linux-hardening - Re: [PATCH RFC] scsi: qla2xxx: zero default_item last in qla24xx_free_purex

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Message-ID: <CAHhmqcTdC_we4x9e0Q-NT=k-9LM5Q8azFH51_Wbpr4tKgpOzDg@mail.gmail.com>
Date: Thu, 25 Sep 2025 14:43:04 -0400
From: Bryan Gurney <bgurney@...hat.com>
To: "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc: jmeneghi@...hat.com, linux-nvme@...ts.infradead.org, kbusch@...nel.org, 
	hch@....de, sagi@...mberg.me, axboe@...nel.dk, james.smart@...adcom.com, 
	njavali@...vell.com, linux-scsi@...r.kernel.org, hare@...e.de, 
	linux-hardening@...r.kernel.org, kees@...nel.org, gustavoars@...nel.org, 
	emilne@...hat.com
Subject: Re: [PATCH RFC] scsi: qla2xxx: zero default_item last in qla24xx_free_purex_item

On Thu, Sep 25, 2025 at 1:23 PM Gustavo A. R. Silva
<gustavo@...eddedor.com> wrote:
>
>
>
> On 9/25/25 19:02, Bryan Gurney wrote:
> > In order to avoid a null pointer dereference, the vha->default_item
> > should be set to 0 last if the item pointer passed to the function
> > matches.
> >
> > BUG: kernel NULL pointer dereference, address: 0000000000000936
> > ...
> > RIP: 0010:qla24xx_free_purex_item+0x5e/0x90 [qla2xxx]
> > ...
> > Call Trace:
> >   <TASK>
> >   qla24xx_process_purex_list+0xda/0x110 [qla2xxx]
> >   qla2x00_do_dpc+0x8ac/0xab0 [qla2xxx]
> >   ? __pfx_qla2x00_do_dpc+0x10/0x10 [qla2xxx]
> >   kthread+0xf9/0x240
> >   ? __pfx_kthread+0x10/0x10
> >   ret_from_fork+0xf1/0x110
> >   ? __pfx_kthread+0x10/0x10
> >
> > Also use a local variable to avoid multiple de-referencing of the item.
> >
> > Fixes: 6f4b10226b6b ("scsi: qla2xxx: Fix memcpy() field-spanning write issue")
> > Signed-off-by: Bryan Gurney <bgurney@...hat.com>
> > ---
> >   drivers/scsi/qla2xxx/qla_os.c | 8 +++++---
> >   1 file changed, 5 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/scsi/qla2xxx/qla_os.c b/drivers/scsi/qla2xxx/qla_os.c
> > index 98a5c105fdfd..7e28c7e9aa60 100644
> > --- a/drivers/scsi/qla2xxx/qla_os.c
> > +++ b/drivers/scsi/qla2xxx/qla_os.c
> > @@ -6459,9 +6459,11 @@ void qla24xx_process_purex_rdp(struct scsi_qla_host *vha,
> >   void
> >   qla24xx_free_purex_item(struct purex_item *item)
> >   {
> > -     if (item == &item->vha->default_item) {
> > -             memset(&item->vha->default_item, 0, sizeof(struct purex_item));
> > -             memset(&item->vha->__default_item_iocb, 0, QLA_DEFAULT_PAYLOAD_SIZE);
> > +     scsi_qla_host_t *base_vha = item->vha;
> > +
> > +     if (item == &base_vha->default_item) {
> > +             memset(&base_vha->__default_item_iocb, 0, QLA_DEFAULT_PAYLOAD_SIZE);
> > +             memset(&base_vha->default_item, 0, sizeof(struct purex_item));
> >       } else
> >               kfree(item);
> >   }
>
> I see. I think it's probably better to go ahead with the revert, and then apply
> the patch I proposed in my previous e-mail (it's more straightforward and introduces
> fewer changes).
>
> If you agree with that, I can submit both the revert and the patch.
>
> Thanks
> -Gustavo
>

Hi Gustavo,

I just built a kernel with your patch, on top of the NVMe FPIN link
integrity v9 patch set, and a test run on qla2xxx passes without any
field-spanning write warnings, nor with any null pointer dereference
errors.


Thanks,

Bryan