Patchwork AHCI: fix Null pointer dereference in achi_host_active()

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Submitter Xiaotian Feng
Date July 17, 2013, 6:10 a.m.
Message ID <1374041439-34122-1-git-send-email-xtfeng@gmail.com>
Download mbox | patch
Permalink /patch/259599/
State Not Applicable
Delegated to: David Miller
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Comments

Xiaotian Feng - July 17, 2013, 6:10 a.m.
commit b29900e6 (AHCI: Make distinct names for ports in /proc/interrupts)
introuded a regression, which resulted Null pointer dereference for achi
host with dummy ports. For ahci ports, when the port is dummy port, its
private_data will be NULL, as ata_dummy_port_ops doesn't support ->port_start.

Reported-and-tested-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Xiaotian Feng <xtfeng@gmail.com>
Cc: Alexander Gordeev <agordeev@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: linux-ide@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
 drivers/ata/ahci.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)
Tejun Heo - July 22, 2013, 9:28 p.m.
Hello, Xiaotian.

Thanks for the fix.  A couple comments below.

On Wed, Jul 17, 2013 at 02:10:39PM +0800, Xiaotian Feng wrote:
>  	for (i = 0; i < host->n_ports; i++) {
>  		struct ahci_port_priv *pp = host->ports[i]->private_data;
> +		const char *desc;
>  
> +		if (ata_port_is_dummy(host->ports[i]))
> +			desc = dev_driver_string(host->dev);
> +		else
> +			desc = pp->irq_desc;

I think it'd be better to branch on pp.  ie. do "if (pp) desc =
pp->... " instead and then add a comment saying "pp is NULL for
dummies".

Thanks!
Xiaotian Feng - July 22, 2013, 9:31 p.m.
On Tue, Jul 23, 2013 at 5:28 AM, Tejun Heo <tj@kernel.org> wrote:
> Hello, Xiaotian.
>
> Thanks for the fix.  A couple comments below.
>
> On Wed, Jul 17, 2013 at 02:10:39PM +0800, Xiaotian Feng wrote:
>>       for (i = 0; i < host->n_ports; i++) {
>>               struct ahci_port_priv *pp = host->ports[i]->private_data;
>> +             const char *desc;
>>
>> +             if (ata_port_is_dummy(host->ports[i]))
>> +                     desc = dev_driver_string(host->dev);
>> +             else
>> +                     desc = pp->irq_desc;
>
> I think it'd be better to branch on pp.  ie. do "if (pp) desc =
> pp->... " instead and then add a comment saying "pp is NULL for
> dummies".
>

Okay, I'll update v2 patch, thanks :)

> Thanks!
>
> --
> tejun
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Patch

diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
index 5064f3e..f1de689 100644
--- a/drivers/ata/ahci.c
+++ b/drivers/ata/ahci.c
@@ -1147,10 +1147,16 @@  int ahci_host_activate(struct ata_host *host, int irq, unsigned int n_msis)
 
 	for (i = 0; i < host->n_ports; i++) {
 		struct ahci_port_priv *pp = host->ports[i]->private_data;
+		const char *desc;
 
+		if (ata_port_is_dummy(host->ports[i]))
+			desc = dev_driver_string(host->dev);
+		else
+			desc = pp->irq_desc;
+ 
 		rc = devm_request_threaded_irq(host->dev,
 			irq + i, ahci_hw_interrupt, ahci_thread_fn, IRQF_SHARED,
-			pp->irq_desc, host->ports[i]);
+			desc, host->ports[i]);
 		if (rc)
 			goto out_free_irqs;
 	}