Dropbear 2014.64

Matt Johnston matt at ucc.asn.au
Mon Jul 28 23:31:30 WST 2014


On Mon, Jul 28, 2014 at 03:06:14AM +0000, NiLuJe wrote:
> Yup, building master w/ ca86726 reverted does the trick on the machine where
> I'm experiencing this issue...

Could you try with
https://github.com/mkj/dropbear/commit/0e7409c7ff6fc760018fce3d5e8b72247bf782b5

(the same as  https://secure.ucc.asn.au/hg/dropbear/rev/36eacc322e00 )

I can sometimes reproduce it here and that patch seems to
solve the problem. I was assuming that all channel state
changes would occur through file descriptors, forgetting
about signal handlers when a process exits.

Thanks,
Matt

# HG changeset patch
# User Matt Johnston <matt at ucc.asn.au>
# Date 1406561029 -28800
# Node ID 36eacc322e00924e511810c519bf5a3f05898cdd
# Parent  356a25a108a3338b58f22a6c5b03336a10cd2bbd
Make sure the check_close() handler runs when a server child process exits

diff -r 356a25a108a3 -r 36eacc322e00 common-channel.c
--- a/common-channel.c	Mon Jul 28 22:59:16 2014 +0800
+++ b/common-channel.c	Mon Jul 28 23:23:49 2014 +0800
@@ -258,6 +258,12 @@
 			writechannel(channel, channel->errfd, channel->extrabuf);
 			do_check_close = 1;
 		}
+
+		if (ses.channel_signal_pending) {
+			/* SIGCHLD can change channel state for server sessions */
+			do_check_close = 1;
+			ses.channel_signal_pending = 0;
+		}
 	
 		/* handle any channel closing etc */
 		if (do_check_close) {
diff -r 356a25a108a3 -r 36eacc322e00 session.h
--- a/session.h	Mon Jul 28 22:59:16 2014 +0800
+++ b/session.h	Mon Jul 28 23:23:49 2014 +0800
@@ -187,6 +187,7 @@
 	unsigned int chansize; /* the number of Channel*s allocated for channels */
 	unsigned int chancount; /* the number of Channel*s in use */
 	const struct ChanType **chantypes; /* The valid channel types */
+	int channel_signal_pending; /* Flag set by sigchld handler */
 
 	/* TCP priority level for the main "port 22" tcp socket */
 	enum dropbear_prio socket_prio;
diff -r 356a25a108a3 -r 36eacc322e00 svr-chansession.c
--- a/svr-chansession.c	Mon Jul 28 22:59:16 2014 +0800
+++ b/svr-chansession.c	Mon Jul 28 23:23:49 2014 +0800
@@ -89,6 +89,9 @@
 
 	const int saved_errno = errno;
 
+	/* Make channel handling code look for closed channels */
+	ses.channel_signal_pending = 1;
+
 	TRACE(("enter sigchld handler"))
 	while ((pid = waitpid(-1, &status, WNOHANG)) > 0) {
 		TRACE(("sigchld handler: pid %d", pid))



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