charlie Jenkins
2024-05-09 19:16 ` Deepak Gupta
2024-05-10 1:20 ` Charlie Jenkins
2024-05-09 0:33 ` [PATCH v3 00/29] riscv control-flow integrity for usermode Charlie Jenkins
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