git: f13da24715a7 - main - net/bpf: Fix writing of buffer bigger than PAGESIZE

[Gleb Smirnoff]

  Warner, Kristof,

On Wed, Jun 23, 2021 at 04:41:01PM +0000, Warner Losh wrote:
W>     net/bpf: Fix writing of buffer bigger than PAGESIZE
W>     
W>     When allocating the mbuf we used m_get2 which fails
W>     if len is superior to MJUMPAGESIZE, if its the case,
W>     use m_getjcl instead.
W>     
W>     Reviewed by:    kp@
W>     PR:             205164
W>     Pull Request:   https://github.com/freebsd/freebsd-src/pull/131

m_get2() used to provide jumbo mbufs in the past, see 3112ae76449ae0931d207603f14b083627bd731d.

IMHO, makes sense to create m_get3() and use it in bpf. What do you think?

W> @@ -641,7 +641,15 @@ bpf_movein(struct uio *uio, int linktype, struct ifnet *ifp, struct mbuf **mp,
W>  	if (len < hlen || len - hlen > ifp->if_mtu)
W>  		return (EMSGSIZE);
W>  
W> -	m = m_get2(len, M_WAITOK, MT_DATA, M_PKTHDR);
W> +	/* Allocate a mbuf for our write, since m_get2 fails if len >= to MJUMPAGESIZE, use m_getjcl for bigger buffers */
W> +	if (len < MJUMPAGESIZE)
W> +		m = m_get2(len, M_WAITOK, MT_DATA, M_PKTHDR);
W> +	else if (len <= MJUM9BYTES)
W> +		m = m_getjcl(M_WAITOK, MT_DATA, M_PKTHDR, MJUM9BYTES);
W> +	else if (len <= MJUM16BYTES)
W> +		m = m_getjcl(M_WAITOK, MT_DATA, M_PKTHDR, MJUM16BYTES);
W> +	else
W> +		m = NULL;
W>  	if (m == NULL)
W>  		return (EIO);
W>  	m->m_pkthdr.len = m->m_len = len;

-- 
Gleb Smirnoff