CVE-2022-48819

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> tcp: take care of mixed splice()/sendmsg(MSG_ZEROCOPY) case<br /> <br /> syzbot found that mixing sendpage() and sendmsg(MSG_ZEROCOPY)<br /> calls over the same TCP socket would again trigger the<br /> infamous warning in inet_sock_destruct()<br /> <br /> WARN_ON(sk_forward_alloc_get(sk));<br /> <br /> While Talal took into account a mix of regular copied data<br /> and MSG_ZEROCOPY one in the same skb, the sendpage() path<br /> has been forgotten.<br /> <br /> We want the charging to happen for sendpage(), because<br /> pages could be coming from a pipe. What is missing is the<br /> downgrading of pure zerocopy status to make sure<br /> sk_forward_alloc will stay synced.<br /> <br /> Add tcp_downgrade_zcopy_pure() helper so that we can<br /> use it from the two callers.