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References: <20211011084049.53643-1-wanghai38@huawei.com>
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From:   Barry Song <21cnbao@gmail.com>
Date:   Mon, 11 Oct 2021 21:52:02 +1300
Message-ID: <CAGsJ_4yHW5YbmErTdv7Hq3-XOVL_-t5OdDR8WEYGyXyqiQmRxA@mail.gmail.com>
Subject: Re: [PATCH] PCI/MSI: fix page fault when msi_populate_sysfs() failed
To:     Wang Hai <wanghai38@huawei.com>
Cc:     Bjorn Helgaas <bhelgaas@google.com>, Marc Zyngier <maz@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Barry Song <song.bao.hua@hisilicon.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-pci@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>
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Precedence: bulk

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:
>
> 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>
> 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?

>                 goto out_free;
>         }
>
> --
> 2.17.1
>

Thanks
Barry