perf_counter: Fix perf_copy_attr() pointer arithmetic

There is still some weird code in per_copy_attr(). Which supposedly
checks that all bytes trailing a struct are zero.

It doesn't seem to get pointer arithmetic right. Since it
increments an iterating pointer by sizeof(unsigned long) rather
than 1.

Signed-off-by: Ian Schram <ischram@telenet.be>
[ v2: clean up the messy PTR_ALIGN logic as well. ]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: <stable@kernel.org> # for v2.6.31.x
LKML-Reference: <4AB3DEE2.3030600@telenet.be>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 10 insertions, 10 deletions

diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index d5899b62b27..cc768ab81ac 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -4208,8 +4208,8 @@ done:
 static int perf_copy_attr(struct perf_counter_attr __user *uattr,
                           struct perf_counter_attr *attr)
 {
-        int ret;
         u32 size;
+        int ret;
 
         if (!access_ok(VERIFY_WRITE, uattr, PERF_ATTR_SIZE_VER0))
                 return -EFAULT;
@@ -4234,19 +4234,19 @@ static int perf_copy_attr(struct perf_counter_attr __user *uattr,
 
         /*
          * If we're handed a bigger struct than we know of,
-         * ensure all the unknown bits are 0.
+         * ensure all the unknown bits are 0 - i.e. new
+         * user-space does not rely on any kernel feature
+         * extensions we dont know about yet.
          */
         if (size > sizeof(*attr)) {
-                unsigned long val;
-                unsigned long __user *addr;
-                unsigned long __user *end;
+                unsigned char __user *addr;
+                unsigned char __user *end;
+                unsigned char val;
 
-                addr = PTR_ALIGN((void __user *)uattr + sizeof(*attr),
-                                sizeof(unsigned long));
-                end  = PTR_ALIGN((void __user *)uattr + size,
-                                sizeof(unsigned long));
+                addr = (void __user *)uattr + sizeof(*attr);
+                end  = (void __user *)uattr + size;
 
-                for (; addr < end; addr += sizeof(unsigned long)) {
+                for (; addr < end; addr++) {
                         ret = get_user(val, addr);
                         if (ret)
                                 return ret;