linux-kernel - [GIT pull V2] x86/core for v6.6-rc1

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Date:   Wed, 30 Aug 2023 15:27:05 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org
Subject: [GIT pull V2] x86/core for v6.6-rc1

Linus,

please pull the latest x86/core branch from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86-core-2023-08-30-v2

up to:  b65413768abd: x86/kprobes: Prohibit probing on compiler generated CFI checking code


X86 core updates:

  - Prevent kprobes on compiler generated CFI checking code.

    The compiler generates a instruction sequence for indirect call
    checks. If this sequence is modified with a kprobe, then the check
    fails. So the instructions must be protected against probing.

  - A few minor cleanups for the SMP code

Thanks,

	tglx

Thanks,

	tglx

------------------>
Masami Hiramatsu (1):
      x86/kprobes: Prohibit probing on compiler generated CFI checking code

Sohil Mehta (3):
      x86/smpboot: Remove a stray comment about CPU hotplug
      x86/smp: Remove a non-existent function declaration
      x86/smpboot: Change smp_store_boot_cpu_info() to static


 arch/x86/include/asm/smp.h     |  3 ---
 arch/x86/kernel/kprobes/core.c | 34 ++++++++++++++++++++++++++++++++++
 arch/x86/kernel/smpboot.c      |  6 ++----
 include/linux/cfi.h            |  4 +++-
 4 files changed, 39 insertions(+), 8 deletions(-)

diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
index 600cf25dbfc6..cf7217ad5701 100644
--- a/arch/x86/include/asm/smp.h
+++ b/arch/x86/include/asm/smp.h
@@ -132,11 +132,8 @@ void smp_kick_mwait_play_dead(void);
 void native_smp_send_reschedule(int cpu);
 void native_send_call_func_ipi(const struct cpumask *mask);
 void native_send_call_func_single_ipi(int cpu);
-void x86_idle_thread_init(unsigned int cpu, struct task_struct *idle);
 
 bool smp_park_other_cpus_in_init(void);
-
-void smp_store_boot_cpu_info(void);
 void smp_store_cpu_info(int id);
 
 asmlinkage __visible void smp_reboot_interrupt(void);
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index f7f6042eb7e6..e8babebad7b8 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -45,6 +45,7 @@
 #include <linux/vmalloc.h>
 #include <linux/pgtable.h>
 #include <linux/set_memory.h>
+#include <linux/cfi.h>
 
 #include <asm/text-patching.h>
 #include <asm/cacheflush.h>
@@ -293,7 +294,40 @@ static int can_probe(unsigned long paddr)
 #endif
 		addr += insn.length;
 	}
+	if (IS_ENABLED(CONFIG_CFI_CLANG)) {
+		/*
+		 * The compiler generates the following instruction sequence
+		 * for indirect call checks and cfi.c decodes this;
+		 *
+		 *   movl    -<id>, %r10d       ; 6 bytes
+		 *   addl    -4(%reg), %r10d    ; 4 bytes
+		 *   je      .Ltmp1             ; 2 bytes
+		 *   ud2                        ; <- regs->ip
+		 *   .Ltmp1:
+		 *
+		 * Also, these movl and addl are used for showing expected
+		 * type. So those must not be touched.
+		 */
+		__addr = recover_probed_instruction(buf, addr);
+		if (!__addr)
+			return 0;
+
+		if (insn_decode_kernel(&insn, (void *)__addr) < 0)
+			return 0;
+
+		if (insn.opcode.value == 0xBA)
+			offset = 12;
+		else if (insn.opcode.value == 0x3)
+			offset = 6;
+		else
+			goto out;
+
+		/* This movl/addl is used for decoding CFI. */
+		if (is_cfi_trap(addr + offset))
+			return 0;
+	}
 
+out:
 	return (addr == paddr);
 }
 
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index e1aa2cd7734b..28c590b4b1b1 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -422,7 +422,7 @@ int topology_update_die_map(unsigned int die, unsigned int cpu)
 	return 0;
 }
 
-void __init smp_store_boot_cpu_info(void)
+static void __init smp_store_boot_cpu_info(void)
 {
 	int id = 0; /* CPU 0 */
 	struct cpuinfo_x86 *c = &cpu_data(id);
@@ -1614,9 +1614,7 @@ void play_dead_common(void)
 	idle_task_exit();
 
 	cpuhp_ap_report_dead();
-	/*
-	 * With physical CPU hotplug, we should halt the cpu
-	 */
+
 	local_irq_disable();
 }
 
diff --git a/include/linux/cfi.h b/include/linux/cfi.h
index 5e134f4ce8b7..3552ec82b725 100644
--- a/include/linux/cfi.h
+++ b/include/linux/cfi.h
@@ -19,11 +19,13 @@ static inline enum bug_trap_type report_cfi_failure_noaddr(struct pt_regs *regs,
 {
 	return report_cfi_failure(regs, addr, NULL, 0);
 }
+#endif /* CONFIG_CFI_CLANG */
 
 #ifdef CONFIG_ARCH_USES_CFI_TRAPS
 bool is_cfi_trap(unsigned long addr);
+#else
+static inline bool is_cfi_trap(unsigned long addr) { return false; }
 #endif
-#endif /* CONFIG_CFI_CLANG */
 
 #ifdef CONFIG_MODULES
 #ifdef CONFIG_ARCH_USES_CFI_TRAPS