From: Carl Huang cjhuang@codeaurora.org
commit ce57785bf91b1ceaef4f4bffed8a47dc0919c8da upstream.
The len used for skb_put_padto is wrong, it need to add len of hdr.
In qrtr_node_enqueue, local variable size_t len is assign with skb->len, then skb_push(skb, sizeof(*hdr)) will add skb->len with sizeof(*hdr), so local variable size_t len is not same with skb->len after skb_push(skb, sizeof(*hdr)).
Then the purpose of skb_put_padto(skb, ALIGN(len, 4)) is to add add pad to the end of the skb's data if skb->len is not aligned to 4, but unfortunately it use len instead of skb->len, at this line, skb->len is 32 bytes(sizeof(*hdr)) more than len, for example, len is 3 bytes, then skb->len is 35 bytes(3 + 32), and ALIGN(len, 4) is 4 bytes, so __skb_put_padto will do nothing after check size(35) < len(4), the correct value should be 36(sizeof(*hdr) + ALIGN(len, 4) = 32 + 4), then __skb_put_padto will pass check size(35) < len(36) and add 1 byte to the end of skb's data, then logic is correct.
function of skb_push: void *skb_push(struct sk_buff *skb, unsigned int len) { skb->data -= len; skb->len += len; if (unlikely(skb->data < skb->head)) skb_under_panic(skb, len, __builtin_return_address(0)); return skb->data; }
function of skb_put_padto static inline int skb_put_padto(struct sk_buff *skb, unsigned int len) { return __skb_put_padto(skb, len, true); }
function of __skb_put_padto static inline int __skb_put_padto(struct sk_buff *skb, unsigned int len, bool free_on_error) { unsigned int size = skb->len;
if (unlikely(size < len)) { len -= size; if (__skb_pad(skb, len, free_on_error)) return -ENOMEM; __skb_put(skb, len); } return 0; }
Signed-off-by: Carl Huang cjhuang@codeaurora.org Signed-off-by: Wen Gong wgong@codeaurora.org Cc: Doug Anderson dianders@chromium.org Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- net/qrtr/qrtr.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/net/qrtr/qrtr.c +++ b/net/qrtr/qrtr.c @@ -196,7 +196,7 @@ static int qrtr_node_enqueue(struct qrtr hdr->size = cpu_to_le32(len); hdr->confirm_rx = 0;
- skb_put_padto(skb, ALIGN(len, 4)); + skb_put_padto(skb, ALIGN(len, 4) + sizeof(*hdr));
mutex_lock(&node->ep_lock); if (node->ep)