[029/136] perf_counter: Fix perf_copy_attr() pointer arithmetic

[Greg KH]

2.6.31-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Ian Schram <ischram@xxxxxxxxxx>

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@xxxxxxxxxx>
[ v2: clean up the messy PTR_ALIGN logic as well. ]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
LKML-Reference: <4AB3DEE2.3030600@xxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 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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