Patchwork [03/13] ide: Potential null pointer dereference in ide_queue_pc_tail()

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Submitter Marina Makienko
Date Aug. 9, 2012, 1:55 p.m.
Message ID <1344520529-19164-1-git-send-email-makienko@ispras.ru>
Download mbox | patch
Permalink /patch/176103/
State Rejected
Delegated to: David Miller
Headers show

Comments

Marina Makienko - Aug. 9, 2012, 1:55 p.m.
The function blk_get_request() can return NULL in some cases. There are
checks on it if function is called with argumetns one of which is
GFP_ATOMIC/GFP_NOIO/etc. If system couldn't find request
blk_get_request() return NULL.

But if there is function call with argument __GFP_WAIT
the system will wait until get request or the queue becomes
dead. If something kills the queue, blk_get_request()
return NULL and next operations will lead to errors.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Marina Makienko <makienko@ispras.ru>
---
 drivers/ide/ide-atapi.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)
Alan Cox - Aug. 9, 2012, 2:13 p.m.
On Thu,  9 Aug 2012 17:55:20 +0400
Marina Makienko <makienko@ispras.ru> wrote:

> The function blk_get_request() can return NULL in some cases. There are
> checks on it if function is called with argumetns one of which is
> GFP_ATOMIC/GFP_NOIO/etc. If system couldn't find request
> blk_get_request() return NULL.

drivers/ide is obsolete and scheduled for removal. I'm not sure messing
with it is remotely useful at this point ?
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David Miller - Aug. 9, 2012, 9:49 p.m.
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
Date: Thu, 9 Aug 2012 15:13:42 +0100

> On Thu,  9 Aug 2012 17:55:20 +0400
> Marina Makienko <makienko@ispras.ru> wrote:
> 
>> The function blk_get_request() can return NULL in some cases. There are
>> checks on it if function is called with argumetns one of which is
>> GFP_ATOMIC/GFP_NOIO/etc. If system couldn't find request
>> blk_get_request() return NULL.
> 
> drivers/ide is obsolete and scheduled for removal. I'm not sure messing
> with it is remotely useful at this point ?

Agreed, I'm not applying this stuff.
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Sergei Shtylyov - Aug. 17, 2012, 5 p.m.
Hello.

On 09.08.2012 18:13, Alan Cox wrote:

> On Thu,  9 Aug 2012 17:55:20 +0400
> Marina Makienko <makienko@ispras.ru> wrote:

>> The function blk_get_request() can return NULL in some cases. There are
>> checks on it if function is called with argumetns one of which is
>> GFP_ATOMIC/GFP_NOIO/etc. If system couldn't find request
>> blk_get_request() return NULL.

> drivers/ide is obsolete and scheduled for removal.

    When it was scheduled for removal? I can't find an entry in 
Documentation/feature-removal-schedule.txt. And how can that be when there 
are still many unconverted drivers?

> I'm not sure messing with it is remotely useful at this point ?

    It's being maintained for bug fixes still, AFAIK.

MBR, Sergei

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Patch

diff --git a/drivers/ide/ide-atapi.c b/drivers/ide/ide-atapi.c
index fac3d9d..8bf4109 100644
--- a/drivers/ide/ide-atapi.c
+++ b/drivers/ide/ide-atapi.c
@@ -93,6 +93,12 @@  int ide_queue_pc_tail(ide_drive_t *drive, struct gendisk *disk,
 	int error;
 
 	rq = blk_get_request(drive->queue, READ, __GFP_WAIT);
+
+	if (!rq) {
+		printk(KERN_ERR PFX"ide_queue_pc_tail: blk_get_request() failed. \n");
+		return 1;
+	}
+
 	rq->cmd_type = REQ_TYPE_SPECIAL;
 	rq->special = (char *)pc;