1 files changed, 7 insertions, 2 deletions

diff --git a/arch/x86/mm/kmmio.c b/arch/x86/mm/kmmio.c
index 4c66bd3a240d..9f205030d9aa 100644
--- a/arch/x86/mm/kmmio.c
+++ b/arch/x86/mm/kmmio.c
@@ -38,7 +38,8 @@ struct kmmio_fault_page {
         /*
          * Number of times this page has been registered as a part
          * of a probe. If zero, page is disarmed and this may be freed.
-         * Used only by writers (RCU).
+         * Used only by writers (RCU) and post_kmmio_handler().
+         * Protected by kmmio_lock, when linked into kmmio_page_table.
          */
         int count;
 };
@@ -317,7 +318,11 @@ static int post_kmmio_handler(unsigned long condition, struct pt_regs *regs)
         if (ctx->probe && ctx->probe->post_handler)
                 ctx->probe->post_handler(ctx->probe, condition, regs);
 
-        arm_kmmio_fault_page(ctx->fpage);
+        /* Prevent racing against release_kmmio_fault_page(). */
+        spin_lock(&kmmio_lock);
+        if (ctx->fpage->count)
+                arm_kmmio_fault_page(ctx->fpage);
+        spin_unlock(&kmmio_lock);
 
         regs->flags &= ~X86_EFLAGS_TF;
         regs->flags |= ctx->saved_flags;