linux-kernel - Re: [PATCH] vfio/spapr: fail tce_iommu_attach_group() when iommu

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Message-ID: <20170131033550.GM14879@umbus.fritz.box>
Date:   Tue, 31 Jan 2017 14:35:50 +1100
From:   David Gibson <david@...son.dropbear.id.au>
To:     Alex Williamson <alex.williamson@...hat.com>
Cc:     Greg Kurz <groug@...d.org>, kvm@...r.kernel.org,
        Alexey Kardashevskiy <aik@...abs.ru>,
        linux-kernel@...r.kernel.org,
        Vaibhav Jain <vaibhav@...ux.vnet.ibm.com>
Subject: Re: [PATCH] vfio/spapr: fail tce_iommu_attach_group() when
 iommu_data is null

On Tue, Jan 24, 2017 at 11:07:59AM -0700, Alex Williamson wrote:
> On Tue, 24 Jan 2017 17:50:26 +0100
> Greg Kurz <groug@...d.org> wrote:
> 
> > The recently added mediated VFIO driver doesn't know about powerpc iommu.
> > It thus doesn't register a struct iommu_table_group in the iommu group
> > upon device creation. The iommu_data pointer hence remains null.
> > 
> > This causes a kernel oops when userspace tries to set the iommu type of a
> > container associated with a mediated device to VFIO_SPAPR_TCE_v2_IOMMU.
> > 
> > [   82.585440] mtty mtty: MDEV: Registered
> > [   87.655522] iommu: Adding device 83b8f4f2-509f-382f-3c1e-e6bfe0fa1001 to group 10
> > [   87.655527] vfio_mdev 83b8f4f2-509f-382f-3c1e-e6bfe0fa1001: MDEV: group_id = 10
> > [  116.297184] Unable to handle kernel paging request for data at address 0x00000030
> > [  116.297389] Faulting instruction address: 0xd000000007870524
> > [  116.297465] Oops: Kernel access of bad area, sig: 11 [#1]
> > [  116.297611] SMP NR_CPUS=2048
> > [  116.297611] NUMA
> > [  116.297627] PowerNV
> > ...
> > [  116.297954] CPU: 33 PID: 7067 Comm: qemu-system-ppc Not tainted 4.10.0-rc5-mdev-test #8
> > [  116.297993] task: c000000e7718b680 task.stack: c000000e77214000
> > [  116.298025] NIP: d000000007870524 LR: d000000007870518 CTR: 0000000000000000
> > [  116.298064] REGS: c000000e77217990 TRAP: 0300   Not tainted  (4.10.0-rc5-mdev-test)
> > [  116.298103] MSR: 9000000000009033 <SF,HV,EE,ME,IR,DR,RI,LE>
> > [  116.298107]   CR: 84004444  XER: 00000000
> > [  116.298154] CFAR: c00000000000888c DAR: 0000000000000030 DSISR: 40000000 SOFTE: 1
> >                GPR00: d000000007870518 c000000e77217c10 d00000000787b0ed c000000eed2103c0
> >                GPR04: 0000000000000000 0000000000000000 c000000eed2103e0 0000000f24320000
> >                GPR08: 0000000000000104 0000000000000001 0000000000000000 d0000000078729b0
> >                GPR12: c00000000025b7e0 c00000000fe08400 0000000000000001 000001002d31d100
> >                GPR16: 000001002c22c850 00003ffff315c750 0000000043145680 0000000043141bc0
> >                GPR20: ffffffffffffffed fffffffffffff000 0000000020003b65 d000000007706018
> >                GPR24: c000000f16cf0d98 d000000007706000 c000000003f42980 c000000003f42980
> >                GPR28: c000000f1575ac00 c000000003f429c8 0000000000000000 c000000eed2103c0
> > [  116.298504] NIP [d000000007870524] tce_iommu_attach_group+0x10c/0x360 [vfio_iommu_spapr_tce]
> > [  116.298555] LR [d000000007870518] tce_iommu_attach_group+0x100/0x360 [vfio_iommu_spapr_tce]
> > [  116.298601] Call Trace:
> > [  116.298610] [c000000e77217c10] [d000000007870518] tce_iommu_attach_group+0x100/0x360 [vfio_iommu_spapr_tce] (unreliable)
> > [  116.298671] [c000000e77217cb0] [d0000000077033a0] vfio_fops_unl_ioctl+0x278/0x3e0 [vfio]
> > [  116.298713] [c000000e77217d40] [c0000000002a3ebc] do_vfs_ioctl+0xcc/0x8b0
> > [  116.298745] [c000000e77217de0] [c0000000002a4700] SyS_ioctl+0x60/0xc0
> > [  116.298782] [c000000e77217e30] [c00000000000b220] system_call+0x38/0xfc
> > [  116.298812] Instruction dump:
> > [  116.298828] 7d3f4b78 409effc8 3d220000 e9298020 3c800140 38a00018 608480c0 e8690028
> > [  116.298869] 4800249d e8410018 7c7f1b79 41820230 <e93e0030> 2fa90000 419e0114 e9090020
> > [  116.298914] ---[ end trace 1e10b0ced08b9120 ]---
> > 
> > This patch fixes the oops.
> > 
> > Reported-by: Vaibhav Jain <vaibhav@...ux.vnet.ibm.com>
> > Signed-off-by: Greg Kurz <groug@...d.org>
> > ---
> >  drivers/vfio/vfio_iommu_spapr_tce.c |    4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
> > index c8823578a1b2..128d10282d16 100644
> > --- a/drivers/vfio/vfio_iommu_spapr_tce.c
> > +++ b/drivers/vfio/vfio_iommu_spapr_tce.c
> > @@ -1270,6 +1270,10 @@ static int tce_iommu_attach_group(void *iommu_data,
> >  	/* pr_debug("tce_vfio: Attaching group #%u to iommu %p\n",
> >  			iommu_group_id(iommu_group), iommu_group); */
> >  	table_group = iommu_group_get_iommudata(iommu_group);
> > +	if (!table_group) {
> > +		ret = -ENODEV;
> > +		goto unlock_exit;
> > +	}
> >  
> >  	if (tce_groups_attached(container) && (!table_group->ops ||
> >  			!table_group->ops->take_ownership ||
> > 
> 
> Seems sane to me.
> 
> David/Alexey, please review.  Thanks,

Seems reasonable.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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