Re: [PATCH] PCI/MSI: fix page fault when msi_populate_sysfs() failed

[Bjorn Helgaas <helgaas@kernel.org>]

For v2, please note "git log --oneline drivers/pci/msi.c" and make
your patch follow the style, including capitalization.

On Mon, Oct 11, 2021 at 05:15:28PM +0800, wanghai (M) wrote:
> 
> 在 2021/10/11 16:52, Barry Song 写道:
> > On Mon, Oct 11, 2021 at 9:24 PM Wang Hai <wanghai38@huawei.com> wrote:
> > > I got a page fault report when doing fault injection test:

When you send v2, can you include information about how you injected
the fault?  If it's easy, others can reproduce the failure that way.

> > > BUG: unable to handle page fault for address: fffffffffffffff4
> > > ...
> > > RIP: 0010:sysfs_remove_groups+0x25/0x60
> > > ...
> > > Call Trace:
> > >   msi_destroy_sysfs+0x30/0xa0
> > >   free_msi_irqs+0x11d/0x1b0
> > >   __pci_enable_msix_range+0x67f/0x760
> > >   pci_alloc_irq_vectors_affinity+0xe7/0x170
> > >   vp_find_vqs_msix+0x129/0x560
> > >   vp_find_vqs+0x52/0x230
> > >   vp_modern_find_vqs+0x47/0xb0
> > >   p9_virtio_probe+0xa1/0x460 [9pnet_virtio]
> > >   virtio_dev_probe+0x1ed/0x2e0
> > >   really_probe+0x1c7/0x400
> > >   __driver_probe_device+0xa4/0x120
> > >   driver_probe_device+0x32/0xe0
> > >   __driver_attach+0xbf/0x130
> > >   bus_for_each_dev+0xbb/0x110
> > >   driver_attach+0x27/0x30
> > >   bus_add_driver+0x1d9/0x270
> > >   driver_register+0xa9/0x180
> > >   register_virtio_driver+0x31/0x50
> > >   p9_virtio_init+0x3c/0x1000 [9pnet_virtio]
> > >   do_one_initcall+0x7b/0x380
> > >   do_init_module+0x5f/0x21e
> > >   load_module+0x265c/0x2c60
> > >   __do_sys_finit_module+0xb0/0xf0
> > >   __x64_sys_finit_module+0x1a/0x20
> > >   do_syscall_64+0x34/0xb0
> > >   entry_SYSCALL_64_after_hwframe+0x44/0xae
> > > 
> > > When populating msi_irqs sysfs failed in msi_capability_init() or
> > > msix_capability_init(), dev->msi_irq_groups will point to ERR_PTR(...).
> > > This will cause a page fault when destroying the wrong
> > > dev->msi_irq_groups in free_msi_irqs().
> > > 
> > > Fix this by setting dev->msi_irq_groups to NULL when msi_populate_sysfs()
> > > failed.
> > > 
> > > Fixes: 2f170814bdd2 ("genirq/msi: Move MSI sysfs handling from PCI to MSI core")
> > > Reported-by: Hulk Robot <hulkci@huawei.com>

What exactly was reported by the Hulk Robot?  Did it really do the
fault injection and report the page fault?

> > > Signed-off-by: Wang Hai <wanghai38@huawei.com>
> > Acked-by: Barry Song <song.bao.hua@hisilicon.com>
> > 
> > > ---
> > >   drivers/pci/msi.c | 2 ++
> > >   1 file changed, 2 insertions(+)
> > > 
> > > diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> > > index 0099a00af361..6f75db9f3be7 100644
> > > --- a/drivers/pci/msi.c
> > > +++ b/drivers/pci/msi.c
> > > @@ -561,6 +561,7 @@ static int msi_capability_init(struct pci_dev *dev, int nvec,
> > >          dev->msi_irq_groups = msi_populate_sysfs(&dev->dev);
> > >          if (IS_ERR(dev->msi_irq_groups)) {
> > >                  ret = PTR_ERR(dev->msi_irq_groups);
> > > +               dev->msi_irq_groups = NULL;
> > >                  goto err;
> > >          }
> > > 
> > > @@ -733,6 +734,7 @@ static int msix_capability_init(struct pci_dev *dev, struct msix_entry *entries,
> > >          dev->msi_irq_groups = msi_populate_sysfs(&dev->dev);
> > >          if (IS_ERR(dev->msi_irq_groups)) {
> > >                  ret = PTR_ERR(dev->msi_irq_groups);
> > > +               dev->msi_irq_groups = NULL;
> > Can you define a temp variable and assign it to dev->msi_irq_groups if
> > the temp variable
> > is not PTR_ERR?
> Of course, I will send a v2 patch.
> > 
> > >                  goto out_free;
> > >          }
> > > 
> > > --
> > > 2.17.1
> > > 
> > Thanks
> > Barry
> > .
> > 
> -- 
> Wang Hai
>