tipc: make tipc_buf_append() more robust
As per comment from David Miller, we try to make the buffer reassembly
function more resilient to user errors than it is today.
- We check that the "*buf" parameter always is set, since this is
mandatory input.
- We ensure that *buf->next always is set to NULL before linking in
the buffer, instead of relying of the caller to have done this.
- We ensure that the "tail" pointer in the head buffer's control
block is initialized to NULL when the first fragment arrives.
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/tipc/msg.c b/net/tipc/msg.c
index b6f45d0..9680be6 100644
--- a/net/tipc/msg.c
+++ b/net/tipc/msg.c
@@ -72,27 +72,38 @@
struct sk_buff *head = *headbuf;
struct sk_buff *frag = *buf;
struct sk_buff *tail;
- struct tipc_msg *msg = buf_msg(frag);
- u32 fragid = msg_type(msg);
- bool headstolen;
+ struct tipc_msg *msg;
+ u32 fragid;
int delta;
+ bool headstolen;
+ if (!frag)
+ goto err;
+
+ msg = buf_msg(frag);
+ fragid = msg_type(msg);
+ frag->next = NULL;
skb_pull(frag, msg_hdr_sz(msg));
if (fragid == FIRST_FRAGMENT) {
- if (head || skb_unclone(frag, GFP_ATOMIC))
- goto out_free;
+ if (unlikely(head))
+ goto err;
+ if (unlikely(skb_unclone(frag, GFP_ATOMIC)))
+ goto err;
head = *headbuf = frag;
skb_frag_list_init(head);
+ TIPC_SKB_CB(head)->tail = NULL;
*buf = NULL;
return 0;
}
+
if (!head)
- goto out_free;
- tail = TIPC_SKB_CB(head)->tail;
+ goto err;
+
if (skb_try_coalesce(head, frag, &headstolen, &delta)) {
kfree_skb_partial(frag, headstolen);
} else {
+ tail = TIPC_SKB_CB(head)->tail;
if (!skb_has_frag_list(head))
skb_shinfo(head)->frag_list = frag;
else
@@ -102,6 +113,7 @@
head->len += frag->len;
TIPC_SKB_CB(head)->tail = frag;
}
+
if (fragid == LAST_FRAGMENT) {
*buf = head;
TIPC_SKB_CB(head)->tail = NULL;
@@ -110,7 +122,8 @@
}
*buf = NULL;
return 0;
-out_free:
+
+err:
pr_warn_ratelimited("Unable to build fragment list\n");
kfree_skb(*buf);
kfree_skb(*headbuf);