mm, kmsan: fix infinite recursion due to RCU critical section

[platform/kernel/linux-starfive.git] / arch / x86 / include / asm / kmsan.h

diff --git a/arch/x86/include/asm/kmsan.h b/arch/x86/include/asm/kmsan.h
index 8fa6ac0..d91b37f 100644 (file)
--- a/arch/x86/include/asm/kmsan.h
+++ b/arch/x86/include/asm/kmsan.h
@@ -64,6 +64,7 @@ static inline bool kmsan_virt_addr_valid(void *addr)
 {
        unsigned long x = (unsigned long)addr;
        unsigned long y = x - __START_KERNEL_map;
+       bool ret;
 
        /* use the carry flag to determine if x was < __START_KERNEL_map */
        if (unlikely(x > y)) {
@@ -79,7 +80,21 @@ static inline bool kmsan_virt_addr_valid(void *addr)
                        return false;
        }
 
-       return pfn_valid(x >> PAGE_SHIFT);
+       /*
+        * pfn_valid() relies on RCU, and may call into the scheduler on exiting
+        * the critical section. However, this would result in recursion with
+        * KMSAN. Therefore, disable preemption here, and re-enable preemption
+        * below while suppressing reschedules to avoid recursion.
+        *
+        * Note, this sacrifices occasionally breaking scheduling guarantees.
+        * Although, a kernel compiled with KMSAN has already given up on any
+        * performance guarantees due to being heavily instrumented.
+        */
+       preempt_disable();
+       ret = pfn_valid(x >> PAGE_SHIFT);
+       preempt_enable_no_resched();
+
+       return ret;
 }
 
 #endif /* !MODULE */