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

1 files changed, 24 insertions, 20 deletions

diff --git a/arch/x86/kernel/shstk.c b/arch/x86/kernel/shstk.c
index 0962ae4c3017..0ca64900192f 100644
--- a/arch/x86/kernel/shstk.c
+++ b/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)