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| author | Jason Wang <jasowang@redhat.com> | 2013-11-13 14:00:39 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2013-12-08 07:29:12 -0800 |
| commit | d485b5173b10de877781e6cabf39bee3f0bca5dc (patch) | |
| tree | 371e3ea01cb336db141839249a581d9a6ae97ed9 /drivers | |
| parent | cec2b41aaf8da29ca3bb2a56a1cd67c6675ed60f (diff) | |
| download | lwn-d485b5173b10de877781e6cabf39bee3f0bca5dc.tar.gz lwn-d485b5173b10de877781e6cabf39bee3f0bca5dc.zip | |
tuntap: limit head length of skb allocated
[ Upstream commit 96f8d9ecf227638c89f98ccdcdd50b569891976c ]
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 <stefanha@redhat.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/net/tun.c | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/drivers/net/tun.c b/drivers/net/tun.c index 7cb105c103fe..782e38bfc1ee 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -981,6 +981,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile, struct sk_buff *skb; size_t len = total_len, align = NET_SKB_PAD, linear; struct virtio_net_hdr gso = { 0 }; + int good_linear; int offset = 0; int copylen; bool zerocopy = false; @@ -1021,12 +1022,16 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile, return -EINVAL; } + good_linear = SKB_MAX_HEAD(align); + if (msg_control) { /* There are 256 bytes to be copied in skb, so there is * enough room for skb expand head in case it is used. * The rest of the buffer is mapped from userspace. */ copylen = gso.hdr_len ? gso.hdr_len : GOODCOPY_LEN; + if (copylen > good_linear) + copylen = good_linear; linear = copylen; if (iov_pages(iv, offset + copylen, count) <= MAX_SKB_FRAGS) zerocopy = true; @@ -1034,7 +1039,10 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile, if (!zerocopy) { copylen = len; - linear = gso.hdr_len; + if (gso.hdr_len > good_linear) + linear = good_linear; + else + linear = gso.hdr_len; } skb = tun_alloc_skb(tfile, align, copylen, linear, noblock); |