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>

diff --git a/ipc/msgutil.c b/ipc/msgutil.c
index 0a5c8a95c2576e45490b54be118d740bfccbd82c..b79582d461a458e9ddf0cbc0669da0c346653fb0 100644 (file)
--- 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;
 }