linux-kernel - [PATCH v9 36/42] x86: Expose thread features in /proc/$PID/status

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <20230613001108.3040476-37-rick.p.edgecombe@intel.com>
Date:   Mon, 12 Jun 2023 17:11:02 -0700
From:   Rick Edgecombe <rick.p.edgecombe@...el.com>
To:     x86@...nel.org, "H . Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-mm@...ck.org,
        linux-arch@...r.kernel.org, linux-api@...r.kernel.org,
        Arnd Bergmann <arnd@...db.de>,
        Andy Lutomirski <luto@...nel.org>,
        Balbir Singh <bsingharora@...il.com>,
        Borislav Petkov <bp@...en8.de>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Eugene Syromiatnikov <esyr@...hat.com>,
        Florian Weimer <fweimer@...hat.com>,
        "H . J . Lu" <hjl.tools@...il.com>, Jann Horn <jannh@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Kees Cook <keescook@...omium.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Oleg Nesterov <oleg@...hat.com>, Pavel Machek <pavel@....cz>,
        Peter Zijlstra <peterz@...radead.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        Weijiang Yang <weijiang.yang@...el.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        John Allen <john.allen@....com>, kcc@...gle.com,
        eranian@...gle.com, rppt@...nel.org, jamorris@...ux.microsoft.com,
        dethoma@...rosoft.com, akpm@...ux-foundation.org,
        Andrew.Cooper3@...rix.com, christina.schimpe@...el.com,
        david@...hat.com, debug@...osinc.com, szabolcs.nagy@....com,
        torvalds@...ux-foundation.org, broonie@...nel.org
Cc:     rick.p.edgecombe@...el.com, Pengfei Xu <pengfei.xu@...el.com>
Subject: [PATCH v9 36/42] x86: Expose thread features in /proc/$PID/status

Applications and loaders can have logic to decide whether to enable
shadow stack. They usually don't report whether shadow stack has been
enabled or not, so there is no way to verify whether an application
actually is protected by shadow stack.

Add two lines in /proc/$PID/status to report enabled and locked features.

Since, this involves referring to arch specific defines in asm/prctl.h,
implement an arch breakout to emit the feature lines.

[Switched to CET, added to commit log]

Co-developed-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
Reviewed-by: Borislav Petkov (AMD) <bp@...en8.de>
Reviewed-by: Kees Cook <keescook@...omium.org>
Acked-by: Mike Rapoport (IBM) <rppt@...nel.org>
Tested-by: Pengfei Xu <pengfei.xu@...el.com>
Tested-by: John Allen <john.allen@....com>
Tested-by: Kees Cook <keescook@...omium.org>
---
 arch/x86/kernel/cpu/proc.c | 23 +++++++++++++++++++++++
 fs/proc/array.c            |  6 ++++++
 include/linux/proc_fs.h    |  2 ++
 3 files changed, 31 insertions(+)

diff --git a/arch/x86/kernel/cpu/proc.c b/arch/x86/kernel/cpu/proc.c
index 099b6f0d96bd..31c0e68f6227 100644
--- a/arch/x86/kernel/cpu/proc.c
+++ b/arch/x86/kernel/cpu/proc.c
@@ -4,6 +4,8 @@
 #include <linux/string.h>
 #include <linux/seq_file.h>
 #include <linux/cpufreq.h>
+#include <asm/prctl.h>
+#include <linux/proc_fs.h>
 
 #include "cpu.h"
 
@@ -175,3 +177,24 @@ const struct seq_operations cpuinfo_op = {
 	.stop	= c_stop,
 	.show	= show_cpuinfo,
 };
+
+#ifdef CONFIG_X86_USER_SHADOW_STACK
+static void dump_x86_features(struct seq_file *m, unsigned long features)
+{
+	if (features & ARCH_SHSTK_SHSTK)
+		seq_puts(m, "shstk ");
+	if (features & ARCH_SHSTK_WRSS)
+		seq_puts(m, "wrss ");
+}
+
+void arch_proc_pid_thread_features(struct seq_file *m, struct task_struct *task)
+{
+	seq_puts(m, "x86_Thread_features:\t");
+	dump_x86_features(m, task->thread.features);
+	seq_putc(m, '\n');
+
+	seq_puts(m, "x86_Thread_features_locked:\t");
+	dump_x86_features(m, task->thread.features_locked);
+	seq_putc(m, '\n');
+}
+#endif /* CONFIG_X86_USER_SHADOW_STACK */
diff --git a/fs/proc/array.c b/fs/proc/array.c
index d35bbf35a874..2c2efbe685d8 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -431,6 +431,11 @@ static inline void task_untag_mask(struct seq_file *m, struct mm_struct *mm)
 	seq_printf(m, "untag_mask:\t%#lx\n", mm_untag_mask(mm));
 }
 
+__weak void arch_proc_pid_thread_features(struct seq_file *m,
+					  struct task_struct *task)
+{
+}
+
 int proc_pid_status(struct seq_file *m, struct pid_namespace *ns,
 			struct pid *pid, struct task_struct *task)
 {
@@ -455,6 +460,7 @@ int proc_pid_status(struct seq_file *m, struct pid_namespace *ns,
 	task_cpus_allowed(m, task);
 	cpuset_task_status_allowed(m, task);
 	task_context_switch_counts(m, task);
+	arch_proc_pid_thread_features(m, task);
 	return 0;
 }
 
diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index 0260f5ea98fe..80ff8e533cbd 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -158,6 +158,8 @@ int proc_pid_arch_status(struct seq_file *m, struct pid_namespace *ns,
 			struct pid *pid, struct task_struct *task);
 #endif /* CONFIG_PROC_PID_ARCH_STATUS */
 
+void arch_proc_pid_thread_features(struct seq_file *m, struct task_struct *task);
+
 #else /* CONFIG_PROC_FS */
 
 static inline void proc_root_init(void)
-- 
2.34.1