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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>
This commit is contained in:
Jon Paul Maloy 2014-07-25 14:48:09 -04:00 committed by David S. Miller
parent 3fd0202a0d
commit 13e9b9972f
1 changed files with 21 additions and 8 deletions
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29
net/tipc/msg.c
View File

@ -72,27 +72,38 @@ int tipc_buf_append(struct sk_buff **headbuf, struct sk_buff **buf)
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 @@ int tipc_buf_append(struct sk_buff **headbuf, struct sk_buff **buf)
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 @@ int tipc_buf_append(struct sk_buff **headbuf, struct sk_buff **buf)
}
*buf = NULL;
return 0;
out_free:
err:
pr_warn_ratelimited("Unable to build fragment list\n");
kfree_skb(*buf);
kfree_skb(*headbuf);