[PATCH 4/7] x86: mtrr: Abort if requested size is not power of 2

[Bin Meng]

The size parameter of mtrr_add_request() and mtrr_set_next_var()
shall be power of 2, otherwise the logic creates a mask that does
not meet the requirement of IA32_MTRR_PHYSMASK register.

Programming such a mask value to IA32_MTRR_PHYSMASK generates #GP.

Signed-off-by: Bin Meng <bmeng.cn at gmail.com>
---

 arch/x86/cpu/mtrr.c         | 7 +++++++
 arch/x86/include/asm/mtrr.h | 7 ++++---
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/arch/x86/cpu/mtrr.c b/arch/x86/cpu/mtrr.c
index 14c644eb56..260a008093 100644
--- a/arch/x86/cpu/mtrr.c
+++ b/arch/x86/cpu/mtrr.c
@@ -26,6 +26,7 @@
 #include <asm/mp.h>
 #include <asm/msr.h>
 #include <asm/mtrr.h>
+#include <linux/log2.h>
 
 DECLARE_GLOBAL_DATA_PTR;
 
@@ -179,6 +180,9 @@ int mtrr_add_request(int type, uint64_t start, uint64_t size)
 	if (!gd->arch.has_mtrr)
 		return -ENOSYS;
 
+	if (!is_power_of_2(size))
+		return -EINVAL;
+
 	if (gd->arch.mtrr_req_count == MAX_MTRR_REQUESTS)
 		return -ENOSPC;
 	req = &gd->arch.mtrr_req[gd->arch.mtrr_req_count++];
@@ -223,6 +227,9 @@ int mtrr_set_next_var(uint type, uint64_t start, uint64_t size)
 {
 	int mtrr;
 
+	if (!is_power_of_2(size))
+		return -EINVAL;
+
 	mtrr = get_free_var_mtrr();
 	if (mtrr < 0)
 		return mtrr;
diff --git a/arch/x86/include/asm/mtrr.h b/arch/x86/include/asm/mtrr.h
index 384672e93f..d1aa86bf1d 100644
--- a/arch/x86/include/asm/mtrr.h
+++ b/arch/x86/include/asm/mtrr.h
@@ -119,7 +119,7 @@ void mtrr_close(struct mtrr_state *state, bool do_caches);
  *
  * @type:	Requested type (MTRR_TYPE_)
  * @start:	Start address
- * @size:	Size
+ * @size:	Size, must be power of 2
  *
  * @return:	0 on success, non-zero on failure
  */
@@ -144,8 +144,9 @@ int mtrr_commit(bool do_caches);
  *
  * @type:	Requested type (MTRR_TYPE_)
  * @start:	Start address
- * @size:	Size
- * @return 0 on success, -ENOSPC if there are no more MTRRs
+ * @size:	Size, must be power of 2
+ * @return 0 on success, -EINVAL if size is not power of 2,
+ * -ENOSPC if there are no more MTRRs
  */
 int mtrr_set_next_var(uint type, uint64_t base, uint64_t size);
 
-- 
2.25.1