ipc: tighten msg copy loops

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Acked-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 11 insertions, 21 deletions

diff --git a/ipc/msgutil.c b/ipc/msgutil.c
index 0a5c8a95c257..b79582d461a4 100644
--- a/ipc/msgutil.c
+++ b/ipc/msgutil.c
@@ -97,18 +97,14 @@ struct msg_msg *load_msg(const void __user *src, int len)
                 goto out_err;
         }
 
-        len -= alen;
-        src = ((char __user *)src) + alen;
-        seg = msg->next;
-        while (len > 0) {
+        for (seg = msg->next; seg != NULL; seg = seg->next) {
+                len -= alen;
+                src = (char __user *)src + alen;
                 alen = min(len, DATALEN_SEG);
                 if (copy_from_user(seg + 1, src, alen)) {
                         err = -EFAULT;
                         goto out_err;
                 }
-                seg = seg->next;
-                len -= alen;
-                src = ((char __user *)src) + alen;
         }
 
         err = security_msg_msg_alloc(msg);
@@ -135,15 +131,13 @@ struct msg_msg *copy_msg(struct msg_msg *src, struct msg_msg *dst)
         alen = min(len, DATALEN_MSG);
         memcpy(dst + 1, src + 1, alen);
 
-        len -= alen;
-        dst_pseg = dst->next;
-        src_pseg = src->next;
-        while (len > 0) {
+        for (dst_pseg = dst->next, src_pseg = src->next;
+             src_pseg != NULL;
+             dst_pseg = dst_pseg->next, src_pseg = src_pseg->next) {
+
+                len -= alen;
                 alen = min(len, DATALEN_SEG);
                 memcpy(dst_pseg + 1, src_pseg + 1, alen);
-                dst_pseg = dst_pseg->next;
-                len -= alen;
-                src_pseg = src_pseg->next;
         }
 
         dst->m_type = src->m_type;
@@ -166,16 +160,12 @@ int store_msg(void __user *dest, struct msg_msg *msg, int len)
         if (copy_to_user(dest, msg + 1, alen))
                 return -1;
 
-        len -= alen;
-        dest = ((char __user *)dest) + alen;
-        seg = msg->next;
-        while (len > 0) {
+        for (seg = msg->next; seg != NULL; seg = seg->next) {
+                len -= alen;
+                dest = (char __user *)dest + alen;
                 alen = min(len, DATALEN_SEG);
                 if (copy_to_user(dest, seg + 1, alen))
                         return -1;
-                len -= alen;
-                dest = ((char __user *)dest) + alen;
-                seg = seg->next;
         }
         return 0;
 }