nscd: Fix netlink cache invalidation if epoll is used [BZ #29415]

Processes cache network interface information such as whether IPv4 or IPv6
are enabled. This is only checked again if the "netlink timestamp" provided
by nscd changed, which is triggered by netlink socket activity.

However, in the epoll handler for the netlink socket, it was missed to
assign the new timestamp to the nscd database. The handler for plain poll
did that properly, copy that over.

This bug caused that e.g. processes which started before network
configuration got unusuable addresses from getaddrinfo, like IPv6 only even
though only IPv4 is available:
https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/issues/1041

It's a bit hard to reproduce, so I verified this by checking the timestamp
on calls to __check_pf manually. Without this patch it's stuck at 1, now
it's increasing on network changes as expected.

Signed-off-by: Fabian Vogt <fvogt@suse.de>
(cherry picked from commit 02ca25fef2785974011e9c5beecc99b900b69fd7)

diff --git a/NEWS b/NEWS
index 10a7613f099296e7accbeebbbb0a84dd11a23269..9360596fcc0a991108d36d85c87baac9bad4c673 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -17,6 +17,7 @@ Security related changes:
 The following bugs are resolved with this release:
 
   [28846] CMSG_NXTHDR may trigger -Wstrict-overflow warning
+  [29415] nscd: Fix netlink cache invalidation if epoll is used
   [29446] _dlopen now ignores dl_caller argument in static mode
   [29485] Linux: Terminate subprocess on late failure in tst-pidfd
   [29490] alpha: New __brk_call implementation is broken

diff --git a/nscd/connections.c b/nscd/connections.c
index 61d1674eb49a2eb48e3534662e675ff5b1936f6a..531d2e83df4fa417ff26a3cf14144f30895927f2 100644 (file)
--- a/nscd/connections.c
+++ b/nscd/connections.c
@@ -2284,7 +2284,8 @@ main_loop_epoll (int efd)
                                             sizeof (buf))) != -1)
              ;
 
-           __bump_nl_timestamp ();
+           dbs[hstdb].head->extra_data[NSCD_HST_IDX_CONF_TIMESTAMP]
+             = __bump_nl_timestamp ();
          }
 # endif
        else