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[v2,39/48] x86: kmsan: make READ_ONCE_TASK_STACK() return initialized values

Message ID 20220329124017.737571-40-glider@google.com (mailing list archive)
State New
Headers show
Series Add KernelMemorySanitizer infrastructure | expand

Commit Message

Alexander Potapenko March 29, 2022, 12:40 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(-)
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Patch

diff --git a/arch/x86/include/asm/unwind.h b/arch/x86/include/asm/unwind.h
index 2a1f8734416dc..51173b19ac4d5 100644
--- a/arch/x86/include/asm/unwind.h
+++ b/arch/x86/include/asm/unwind.h
@@ -129,18 +129,19 @@  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)