On Sun, 2015-09-20 at 05:18 -0400, Aaron Conole wrote:
> From: Aaron Conole <aa...@bytheb.org>
>
> AF_UNIX sockets now return multiple skbs from recv() when MSG_PEEK flag
> is set.
>
> This is referenced in kernel bugzilla #12323 @
> https://bugzilla.kernel.org/show_bug.cgi?id=12323
>
> As described both in the BZ and lkml thread @
> http://lkml.org/lkml/2008/1/8/444 calling recv() with MSG_PEEK on an
> AF_UNIX socket only reads a single skb, where the desired effect is
> to return as much skb data has been queued, until hitting the recv
> buffer size (whichever comes first).
>
> The modified MSG_PEEK path will now move to the next skb in the tree
> and jump to the again: label, rather than following the natural loop
> structure. This requires duplicating some of the loop head actions.
>
> This was tested using the python socketpair python code attached to
> the bugzilla issue.
>
> Signed-off-by: Aaron Conole <aa...@bytheb.org>
> ---
> net/unix/af_unix.c | 19 +++++++++++++++++--
> 1 file changed, 17 insertions(+), 2 deletions(-)
>
> diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
> index 03ee4d3..988fbbd4 100644
> --- a/net/unix/af_unix.c
> +++ b/net/unix/af_unix.c
> @@ -2179,9 +2179,24 @@ unlock:
> if (UNIXCB(skb).fp)
> scm.fp = scm_fp_dup(UNIXCB(skb).fp);
>
> - sk_peek_offset_fwd(sk, chunk);
> + if (skip) {
> + sk_peek_offset_fwd(sk, chunk);
> + skip -= chunk;
> + }
>
> - break;
> + if (UNIXCB(skb).fp)
> + break;
> +
> + /* XXX - this is ugly; a better approach would be
> + * rewriting this function
> + */
> + last = skb;
> + last_len = skb->len;
> + unix_state_lock(&sk);
I am wondering what this is expected to do, and how this code would
possibly not trigger a crash.
Are you 100% sure you tested this patch and code path ?
Before resending v3, please make sure to compile and test with
CONFIG_LOCKDEP=y. Add a temporary (in your tree, not final patch)
pr_err_once("went there at least one time\n");
(to make sure this code path was tested)
It might be time to get rid of unix_sk macro for a proper function to
avoid these kind of errors.
diff --git a/include/net/af_unix.h b/include/net/af_unix.h
index 4a167b30a12f..cb1b9bbda332 100644
--- a/include/net/af_unix.h
+++ b/include/net/af_unix.h
@@ -63,7 +63,11 @@ struct unix_sock {
#define UNIX_GC_MAYBE_CYCLE 1
struct socket_wq peer_wq;
};
-#define unix_sk(__sk) ((struct unix_sock *)__sk)
+
+static inline struct unix_sock *unix_sk(struct sock *sk)
+{
+ return (struct unix_sock *)sk;
+}
#define peer_wait peer_wq.wait
Thanks.
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