diff options
| author | Willem de Bruijn <willemb@google.com> | 2017-12-28 20:38:13 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-01-02 22:31:13 +0300 |
| commit | b9edd6bf0ccb2939a7716b80d3e73a24ead9fe62 (patch) | |
| tree | fec700c00050e98551ccae46fa1cf31865413fc6 /net/core | |
| parent | 49cd180d4a104159f240a9a896e5f13844227378 (diff) | |
| download | linux-b9edd6bf0ccb2939a7716b80d3e73a24ead9fe62.tar.xz | |
skbuff: in skb_copy_ubufs unclone before releasing zerocopy
skb_copy_ubufs must unclone before it is safe to modify its
skb_shared_info with skb_zcopy_clear.
Commit b90ddd568792 ("skbuff: skb_copy_ubufs must release uarg even
without user frags") ensures that all skbs release their zerocopy
state, even those without frags.
But I forgot an edge case where such an skb arrives that is cloned.
The stack does not build such packets. Vhost/tun skbs have their
frags orphaned before cloning. TCP skbs only attach zerocopy state
when a frag is added.
But if TCP packets can be trimmed or linearized, this might occur.
Tracing the code I found no instance so far (e.g., skb_linearize
ends up calling skb_zcopy_clear if !skb->data_len).
Still, it is non-obvious that no path exists. And it is fragile to
rely on this.
Fixes: b90ddd568792 ("skbuff: skb_copy_ubufs must release uarg even without user frags")
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'net/core')
| -rw-r--r-- | net/core/skbuff.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 4a10e96c6efc..15fa5baa8fae 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -1181,12 +1181,12 @@ int skb_copy_ubufs(struct sk_buff *skb, gfp_t gfp_mask) int i, new_frags; u32 d_off; - if (!num_frags) - goto release; - if (skb_shared(skb) || skb_unclone(skb, gfp_mask)) return -EINVAL; + if (!num_frags) + goto release; + new_frags = (__skb_pagelen(skb) + PAGE_SIZE - 1) >> PAGE_SHIFT; for (i = 0; i < new_frags; i++) { page = alloc_page(gfp_mask); |