diff mbox series

[v3,37/46] x86: kmsan: make READ_ONCE_TASK_STACK() return initialized values

Message ID 20220426164315.625149-38-glider@google.com (mailing list archive)
State New
Headers show
Series Add KernelMemorySanitizer infrastructure | expand

Commit Message

Alexander Potapenko April 26, 2022, 4:43 p.m. UTC 
To avoid false positives, assume that reading from the task stack
always produces initialized values.

Signed-off-by: Alexander Potapenko <glider@google.com>
---
Link: https://linux-review.googlesource.com/id/I9e2350bf3e88688dd83537e12a23456480141997
---
 arch/x86/include/asm/unwind.h | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)
diff mbox series

Patch

diff --git a/arch/x86/include/asm/unwind.h b/arch/x86/include/asm/unwind.h
index 7cede4dc21f00..87acc90875b74 100644
--- a/arch/x86/include/asm/unwind.h
+++ b/arch/x86/include/asm/unwind.h
@@ -128,18 +128,19 @@  unsigned long unwind_recover_ret_addr(struct unwind_state *state,
 }
 
 /*
- * This disables KASAN checking when reading a value from another task's stack,
- * since the other task could be running on another CPU and could have poisoned
- * the stack in the meantime.
+ * This disables KASAN/KMSAN checking when reading a value from another task's
+ * stack, since the other task could be running on another CPU and could have
+ * poisoned the stack in the meantime. Frame pointers are uninitialized by
+ * default, so for KMSAN we mark the return value initialized unconditionally.
  */
-#define READ_ONCE_TASK_STACK(task, x)			\
-({							\
-	unsigned long val;				\
-	if (task == current)				\
-		val = READ_ONCE(x);			\
-	else						\
-		val = READ_ONCE_NOCHECK(x);		\
-	val;						\
+#define READ_ONCE_TASK_STACK(task, x)				\
+({								\
+	unsigned long val;					\
+	if (task == current && !IS_ENABLED(CONFIG_KMSAN))	\
+		val = READ_ONCE(x);				\
+	else							\
+		val = READ_ONCE_NOCHECK(x);			\
+	val;							\
 })
 
 static inline bool task_on_another_cpu(struct task_struct *task)