diff options
| author | Willem de Bruijn <willemb@google.com> | 2017-12-28 12:38:13 -0500 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2017-12-28 14:26:22 -0500 |
| commit | f72c4ac695573699dde5b71da1c3b9ef80440616 (patch) | |
| tree | 0c2ec556c1218b9dafcbbaa8c2906082d7d8b6f1 | |
| parent | 517d7c79bdb39864e617960504bdc1aa560c75c6 (diff) | |
| download | linux-f72c4ac695573699dde5b71da1c3b9ef80440616.tar.bz2 | |
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>
| -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 a3cb0be4c6f3..08f574081315 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -1177,12 +1177,12 @@ 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); |