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| author | Daniel Borkmann <daniel@iogearbox.net> | 2015-09-10 02:20:46 +0300 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2015-09-10 07:42:51 +0300 |
| commit | a66e36568e30ed3714c0e3a12bd3b64696343ff5 (patch) | |
| tree | 31f62f5e6258b1eaf5b7e7deede0dc8466031d17 /net/netlink/af_netlink.c | |
| parent | f2be053c83ee93888fc09d90df2bded0deb28947 (diff) | |
| download | linux-a66e36568e30ed3714c0e3a12bd3b64696343ff5.tar.xz | |
netlink, mmap: don't walk rx ring on poll if receive queue non-empty
In case of netlink mmap, there can be situations where received frames
have to be placed into the normal receive queue. The ring buffer indicates
this through NL_MMAP_STATUS_COPY, so the user is asked to pick them up
via recvmsg(2) syscall, and to put the slot back to NL_MMAP_STATUS_UNUSED.
Commit 0ef707700f1c ("netlink: rx mmap: fix POLLIN condition") changed
polling, so that we walk in the worst case the whole ring through the
new netlink_has_valid_frame(), for example, when the ring would have no
NL_MMAP_STATUS_VALID, but at least one NL_MMAP_STATUS_COPY frame.
Since we do a datagram_poll() already earlier to pick up a mask that could
possibly contain POLLIN | POLLRDNORM already (due to NL_MMAP_STATUS_COPY),
we can skip checking the rx ring entirely.
In case the kernel is compiled with !CONFIG_NETLINK_MMAP, then all this is
irrelevant anyway as netlink_poll() is just defined as datagram_poll().
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/netlink/af_netlink.c')
| -rw-r--r-- | net/netlink/af_netlink.c | 17 |
1 files changed, 12 insertions, 5 deletions
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c index 50889be1517d..173817a5dfad 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -674,12 +674,19 @@ static unsigned int netlink_poll(struct file *file, struct socket *sock, mask = datagram_poll(file, sock, wait); - spin_lock_bh(&sk->sk_receive_queue.lock); - if (nlk->rx_ring.pg_vec) { - if (netlink_has_valid_frame(&nlk->rx_ring)) - mask |= POLLIN | POLLRDNORM; + /* We could already have received frames in the normal receive + * queue, that will show up as NL_MMAP_STATUS_COPY in the ring, + * so if mask contains pollin/etc already, there's no point + * walking the ring. + */ + if ((mask & (POLLIN | POLLRDNORM)) != (POLLIN | POLLRDNORM)) { + spin_lock_bh(&sk->sk_receive_queue.lock); + if (nlk->rx_ring.pg_vec) { + if (netlink_has_valid_frame(&nlk->rx_ring)) + mask |= POLLIN | POLLRDNORM; + } + spin_unlock_bh(&sk->sk_receive_queue.lock); } - spin_unlock_bh(&sk->sk_receive_queue.lock); spin_lock_bh(&sk->sk_write_queue.lock); if (nlk->tx_ring.pg_vec) { |