diff options
| author | Eric Dumazet <edumazet@google.com> | 2017-01-27 07:11:27 -0800 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2017-01-27 12:03:29 -0500 |
| commit | 158f323b9868b59967ad96957c4ca388161be321 (patch) | |
| tree | 507829772e7f0849038baf503f85fe788b0e4340 /net/core/skbuff.c | |
| parent | b41fd8fdef5ad4a1dbd2a159714bd4358bb49625 (diff) | |
net: adjust skb->truesize in pskb_expand_head()
Slava Shwartsman reported a warning in skb_try_coalesce(), when we
detect skb->truesize is completely wrong.
In his case, issue came from IPv6 reassembly coping with malicious
datagrams, that forced various pskb_may_pull() to reallocate a bigger
skb->head than the one allocated by NIC driver before entering GRO
layer.
Current code does not change skb->truesize, leaving this burden to
callers if they care enough.
Blindly changing skb->truesize in pskb_expand_head() is not
easy, as some producers might track skb->truesize, for example
in xmit path for back pressure feedback (sk->sk_wmem_alloc)
We can detect the cases where it should be safe to change
skb->truesize :
1) skb is not attached to a socket.
2) If it is attached to a socket, destructor is sock_edemux()
My audit gave only two callers doing their own skb->truesize
manipulation.
I had to remove skb parameter in sock_edemux macro when
CONFIG_INET is not set to avoid a compile error.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Slava Shwartsman <slavash@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/core/skbuff.c')
| -rw-r--r-- | net/core/skbuff.c | 14 |
1 files changed, 11 insertions, 3 deletions
diff --git a/net/core/skbuff.c b/net/core/skbuff.c index f8dbe4a7ab46..26c1344cc23e 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -1192,10 +1192,10 @@ EXPORT_SYMBOL(__pskb_copy_fclone); int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail, gfp_t gfp_mask) { - int i; - u8 *data; - int size = nhead + skb_end_offset(skb) + ntail; + int i, osize = skb_end_offset(skb); + int size = osize + nhead + ntail; long off; + u8 *data; BUG_ON(nhead < 0); @@ -1257,6 +1257,14 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail, skb->hdr_len = 0; skb->nohdr = 0; atomic_set(&skb_shinfo(skb)->dataref, 1); + + /* It is not generally safe to change skb->truesize. + * For the moment, we really care of rx path, or + * when skb is orphaned (not attached to a socket). + */ + if (!skb->sk || skb->destructor == sock_edemux) + skb->truesize += size - osize; + return 0; nofrags: |