[OPTIONAL/RFC v2 38/39] x86/cet/shstk: Add ARCH_CET_UNLOCK
From: Rick Edgecombe <rick.p.edgecombe@intel.com>
Date: 2022-09-29 22:37:56
Also in:
linux-arch, linux-doc, linux-mm, lkml
Subsystem:
documentation, the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Jonathan Corbet, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
From: Mike Rapoport <redacted> Userspace loaders may lock features before a CRIU restore operation has the chance to set them to whatever state is required by the process being restored. Allow a way for CRIU to unlock features. Add it as an arch_prctl() like the other CET operations, but restrict it being called by the ptrace arch_pctl() interface. Signed-off-by: Mike Rapoport <redacted> [Merged into recent API changes, added commit log and docs] Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com> --- v2: - New patch Documentation/x86/cet.rst | 3 +++ arch/x86/include/uapi/asm/prctl.h | 1 + arch/x86/kernel/process_64.c | 1 + arch/x86/kernel/shstk.c | 9 +++++++-- 4 files changed, 12 insertions(+), 2 deletions(-)
diff --git a/Documentation/x86/cet.rst b/Documentation/x86/cet.rst
index 4a0dfb6830f9..6b270a24ebc3 100644
--- a/Documentation/x86/cet.rst
+++ b/Documentation/x86/cet.rst@@ -81,6 +81,9 @@ arch_prctl(ARCH_CET_DISABLE, unsigned int feature) arch_prctl(ARCH_CET_LOCK, unsigned int features) Lock in features at their current enabled or disabled status. +arch_prctl(ARCH_CET_UNLOCK, unsigned int features) + Unlock features. + The return values are as following: On success, return 0. On error, errno can be::
diff --git a/arch/x86/include/uapi/asm/prctl.h b/arch/x86/include/uapi/asm/prctl.h
index d811f0c5fc4f..2f4d81ab4849 100644
--- a/arch/x86/include/uapi/asm/prctl.h
+++ b/arch/x86/include/uapi/asm/prctl.h@@ -25,6 +25,7 @@ #define ARCH_CET_ENABLE 0x4001 #define ARCH_CET_DISABLE 0x4002 #define ARCH_CET_LOCK 0x4003 +#define ARCH_CET_UNLOCK 0x4004 #define CET_SHSTK 0x1 #define CET_WRSS 0x2
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index be544b4b4c8b..fbb2062dd0d2 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c@@ -834,6 +834,7 @@ long do_arch_prctl_64(struct task_struct *task, int option, unsigned long arg2) case ARCH_CET_ENABLE: case ARCH_CET_DISABLE: case ARCH_CET_LOCK: + case ARCH_CET_UNLOCK: return cet_prctl(task, option, arg2); default: ret = -EINVAL;
diff --git a/arch/x86/kernel/shstk.c b/arch/x86/kernel/shstk.c
index 0efec02dbe6b..af1255164f0c 100644
--- a/arch/x86/kernel/shstk.c
+++ b/arch/x86/kernel/shstk.c@@ -464,9 +464,14 @@ long cet_prctl(struct task_struct *task, int option, unsigned long features) return 0; } - /* Don't allow via ptrace */ - if (task != current) + /* Only allow via ptrace */ + if (task != current) { + if (option == ARCH_CET_UNLOCK) { + task->thread.features_locked &= ~features; + return 0; + } return -EINVAL; + } /* Do not allow to change locked features */ if (features & task->thread.features_locked)
--
2.17.1