From: Cong Wang xiyou.wangcong@gmail.com
stable inclusion from linux-4.19.153 commit 26217e062f976fc4e2b7b8b6981a6d119435ea51
--------------------------------
[ Upstream commit ed42989eab57d619667d7e87dfbd8fe207db54fe ]
skb_unshare() drops a reference count on the old skb unconditionally, so in the failure case, we end up freeing the skb twice here. And because the skb is allocated in fclone and cloned by caller tipc_msg_reassemble(), the consequence is actually freeing the original skb too, thus triggered the UAF by syzbot.
Fix this by replacing this skb_unshare() with skb_cloned()+skb_copy().
Fixes: ff48b6222e65 ("tipc: use skb_unshare() instead in tipc_buf_append()") Reported-and-tested-by: syzbot+e96a7ba46281824cc46a@syzkaller.appspotmail.com Cc: Jon Maloy jmaloy@redhat.com Cc: Ying Xue ying.xue@windriver.com Signed-off-by: Cong Wang xiyou.wangcong@gmail.com Reviewed-by: Xin Long lucien.xin@gmail.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Yang Yingliang yangyingliang@huawei.com
Signed-off-by: Aichun Li liaichun@huawei.com Reviewed-by: wangxiaopeng wangxiaopeng7@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- net/tipc/msg.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/net/tipc/msg.c b/net/tipc/msg.c index b078b77620f1..0b8446cd541c 100644 --- a/net/tipc/msg.c +++ b/net/tipc/msg.c @@ -140,7 +140,8 @@ int tipc_buf_append(struct sk_buff **headbuf, struct sk_buff **buf) if (fragid == FIRST_FRAGMENT) { if (unlikely(head)) goto err; - frag = skb_unshare(frag, GFP_ATOMIC); + if (skb_cloned(frag)) + frag = skb_copy(frag, GFP_ATOMIC); if (unlikely(!frag)) goto err; head = *headbuf = frag;