Re: [PATCH v4] svc-i3c-master: Fix read from unreadable memory at svc_i3c_master_ibi_work()

[Alexandre Belloni <alexandre.belloni@bootlin.com>]

On 17/03/2025 15:46:52+0000, Manjunatha Venkatesh wrote:
> 
> 
> > -----Original Message-----
> > From: Frank Li <frank.li@nxp.com>
> > Sent: Monday, March 17, 2025 6:57 PM
> > To: Manjunatha Venkatesh <manjunatha.venkatesh@nxp.com>
> > Cc: miquel.raynal@bootlin.com; conor.culhane@silvaco.com;
> > alexandre.belloni@bootlin.com; linux-i3c@lists.infradead.org; linux-
> > kernel@vger.kernel.org; stable@vger.kernel.org; rvmanjumce@gmail.com
> > Subject: Re: [PATCH v4] svc-i3c-master: Fix read from unreadable memory at
> > svc_i3c_master_ibi_work()
> > 
> > On Thu, Mar 13, 2025 at 05:15:42AM +0000, Manjunatha Venkatesh wrote:
> > >
> > >
> > > > -----Original Message-----
> > > > From: Frank Li <frank.li@nxp.com>
> > > > Sent: Wednesday, March 12, 2025 11:59 PM
> > > > To: Manjunatha Venkatesh <manjunatha.venkatesh@nxp.com>
> > > > Cc: miquel.raynal@bootlin.com; conor.culhane@silvaco.com;
> > > > alexandre.belloni@bootlin.com; linux-i3c@lists.infradead.org; linux-
> > > > kernel@vger.kernel.org; stable@vger.kernel.org; rvmanjumce@gmail.com
> > > > Subject: Re: [PATCH v4] svc-i3c-master: Fix read from unreadable
> > > > memory at
> > > > svc_i3c_master_ibi_work()
> > > >
> > > > On Wed, Mar 12, 2025 at 07:23:56PM +0530, Manjunatha Venkatesh
> > wrote:
> > > > > As part of I3C driver probing sequence for particular device
> > > > > instance, While adding to queue it is trying to access ibi
> > > > > variable of dev which is not yet initialized causing "Unable to
> > > > > handle kernel read from unreadable memory" resulting in kernel panic.
> > > > >
> > > > > Below is the sequence where this issue happened.
> > > > > 1. During boot up sequence IBI is received at host  from the slave device
> > > > >    before requesting for IBI, Usually will request IBI by calling
> > > > >    i3c_device_request_ibi() during probe of slave driver.
> > > > > 2. Since master code trying to access IBI Variable for the particular
> > > > >    device instance before actually it initialized by slave driver,
> > > > >    due to this randomly accessing the address and causing kernel panic.
> > > > > 3. i3c_device_request_ibi() function invoked by the slave driver where
> > > > >    dev->ibi = ibi; assigned as part of function call
> > > > >    i3c_dev_request_ibi_locked().
> > > > > 4. But when IBI request sent by slave device, master code  trying to
> > access
> > > > >    this variable before its initialized due to this race condition
> > > > >    situation kernel panic happened.
> > > > >
> > > > > Fixes: dd3c52846d595 ("i3c: master: svc: Add Silvaco I3C master
> > > > > driver")
> > > > > Cc: stable@vger.kernel.org
> > > > > Signed-off-by: Manjunatha Venkatesh
> > <manjunatha.venkatesh@nxp.com>
> > > > > ---
> > > > > Changes since v3:
> > > > >   - Description  updated typo "Fixes:"
> > > > >
> > > > >  drivers/i3c/master/svc-i3c-master.c | 7 +++++--
> > > > >  1 file changed, 5 insertions(+), 2 deletions(-)
> > > > >
> > > > > diff --git a/drivers/i3c/master/svc-i3c-master.c
> > > > > b/drivers/i3c/master/svc-i3c-master.c
> > > > > index d6057d8c7dec..98c4d2e5cd8d 100644
> > > > > --- a/drivers/i3c/master/svc-i3c-master.c
> > > > > +++ b/drivers/i3c/master/svc-i3c-master.c
> > > > > @@ -534,8 +534,11 @@ static void svc_i3c_master_ibi_work(struct
> > > > work_struct *work)
> > > > >  	switch (ibitype) {
> > > > >  	case SVC_I3C_MSTATUS_IBITYPE_IBI:
> > > > >  		if (dev) {
> > > > > -			i3c_master_queue_ibi(dev, master->ibi.tbq_slot);
> > > > > -			master->ibi.tbq_slot = NULL;
> > > > > +			data = i3c_dev_get_master_data(dev);
> > > > > +			if (master->ibi.slots[data->ibi]) {
> > > > > +				i3c_master_queue_ibi(dev, master-
> > > > >ibi.tbq_slot);
> > > > > +				master->ibi.tbq_slot = NULL;
> > > > > +			}
> > > >
> > > > You still not reply previous discussion:
> > > >
> > > > https://lore.kernel.org/linux-i3c/Z8sOKZSjHeeP2mY5@lizhi-Precision-T
> > > > ower-
> > > > 5810/T/#mfd02d6ddca0a4b57bc823dcbfa7571c564800417
> > > >
> > > [Manjunatha Venkatesh] : In the last mail answered to this question.
> > >
> > > > This is not issue only at svc driver, which should be common problem
> > > > for other master controller drivers
> > > >
> > > [Manjunatha Venkatesh] :Yes, you are right.
> > > One of my project I3C interface is required, where we have used IMX board
> > as reference platform.
> > > As part of boot sequence we come across this issue and tried to fix that
> > particular controller driver.
> > >
> > > What is your conclusion on this? Is it not ok to take patch for SVC alone?
> > 
> > I perfer fix at common framwork to avoid every driver copy the similar logic
> > code.
> > 
> [Manjunatha Venkatesh] : As per your suggestion tried the below patch at common framework api i3c_master_queue_ibi()
>  and looks working fine, didn't see any crash issue.
> if (!dev->ibi || !slot) {
>              dev_warning("...");

Do we really need a warning, what would be the user action after seeing
it?
>              return;
> }
> Will commit this change in next patch submission.
> 
> > Frank
> > 
> > >
> > > > Frank
> > > >
> > > > >  		}
> > > > >  		svc_i3c_master_emit_stop(master);
> > > > >  		break;
> > > > > --
> > > > > 2.46.1
> > > > >
> > >
> > > --
> > > linux-i3c mailing list
> > > linux-i3c@lists.infradead.org
> > > http://lists.infradead.org/mailman/listinfo/linux-i3c

-- 
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com