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Subject[029/136] perf_counter: Fix perf_copy_attr() pointer arithmetic
2.6.31-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Ian Schram <ischram@telenet.be>

commit cdf8073d6b2c6c5a3cd6ce0e6c1297157f7f99ba upstream.

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>
LKML-Reference: <4AB3DEE2.3030600@telenet.be>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
kernel/perf_counter.c | 22 +++++++++++-----------
1 file changed, 11 insertions(+), 11 deletions(-)

--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -4143,8 +4143,8 @@ 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;
@@ -4169,19 +4169,19 @@ static int perf_copy_attr(struct perf_co

/*
* 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;
-
- addr = PTR_ALIGN((void __user *)uattr + sizeof(*attr),
- sizeof(unsigned long));
- end = PTR_ALIGN((void __user *)uattr + size,
- sizeof(unsigned long));
+ unsigned char __user *addr;
+ unsigned char __user *end;
+ unsigned char val;
+
+ 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;



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