Hello,
this patchset fixes three things in skbuff handling:
1) Current implementation of 'virtio_transport_dec_rx_pkt()':
value to update 'rx_bytes' and 'fwd_cnt' is calculated as:
skb_headroom(skb) - sizeof(struct virtio_vsock_hdr) - skb->len;
i'm a little bit confused about subtracting 'skb->len'. It is clear,
that difference between first two components is number of bytes copied
to user. 'skb_headroom()' is delta between 'data' and 'head'. 'data'
is incremented on each copy data to user from skb by call 'skb_pull()'
(at the same moment, 'skb->len' is decremented to the same amount of
bytes). 'head' points to the header of the packet. But what is purpose
of 'skb->len' here? For SOCK_STREAM is has no effect because this
logic is called only when 'skb->len' == 0, but for SOCK_SEQPACKET and
other future calls i think it is buggy.
2) For SOCK_SEQPACKET all sk_buffs are handled only once - after dequeue
each sk_buff is removed, so user will never read rest of the data.
Thus we need to update credit parameters of the socket ('rx_bytes' and
'fwd_cnt') like whole sk_buff is read - so call 'skb_pull()' for the
whole buffer.
3) For SOCK_STREAM when 'memcpy_to_msg()' fails it fixes 'rx_bytes'
update (like in 2)) and frees current skbuff.
Test is also added to vsock_test. It does two attempts to read data from
socket - first attempt to invalid buffer (kernel must drop skb). Second
attempt is performed with valid buffer and MSG_DONTWAIT flag. If socket's
queue will be empty (skbuff was dropped due to 'memcpy_to_msg()' fail
and 'rx_bytes' which controls data waiting set to 0), such call will
return immediately with EAGAIN.
Link to v1 on lore:
https://lore.kernel.org/netdev/c2d3e204-89d9-88e9-8a15-3fe027e56b4b@xxxxxxxxxxxxxx/
Change log:
v1 -> v2:
- For SOCK_SEQPACKET call 'skb_pull()' also in case of copy failure or
dropping skbuff (when we just waiting message end).
- Handle copy failure for SOCK_STREAM in the same manner (plus free
current skbuff).
- Replace bug repdroducer with new test in vsock_test.c
Arseniy Krasnov (4):
virtio/vsock: fix 'rx_bytes'/'fwd_cnt' calculation
virtio/vsock: remove all data from sk_buff
virtio/vsock: free skb on data copy failure
test/vsock: invalid buffer tests
net/vmw_vsock/virtio_transport_common.c | 10 ++-
tools/testing/vsock/vsock_test.c | 106 ++++++++++++++++++++++++
2 files changed, 113 insertions(+), 3 deletions(-)
--
2.25.1
