socketutils: use exact match of unix domain sockets on fresh kernels

* socketutils.c (unix_send_query): Do not add NLM_F_DUMP to nlmsg_flags
when kernel version is 4.4.4 or later, initialize udiag_cookie
unconditionally.

Complements: v4.12~536 ("Change unix_diag requests back to use full dump instead of exact match")

diff --git a/socketutils.c b/socketutils.c
index b6b12c766cde026e9d310b15aef4a1e40bea31db..a646b5b2ce9ab0ad09bbc5ea846e47afb58c3ead 100644 (file)
--- a/socketutils.c
+++ b/socketutils.c
@@ -252,6 +252,13 @@ receive_responses(struct tcb *tcp, const int fd, const unsigned long inode,
 static bool
 unix_send_query(struct tcb *tcp, const int fd, const unsigned long inode)
 {
+       /*
+        * The kernel bug was fixed in mainline by commit v4.5-rc6~35^2~11
+        * and backported to stable/linux-4.4.y by commit v4.4.4~297.
+        */
+       const uint16_t dump_flag =
+               os_release < KERNEL_VERSION(4, 4, 4) ? NLM_F_DUMP : 0;
+
        struct {
                const struct nlmsghdr nlh;
                const struct unix_diag_req udr;
@@ -259,13 +266,14 @@ unix_send_query(struct tcb *tcp, const int fd, const unsigned long inode)
                .nlh = {
                        .nlmsg_len = sizeof(req),
                        .nlmsg_type = SOCK_DIAG_BY_FAMILY,
-                       .nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST
+                       .nlmsg_flags = NLM_F_REQUEST | dump_flag
                },
                .udr = {
                        .sdiag_family = AF_UNIX,
                        .udiag_ino = inode,
                        .udiag_states = -1,
-                       .udiag_show = UDIAG_SHOW_NAME | UDIAG_SHOW_PEER
+                       .udiag_show = UDIAG_SHOW_NAME | UDIAG_SHOW_PEER,
+                       .udiag_cookie = { ~0U, ~0U }
                }
        };
        return send_query(tcp, fd, &req, sizeof(req));