From 223293205a7265c8b02882461ba8996650048ade Mon Sep 17 00:00:00 2001
From: hc <hc@nodka.com>
Date: Mon, 11 Dec 2023 06:33:33 +0000
Subject: [PATCH] audio ok

---
 kernel/arch/x86/entry/vsyscall/vsyscall_64.c |   58 ++++++++++++++++++++++++++++++++++++++++------------------
 1 files changed, 40 insertions(+), 18 deletions(-)

diff --git a/kernel/arch/x86/entry/vsyscall/vsyscall_64.c b/kernel/arch/x86/entry/vsyscall/vsyscall_64.c
index 82ed001..44c3310 100644
--- a/kernel/arch/x86/entry/vsyscall/vsyscall_64.c
+++ b/kernel/arch/x86/entry/vsyscall/vsyscall_64.c
@@ -42,9 +42,11 @@
 #define CREATE_TRACE_POINTS
 #include "vsyscall_trace.h"
 
-static enum { EMULATE, NONE } vsyscall_mode =
+static enum { EMULATE, XONLY, NONE } vsyscall_mode __ro_after_init =
 #ifdef CONFIG_LEGACY_VSYSCALL_NONE
 	NONE;
+#elif defined(CONFIG_LEGACY_VSYSCALL_XONLY)
+	XONLY;
 #else
 	EMULATE;
 #endif
@@ -54,6 +56,8 @@
 	if (str) {
 		if (!strcmp("emulate", str))
 			vsyscall_mode = EMULATE;
+		else if (!strcmp("xonly", str))
+			vsyscall_mode = XONLY;
 		else if (!strcmp("none", str))
 			vsyscall_mode = NONE;
 		else
@@ -99,28 +103,22 @@
 	 * sig_on_uaccess_err, this could go away.
 	 */
 
-	if (!access_ok(VERIFY_WRITE, (void __user *)ptr, size)) {
-		siginfo_t info;
+	if (!access_ok((void __user *)ptr, size)) {
 		struct thread_struct *thread = &current->thread;
 
-		thread->error_code	= 6;  /* user fault, no page, write */
+		thread->error_code	= X86_PF_USER | X86_PF_WRITE;
 		thread->cr2		= ptr;
 		thread->trap_nr		= X86_TRAP_PF;
 
-		clear_siginfo(&info);
-		info.si_signo		= SIGSEGV;
-		info.si_errno		= 0;
-		info.si_code		= SEGV_MAPERR;
-		info.si_addr		= (void __user *)ptr;
-
-		force_sig_info(SIGSEGV, &info, current);
+		force_sig_fault(SIGSEGV, SEGV_MAPERR, (void __user *)ptr);
 		return false;
 	} else {
 		return true;
 	}
 }
 
-bool emulate_vsyscall(struct pt_regs *regs, unsigned long address)
+bool emulate_vsyscall(unsigned long error_code,
+		      struct pt_regs *regs, unsigned long address)
 {
 	struct task_struct *tsk;
 	unsigned long caller;
@@ -128,6 +126,22 @@
 	int prev_sig_on_uaccess_err;
 	long ret;
 	unsigned long orig_dx;
+
+	/* Write faults or kernel-privilege faults never get fixed up. */
+	if ((error_code & (X86_PF_WRITE | X86_PF_USER)) != X86_PF_USER)
+		return false;
+
+	if (!(error_code & X86_PF_INSTR)) {
+		/* Failed vsyscall read */
+		if (vsyscall_mode == EMULATE)
+			return false;
+
+		/*
+		 * User code tried and failed to read the vsyscall page.
+		 */
+		warn_bad_vsyscall(KERN_INFO, regs, "vsyscall read attempt denied -- look up the vsyscall kernel parameter if you need a workaround");
+		return false;
+	}
 
 	/*
 	 * No point in checking CS -- the only way to get here is a user mode
@@ -170,7 +184,7 @@
 	 */
 	switch (vsyscall_nr) {
 	case 0:
-		if (!write_ok_or_segv(regs->di, sizeof(struct timeval)) ||
+		if (!write_ok_or_segv(regs->di, sizeof(struct __kernel_old_timeval)) ||
 		    !write_ok_or_segv(regs->si, sizeof(struct timezone))) {
 			ret = -EFAULT;
 			goto check_fault;
@@ -180,7 +194,7 @@
 		break;
 
 	case 1:
-		if (!write_ok_or_segv(regs->di, sizeof(time_t))) {
+		if (!write_ok_or_segv(regs->di, sizeof(__kernel_old_time_t))) {
 			ret = -EFAULT;
 			goto check_fault;
 		}
@@ -208,7 +222,7 @@
 	 */
 	regs->orig_ax = syscall_nr;
 	regs->ax = -ENOSYS;
-	tmp = secure_computing(NULL);
+	tmp = secure_computing();
 	if ((!tmp && regs->orig_ax != syscall_nr) || regs->ip != address) {
 		warn_bad_vsyscall(KERN_DEBUG, regs,
 				  "seccomp tried to change syscall nr or ip");
@@ -275,7 +289,7 @@
 	return true;
 
 sigsegv:
-	force_sig(SIGSEGV, current);
+	force_sig(SIGSEGV);
 	return true;
 }
 
@@ -291,7 +305,7 @@
 static const struct vm_operations_struct gate_vma_ops = {
 	.name = gate_vma_name,
 };
-static struct vm_area_struct gate_vma = {
+static struct vm_area_struct gate_vma __ro_after_init = {
 	.vm_start	= VSYSCALL_ADDR,
 	.vm_end		= VSYSCALL_ADDR + PAGE_SIZE,
 	.vm_page_prot	= PAGE_READONLY_EXEC,
@@ -364,12 +378,20 @@
 	extern char __vsyscall_page;
 	unsigned long physaddr_vsyscall = __pa_symbol(&__vsyscall_page);
 
-	if (vsyscall_mode != NONE) {
+	/*
+	 * For full emulation, the page needs to exist for real.  In
+	 * execute-only mode, there is no PTE at all backing the vsyscall
+	 * page.
+	 */
+	if (vsyscall_mode == EMULATE) {
 		__set_fixmap(VSYSCALL_PAGE, physaddr_vsyscall,
 			     PAGE_KERNEL_VVAR);
 		set_vsyscall_pgtable_user_bits(swapper_pg_dir);
 	}
 
+	if (vsyscall_mode == XONLY)
+		gate_vma.vm_flags = VM_EXEC;
+
 	BUILD_BUG_ON((unsigned long)__fix_to_virt(VSYSCALL_PAGE) !=
 		     (unsigned long)VSYSCALL_ADDR);
 }

--
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