File 0001-Fix-NULL-pointer-dereference-for-pseudo-ch... of Package dahdi-linux

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File 0001-Fix-NULL-pointer-dereference-for-pseudo-channels.patch of Package dahdi-linux (Revision 525c13fafe767868200d4c456c6f2ff0)

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From 57dbc69bd7b9b7d98944f3b489d8fa185d5accbd Mon Sep 17 00:00:00 2001
From: Harald Welte <laforge@osmocom.org>
Date: Sat, 16 Apr 2022 13:32:57 +0200
Subject: [PATCH 1/6] Fix NULL pointer dereference for pseudo channels

pseudo channels are characterized by the fact that they have their span
member set to NULL.  This is illustrated by the is_pseudo_chan()
function.

However, when using RXMIRROR/TXMIRROR, __putbuf_chunk() is called not
just on the real channel, but also on the mirror (pseudo) channel.

Hence, __putbuf_chunk() and friends must not dereference the ->span
member without first checking that this channel actually does have
a non-NULL span assigned.

I originally thought that those unconditional de-references must have
been introduced after the RXMIRROR/TXMIRROR was merged - but checked the
git history and it seems like the bug has been present ever sicne
this functionality was merged in 2010 in commit
9090c6fcd289b497e00e8e5fb9cc3546e0dfe7d6

Change-Id: I747a696c9a5865c11461b6357a10346a8d0d1621
Closes: OS#5531
---
 drivers/dahdi/dahdi-base.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/dahdi/dahdi-base.c b/drivers/dahdi/dahdi-base.c
index 96e4afd..2b6256b 100644
--- a/drivers/dahdi/dahdi-base.c
+++ b/drivers/dahdi/dahdi-base.c
@@ -9203,7 +9203,7 @@ static void __putbuf_chunk(struct dahdi_chan *ss, unsigned char *rxb, int bytes)
 						buf[ms->readidx[ms->inreadbuf]++] = rxc;
 						/* Pay attention to the possibility of an overrun */
 						if (ms->readidx[ms->inreadbuf] >= ms->blocksize) {
-							if (!ss->span->alarms)
+							if (ss->span && !ss->span->alarms)
 								module_printk(KERN_WARNING, "HDLC Receiver overrun on channel %s (master=%s)\n", ss->name, ss->master->name);
 							abort=DAHDI_EVENT_OVERRUN;
 							/* Force the HDLC state back to frame-search mode */
@@ -9375,7 +9375,7 @@ that the waitqueue is empty. */
 					tasklet_schedule(&ms->ppp_calls);
 				} else
 #endif
-					if (test_bit(DAHDI_FLAGBIT_OPEN, &ms->flags) && !ss->span->alarms) {
+					if (test_bit(DAHDI_FLAGBIT_OPEN, &ms->flags) && ss->span && !ss->span->alarms) {
 						/* Notify the receiver... */
 						__qevent(ss->master, abort);
 					}
@@ -9443,7 +9443,7 @@ static void __dahdi_hdlc_abort(struct dahdi_chan *ss, int event)
 {
 	if (ss->inreadbuf >= 0)
 		ss->readidx[ss->inreadbuf] = 0;
-	if (test_bit(DAHDI_FLAGBIT_OPEN, &ss->flags) && !ss->span->alarms)
+	if (test_bit(DAHDI_FLAGBIT_OPEN, &ss->flags) && ss->span && !ss->span->alarms)
 		__qevent(ss->master, event);
 }
 
-- 
2.36.0

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File 0001-Fix-NULL-pointer-dereference-for-pseudo-channels.patch of Package dahdi-linux (Revision 525c13fafe767868200d4c456c6f2ff0)

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