Re: [PATCH] Add UNIX_DIAG_UID to Netlink UNIX socket diagnostics.

On May 17, 2019, at 12:59 AM, Andy Lutomirski [off-list ref] wrote:

quoted

On May 16, 2019, at 8:25 PM, Felipe [off-list ref] wrote:

Author: Felipe Gasper [off-list ref]
Date:   Thu May 16 12:16:53 2019 -0500

  Add UNIX_DIAG_UID to Netlink UNIX socket diagnostics.

  This adds the ability for Netlink to report a socket’s UID along with the
  other UNIX socket diagnostic information that is already available. This will
  allow diagnostic tools greater insight into which users control which socket.

  Signed-off-by: Felipe Gasper [off-list ref]

diff --git a/include/uapi/linux/unix_diag.h b/include/uapi/linux/unix_diag.h
index 5c502fd..a198857 100644
--- a/include/uapi/linux/unix_diag.h
+++ b/include/uapi/linux/unix_diag.h

@@ -20,6 +20,7 @@ struct unix_diag_req {

#define UDIAG_SHOW_ICONS    0x00000008    /* show pending connections */
#define UDIAG_SHOW_RQLEN    0x00000010    /* show skb receive queue len */
#define UDIAG_SHOW_MEMINFO    0x00000020    /* show memory info of a socket */
+#define UDIAG_SHOW_UID        0x00000040    /* show socket's UID */

struct unix_diag_msg {
  __u8    udiag_family;

@@ -40,6 +41,7 @@ enum {
  UNIX_DIAG_RQLEN,
  UNIX_DIAG_MEMINFO,
  UNIX_DIAG_SHUTDOWN,
+    UNIX_DIAG_UID,

  __UNIX_DIAG_MAX,

};

diff --git a/net/unix/diag.c b/net/unix/diag.c
index 3183d9b..011f56c 100644
--- a/net/unix/diag.c
+++ b/net/unix/diag.c

@@ -110,6 +110,11 @@ static int sk_diag_show_rqlen(struct sock *sk, struct sk_buff *nlskb)
  return nla_put(nlskb, UNIX_DIAG_RQLEN, sizeof(rql), &rql);

}

+static int sk_diag_dump_uid(struct sock *sk, struct sk_buff *nlskb)
+{
+    return nla_put(nlskb, UNIX_DIAG_UID, sizeof(kuid_t), &(sk->sk_uid));

That type is called *k* uid_t because it’s internal to the kernel. You
probably want from_kuid_munged(), which will fix it up for an
appropriate userns.  Presumably you want sk’s netns’s userns.

Thank you for pointing this out.

Would it suffice to get the userns as: “sk_user_ns(sk)”?

Or would it be better to pass struct netlink_callback *cb from unix_diag_dump() to sk_diag_dump() to sk_diag_fill(), then to the new function to add the UID?

cheers,
-Felipe Gasper