getifaddrs: Don't return ifa entries with NULL names [BZ #21812]

A lookup operation in map_newlink could turn into an insert because of
holes in the interface part of the map.  This leads to incorrectly set
the name of the interface to NULL when the interface is not present
for the address being processed (most likely because the interface was
added between the RTM_GETLINK and RTM_GETADDR calls to the kernel).
When such changes are detected by the kernel, it'll mark the dump as
"inconsistent" by setting NLM_F_DUMP_INTR flag on the next netlink
message.

This patch checks this condition and retries the whole operation.
Hopes are that next time the interface corresponding to the address
entry is present in the list and correct name is returned.

(cherry picked from commit c1f86a33ca32e26a9d6e29fc961e5ecb5e2e5eb4)

diff --git a/ChangeLog b/ChangeLog
index 0981fcaf7166c365975cb5ca2bc61e5516e90d14..c502aceddb32bc66ff470d5d0fe890d8a21a762f 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2018-06-29  Daniel Alvarez  <dalvarez@redhat.com>
+           Jakub Sitnicki  <jkbs@redhat.com>
+
+       [BZ #21812]
+       * sysdeps/unix/sysv/linux/ifaddrs.c (getifaddrs_internal): Retry
+       on NLM_F_DUMP_INTR.
+
 2018-06-28  Florian Weimer  <fweimer@redhat.com>
 
        [BZ #23349]

diff --git a/NEWS b/NEWS
index c34c6393eec550fc75f999d0f361a911a8563e83..db43d87ee019db34ad29f20491d673cd39815089 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -93,6 +93,7 @@ The following bugs are resolved with this release:
   [21265] x86-64: Use fxsave/xsave/xsavec in _dl_runtime_resolve
   [21269] i386 sigaction sa_restorer handling is wrong
   [21780] posix: Set p{read,write}v2 to return ENOTSUP
+  [21812] getifaddrs: Don't return ifa entries with NULL names
   [21871] x86-64: Use _dl_runtime_resolve_opt only with AVX512F
   [21885] getaddrinfo: Release resolver context on error in gethosts
   [21915] getaddrinfo: incorrect result handling for NSS service modules

diff --git a/sysdeps/unix/sysv/linux/ifaddrs.c b/sysdeps/unix/sysv/linux/ifaddrs.c
index 3bc99028639c71492029605e3399332ba2f53ab2..4f75401850f31e5391cb10d700558b0a97425be4 100644 (file)
--- a/sysdeps/unix/sysv/linux/ifaddrs.c
+++ b/sysdeps/unix/sysv/linux/ifaddrs.c
@@ -371,6 +371,14 @@ getifaddrs_internal (struct ifaddrs **ifap)
          if ((pid_t) nlh->nlmsg_pid != nh.pid || nlh->nlmsg_seq != nlp->seq)
            continue;
 
+         /* If the dump got interrupted, we can't rely on the results
+            so try again. */
+         if (nlh->nlmsg_flags & NLM_F_DUMP_INTR)
+           {
+             result = -EAGAIN;
+             goto exit_free;
+           }
+
          if (nlh->nlmsg_type == NLMSG_DONE)
            break;              /* ok */