We currently use hdr_len as a hint of head length which is advertised by guest. But when guest advertise a very big value, it can lead to an 64K+ allocating of kmalloc() which has a very high possibility of failure when host memory is fragmented or under heavy stress. The huge hdr_len also reduce the effect of zerocopy or even disable if a gso skb is linearized in guest.
To solves those issues, this patch introduces an upper limit (PAGE_SIZE) of the head, which guarantees an order 0 allocation each time. Cc: Stefan Hajnoczi <stefa...@redhat.com> Cc: Michael S. Tsirkin <m...@redhat.com> Signed-off-by: Jason Wang <jasow...@redhat.com> --- The patch was needed for stable. --- drivers/net/tun.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/net/tun.c b/drivers/net/tun.c index 7cb105c..5537b65 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -954,6 +954,11 @@ static struct sk_buff *tun_alloc_skb(struct tun_file *tfile, struct sock *sk = tfile->socket.sk; struct sk_buff *skb; int err; + int good_linear = SKB_MAX_HEAD(prepad); + + /* Don't use huge linear part */ + if (linear > good_linear) + linear = good_linear; /* Under a page? Don't bother with paged skb. */ if (prepad + len < PAGE_SIZE || !linear) -- 1.8.3.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/