P J P <ppan...@redhat.com> writes:
> From: Prasad J Pandit <p...@fedoraproject.org>
>
> While computing IP checksum, 'net_checksum_calculate' reads
> payload length from the packet. It could exceed the given 'data'
> buffer size. Add a check to avoid it.
>
> Reported-by: Liu Ling <liuling...@360.cn>
> Signed-off-by: Prasad J Pandit <p...@fedoraproject.org>
> ---
> net/checksum.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/net/checksum.c b/net/checksum.c
> index 14c0855..e51698c 100644
> --- a/net/checksum.c
> +++ b/net/checksum.c
> @@ -76,8 +76,9 @@ void net_checksum_calculate(uint8_t *data, int length)
> return;
> }
>
> - if (plen < csum_offset+2)
> - return;
> + if ((plen < csum_offset + 2) || (plen + hlen >= length)) {
> + return;
> + }
>
> data[14+hlen+csum_offset] = 0;
> data[14+hlen+csum_offset+1] = 0;
Function takes data + length, then doesn't use length *groan*.
The function stores the checksum if
* this is an IPv4 TCP or UDP packet, and
* the packet is long enough to include the checksum (but may still be
shorter than the TCP header), and
* (new with your patch) the buffer holds the complete packet
Else it does nothing.
Doing nothing for packets other than IPv4 TCP/UDP is obviously
intentional.
Is calling this function with a partial IPv4 TCP/UDP packet legitimate?
If not, should we assert plen + hlen <= length? Or == length, even?
If partial packet is okay, what about a partial header?
If either is legit, are the callers that can do it prepared for the
checksum not to be computed?
Style nitpick: we generally omit obviously superfluous parenthesis.
