Merge tag 'x86-urgent-2026-04-24' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 fixes from Ingo Molnar:

 - Prevent deadlock during shstk sigreturn (Rick Edgecombe)

 - Disable FRED when PTI is forced on (Dave Hansen)

 - Revert a CPA INVLPGB optimization that did not properly handle
   discontiguous virtual addresses (Dave Hansen)

* tag 'x86-urgent-2026-04-24' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/mm: Revert INVLPGB optimization for set_memory code
  x86/cpu: Disable FRED when PTI is forced on
  x86/shstk: Prevent deadlock during shstk sigreturn

arch/x86/Kconfig

@@ -1885,6 +1885,7 @@ config X86_USER_SHADOW_STACK
 	bool "X86 userspace shadow stack"
 	depends on AS_WRUSS
 	depends on X86_64
+	depends on PER_VMA_LOCK
 	select ARCH_USES_HIGH_VMA_FLAGS
 	select ARCH_HAS_USER_SHADOW_STACK
 	select X86_CET

arch/x86/kernel/shstk.c

@@ -326,10 +326,8 @@ static int shstk_push_sigframe(unsigned long *ssp)
 
 static int shstk_pop_sigframe(unsigned long *ssp)
 {
-	struct vm_area_struct *vma;
 	unsigned long token_addr;
-	bool need_to_check_vma;
-	int err = 1;
+	unsigned int seq;
 
 	/*
 	 * It is possible for the SSP to be off the end of a shadow stack by 4
@@ -340,25 +338,35 @@ static int shstk_pop_sigframe(unsigned long *ssp)
 	if (!IS_ALIGNED(*ssp, 8))
 		return -EINVAL;
 
-	need_to_check_vma = PAGE_ALIGN(*ssp) == *ssp;
+	do {
+		struct vm_area_struct *vma;
+		bool valid_vma;
+		int err;
 
-	if (need_to_check_vma)
 		if (mmap_read_lock_killable(current->mm))
 			return -EINTR;
 
-	err = get_shstk_data(&token_addr, (unsigned long __user *)*ssp);
-	if (unlikely(err))
-		goto out_err;
-
-	if (need_to_check_vma) {
 		vma = find_vma(current->mm, *ssp);
-		if (!vma || !(vma->vm_flags & VM_SHADOW_STACK)) {
-			err = -EFAULT;
-			goto out_err;
-		}
+		valid_vma = vma && (vma->vm_flags & VM_SHADOW_STACK);
 
+		/*
+		 * VMAs can change between get_shstk_data() and find_vma().
+		 * Watch for changes and ensure that 'token_addr' comes from
+		 * 'vma' by recording a seqcount.
+		 *
+		 * Ignore the return value of mmap_lock_speculate_try_begin()
+		 * because the mmap lock excludes the possibility of writers.
+		 */
+		mmap_lock_speculate_try_begin(current->mm, &seq);
 		mmap_read_unlock(current->mm);
-	}
+
+		if (!valid_vma)
+			return -EINVAL;
+
+		err = get_shstk_data(&token_addr, (unsigned long __user *)*ssp);
+		if (err)
+			return err;
+	} while (mmap_lock_speculate_retry(current->mm, seq));
 
 	/* Restore SSP aligned? */
 	if (unlikely(!IS_ALIGNED(token_addr, 8)))
@@ -371,10 +379,6 @@ static int shstk_pop_sigframe(unsigned long *ssp)
 	*ssp = token_addr;
 
 	return 0;
-out_err:
-	if (need_to_check_vma)
-		mmap_read_unlock(current->mm);
-	return err;
 }
 
 int setup_signal_shadow_stack(struct ksignal *ksig)

arch/x86/mm/pat/set_memory.c

@@ -399,6 +399,15 @@ static void cpa_flush_all(unsigned long cache)
 	on_each_cpu(__cpa_flush_all, (void *) cache, 1);
 }
 
+static void __cpa_flush_tlb(void *data)
+{
+	struct cpa_data *cpa = data;
+	unsigned int i;
+
+	for (i = 0; i < cpa->numpages; i++)
+		flush_tlb_one_kernel(fix_addr(__cpa_addr(cpa, i)));
+}
+
 static int collapse_large_pages(unsigned long addr, struct list_head *pgtables);
 
 static void cpa_collapse_large_pages(struct cpa_data *cpa)
@@ -435,7 +444,6 @@ static void cpa_collapse_large_pages(struct cpa_data *cpa)
 
 static void cpa_flush(struct cpa_data *cpa, int cache)
 {
-	unsigned long start, end;
 	unsigned int i;
 
 	BUG_ON(irqs_disabled() && !early_boot_irqs_disabled);
@@ -445,12 +453,10 @@ static void cpa_flush(struct cpa_data *cpa, int cache)
 		goto collapse_large_pages;
 	}
 
-	start = fix_addr(__cpa_addr(cpa, 0));
-	end =   start + cpa->numpages * PAGE_SIZE;
-	if (cpa->force_flush_all)
-		end = TLB_FLUSH_ALL;
-
-	flush_tlb_kernel_range(start, end);
+	if (cpa->force_flush_all || cpa->numpages > tlb_single_page_flush_ceiling)
+		flush_tlb_all();
+	else
+		on_each_cpu(__cpa_flush_tlb, cpa, 1);
 
 	if (!cache)
 		goto collapse_large_pages;

arch/x86/mm/pti.c

@@ -105,6 +105,11 @@ void __init pti_check_boottime_disable(void)
 		pr_debug("PTI enabled, disabling INVLPGB\n");
 		setup_clear_cpu_cap(X86_FEATURE_INVLPGB);
 	}
+
+	if (cpu_feature_enabled(X86_FEATURE_FRED)) {
+		pr_debug("PTI enabled, disabling FRED\n");
+		setup_clear_cpu_cap(X86_FEATURE_FRED);
+	}
 }
 
 static int __init pti_parse_cmdline(char *arg)