1 files changed, 9 insertions, 37 deletions

diff --git a/arch/arm/oprofile/backtrace.c b/arch/arm/oprofile/backtrace.c
index df35c452a8bf..7c22c12618cc 100644
--- a/arch/arm/oprofile/backtrace.c
+++ b/arch/arm/oprofile/backtrace.c
@@ -49,42 +49,22 @@ static struct frame_tail* kernel_backtrace(struct frame_tail *tail)
 
 static struct frame_tail* user_backtrace(struct frame_tail *tail)
 {
-        struct frame_tail buftail;
+        struct frame_tail buftail[2];
 
-        /* hardware pte might not be valid due to dirty/accessed bit emulation
-         * so we use copy_from_user and benefit from exception fixups */
-        if (copy_from_user(&buftail, tail, sizeof(struct frame_tail)))
+        /* Also check accessibility of one struct frame_tail beyond */
+        if (!access_ok(VERIFY_READ, tail, sizeof(buftail)))
+                return NULL;
+        if (__copy_from_user_inatomic(buftail, tail, sizeof(buftail)))
                 return NULL;
 
-        oprofile_add_trace(buftail.lr);
+        oprofile_add_trace(buftail[0].lr);
 
         /* frame pointers should strictly progress back up the stack
          * (towards higher addresses) */
-        if (tail >= buftail.fp)
+        if (tail >= buftail[0].fp)
                 return NULL;
 
-        return buftail.fp-1;
-}
-
-/* Compare two addresses and see if they're on the same page */
-#define CMP_ADDR_EQUAL(x,y,offset) ((((unsigned long) x) >> PAGE_SHIFT) \
-        == ((((unsigned long) y) + offset) >> PAGE_SHIFT))
-
-/* check that the page(s) containing the frame tail are present */
-static int pages_present(struct frame_tail *tail)
-{
-        struct mm_struct * mm = current->mm;
-
-        if (!check_user_page_readable(mm, (unsigned long)tail))
-                return 0;
-
-        if (CMP_ADDR_EQUAL(tail, tail, 8))
-                return 1;
-
-        if (!check_user_page_readable(mm, ((unsigned long)tail) + 8))
-                return 0;
-
-        return 1;
+        return buftail[0].fp-1;
 }
 
 /*
@@ -118,7 +98,6 @@ static int valid_kernel_stack(struct frame_tail *tail, struct pt_regs *regs)
 void arm_backtrace(struct pt_regs * const regs, unsigned int depth)
 {
         struct frame_tail *tail;
-        unsigned long last_address = 0;
 
         tail = ((struct frame_tail *) regs->ARM_fp) - 1;
 
@@ -132,13 +111,6 @@ void arm_backtrace(struct pt_regs * const regs, unsigned int depth)
                 return;
         }
 
-        while (depth-- && tail && !((unsigned long) tail & 3)) {
-                if ((!CMP_ADDR_EQUAL(last_address, tail, 0)
-                        || !CMP_ADDR_EQUAL(last_address, tail, 8))
-                                && !pages_present(tail))
-                        return;
-                last_address = (unsigned long) tail;
+        while (depth-- && tail && !((unsigned long) tail & 3))
                 tail = user_backtrace(tail);
-        }
 }
-