76 lines
2.5 KiB
Diff
76 lines
2.5 KiB
Diff
From: Matthias Gerstner <matthias.gerstner@suse.com>
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Date: 2017-06-26T10:53:24+0000
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- fix a locking issue of iptables-batch which can cause it to spuriously fail
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when other programs modify the iptables rules in parallel (bnc#1045130).
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This can especially affect SuSEfirewall2 during startup.
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---
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iptables/iptables-batch.c | 21 +++++++++++++++++++++
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iptables/xshared.c | 8 +++++++-
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2 files changed, 28 insertions(+), 1 deletion(-)
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Index: iptables-1.8.8/iptables/iptables-batch.c
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===================================================================
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--- iptables-1.8.8.orig/iptables/iptables-batch.c
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+++ iptables-1.8.8/iptables/iptables-batch.c
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@@ -403,6 +403,27 @@ main(int argc, char *argv[])
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tables[3].name = "raw";
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tables[3].handle = NULL;
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current_table = &tables[0];
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+ /*
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+ * We need to lock the complete batch processing against parallel
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+ * modification by other processes. Otherwise, we can end up with
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+ * EAGAIN errors.
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+ *
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+ * The do_command{4,6} function already locks itself, but the complete
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+ * call sequence needs to be locked until the commit is performed.
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+ *
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+ * Sadly, the xtables_lock() implementation is not very cooperative.
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+ * There is no unlock() equivalent. The lock file descriptor is simply
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+ * left open until the process exits. Thus, we would have deadlocks
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+ * when calling do_command{4,6} the second time.
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+ *
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+ * To prevent this, part of this patch adds logic to avoid taking the
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+ * lock a second time in the same process in xtables_lock()
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+ */
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+ const struct timeval wait_interval = {.tv_sec = 1};
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+ if (!xtables_lock_or_exit(-1, &wait_interval)) {
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+ fprintf(stderr, "failed to acquire the xtables lock\n");
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+ exit(1);
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+ }
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while((r = getline(&iline, &llen, fp)) != -1)
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{
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Index: iptables-1.8.8/iptables/xshared.c
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===================================================================
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--- iptables-1.8.8.orig/iptables/xshared.c
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+++ iptables-1.8.8/iptables/xshared.c
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@@ -262,10 +262,14 @@ static void alarm_ignore(int i) {
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static int xtables_lock(int wait)
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{
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+ static bool already_locked = false;
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struct sigaction sigact_alarm;
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const char *lock_file;
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int fd;
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+ if (already_locked)
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+ /* Avoid deadlocks, see iptables-batch.c */
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+ return true;
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lock_file = getenv("XTABLES_LOCKFILE");
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if (lock_file == NULL || lock_file[0] == '\0')
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lock_file = XT_LOCK_NAME;
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@@ -285,8 +289,10 @@ static int xtables_lock(int wait)
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alarm(wait);
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}
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- if (flock(fd, LOCK_EX) == 0)
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+ if (flock(fd, LOCK_EX) == 0) {
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+ already_locked = true;
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return fd;
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+ }
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if (errno == EINTR) {
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errno = EWOULDBLOCK;
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