forked from jengelh/iptables
83 lines
2.7 KiB
Diff
83 lines
2.7 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-1.8.11/iptables/iptables-batch.c
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===================================================================
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--- iptables-1.8.11.orig/iptables/iptables-batch.c
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+++ iptables-1.8.11/iptables/iptables-batch.c
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@@ -44,6 +44,7 @@
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#include <iptables.h>
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#endif
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#include <xtables.h>
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+#include "xshared.h"
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#ifdef IP6T
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#define prog_name ip6tables_globals.program_name
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@@ -403,6 +404,26 @@ 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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+ if (!xtables_lock_or_exit(-1)) {
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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-1.8.11/iptables/xshared.c
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===================================================================
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--- iptables-1.8.11.orig/iptables/xshared.c
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+++ iptables-1.8.11/iptables/xshared.c
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@@ -255,10 +255,14 @@ 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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@@ -278,8 +282,10 @@ 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 | (wait ? 0 : LOCK_NB)) == 0)
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+ if (flock(fd, LOCK_EX | (wait ? 0 : LOCK_NB)) == 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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