linux-kernel - [PATCH] ide-tape: Avoid potential null pointer dereference in idetape_abort

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Message-ID: <alpine.LNX.1.00.0803150123450.29784@dragon.funnycrock.com>
Date:	Sat, 15 Mar 2008 01:26:44 +0100 (CET)
From:	Jesper Juhl <jesper.juhl@...il.com>
To:	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
cc:	Gadi Oxman <gadio@...vision.net.il>,
	LKML <linux-kernel@...r.kernel.org>,
	Jesper Juhl <jesper.juhl@...il.com>
Subject: [PATCH] ide-tape: Avoid potential null pointer dereference in
 idetape_abort_pipeline()


If a NULL 'new_last_stage' is passed to idetape_abort_pipeline() then 
we'll dereference a NULL pointer and go *boom*. 
The function does test for a null pointer, unfortunately it only does it 
after having already dereferenced it.


Signed-off-by: Jesper Juhl <jesper.juhl@...il.com>
---

 ide-tape.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/ide/ide-tape.c b/drivers/ide/ide-tape.c
index 43e0e05..943290c 100644
--- a/drivers/ide/ide-tape.c
+++ b/drivers/ide/ide-tape.c
@@ -814,11 +814,14 @@ static void idetape_abort_pipeline(ide_drive_t *drive,
 				   idetape_stage_t *new_last_stage)
 {
 	idetape_tape_t *tape = drive->driver_data;
-	idetape_stage_t *stage = new_last_stage->next;
+	idetape_stage_t *stage = NULL;
 	idetape_stage_t *nstage;
 
 	debug_log(DBG_PROCS, "%s: Enter %s\n", tape->name, __func__);
 
+	if (new_last_stage)
+		stage = new_last_stage->next;
+
 	while (stage) {
 		nstage = stage->next;
 		idetape_kfree_stage(tape, stage);


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