Re: [PATCH net] udp: fix linear skb reception with PEEK_OFF

[Eric Dumazet <eric.dumazet@gmail.com>]

On Mon, 2017-08-14 at 21:31 +0200, Paolo Abeni wrote:
> From: Al Viro <viro@ZenIV.linux.org.uk>
> 
> copy_linear_skb() is broken; both of its callers actually
> expect 'len' to be the amount we are trying to copy,
> not the offset of the end.
> Fix it keeping the meanings of arguments in sync with what the
> callers (both of them) expect.
> Also restore a saner behavior on EFAULT (i.e. preserving
> the iov_iter position in case of failure):
> 
> The commit fd851ba9caa9 ("udp: harden copy_linear_skb()")
> avoids the more destructive effect of the buggy
> copy_linear_skb(), e.g. no more invalid memory access, but
> said function still behaves incorrectly: when peeking with
> offset it can fail with EINVAL instead of copying the
> appropriate amount of memory.
> 
> Reported-by: Sasha Levin <alexander.levin@verizon.com>
> Fixes: b65ac44674dd ("udp: try to avoid 2 cache miss on dequeue")
> Fixes: fd851ba9caa9 ("udp: harden copy_linear_skb()")
> Signed-off-by: Al Viro <viro@ZenIV.linux.org.uk>
> Acked-by: Paolo Abeni <pabeni@redhat.com>
> Tested-by: Sasha Levin <alexander.levin@verizon.com>
> ---

Oh well.

Acked-by: Eric Dumazet <edumazet@google.com>