Re: [RFC PATCH] iommu/vt-d: avoid panic in __dmar_remove_one_dev_info

[Jerry Snitselaar]

On Tue, Dec 17, 2019 at 10:56 AM Jerry Snitselaar <jsnitsel@xxxxxxxxxx> wrote:
>
> In addition to checking for a null pointer, verify that
> info does not have the value DEFER_DEVICE_DOMAIN_INFO or
> DUMMY_DEVICE_DOMAIN_INFO. If info has one of those values
> __dmar_remove_one_dev_info will panic when trying to access
> a member of the device_domain_info struct.
>
>     [    1.464241] BUG: unable to handle kernel NULL pointer dereference at 000000000000004e
>     [    1.464241] PGD 0 P4D 0
>     [    1.464241] Oops: 0000 [#1] SMP PTI
>     [    1.464241] CPU: 0 PID: 1 Comm: swapper/0 Tainted: G        W        --------- -  - 4.18.0-160.el8.x86_64 #1
>     [    1.464241] Hardware name: HP ProLiant DL360 Gen9/ProLiant DL360 Gen9, BIOS P89 07/21/2019
>     [    1.464241] RIP: 0010:__dmar_remove_one_dev_info+0x27/0x250
>     [    1.464241] Code: 00 00 00 0f 1f 44 00 00 8b 05 35 ec 75 01 41 56 41 55 41 54 55 53 85 c0 0f 84 99 01 00 00 48 85 ff 0f 84 92 01 00 00 48 89 fb <4c> 8b 67 50 48 8b 6f 58 $
>     [    1.464241] RSP: 0000:ffffc900000dfd10 EFLAGS: 00010082
>     [    1.464241] RAX: 0000000000000001 RBX: fffffffffffffffe RCX: 0000000000000000
>     [    1.464241] RDX: 0000000000000001 RSI: 0000000000000004 RDI: fffffffffffffffe
>     [    1.464241] RBP: ffff88ec7a72f368 R08: 0000000000000457 R09: 0000000000000039
>     [    1.464241] R10: 0000000000000000 R11: ffffc900000dfa58 R12: ffff88ec7a0eec20
>     [    1.464241] R13: ffff88ec6fd0eab0 R14: ffffffff81eae980 R15: 0000000000000000
>     [    1.464241] FS:  0000000000000000(0000) GS:ffff88ec7a600000(0000) knlGS:0000000000000000
>     [    1.464241] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>     [    1.464241] CR2: 000000000000004e CR3: 0000006c7900a001 C 00000000001606b0
>     [    1.464241] Call Trace:
>     [    1.464241]  dmar_remove_one_dev_info.isra.68+0x27/0x40
>     [    1.464241]  intel_iommu_add_device+0x124/0x180
>     [    1.464241]  ? iommu_probe_device+0x40/0x40
>     [    1.464241]  add_iommu_group+0xa/0x20
>     [    1.464241]  bus_for_each_dev+0x77/0xc0
>     [    1.464241]  ? down_write+0xe/0x40
>     [    1.464241]  bus_set_iommu+0x85/0xc0
>     [    1.464241]  intel_iommu_init+0x4b4/0x777
>     [    1.464241]  ? e820__memblock_setup+0x63/0x63
>     [    1.464241]  ? do_early_param+0x91/0x91
>     [    1.464241]  pci_iommu_init+0x19/0x45
>     [    1.464241]  do_one_initcall+0x46/0x1c3
>     [    1.464241]  ? do_early_param+0x91/0x91
>     [    1.464241]  kernel_init_freeable+0x1af/0x258
>     [    1.464241]  ? rest_init+0xaa/0xaa
>     [    1.464241]  kernel_init+0xa/0x107
>     [    1.464241]  ret_from_fork+0x35/0x40
>     [    1.464241] Modules linked in:
>     [    1.464241] CR2: 000000000000004e
>     [    1.464241] ---[ end trace 0927d2ba8b8032b5 ]---
>
> Cc: Joerg Roedel <jroedel@xxxxxxx>
> Cc: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> Cc: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx # v5.3+
> Cc: iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx
> Fixes: ae23bfb68f28 ("iommu/vt-d: Detach domain before using a private one")
> Signed-off-by: Jerry Snitselaar <jsnitsel@xxxxxxxxxx>
> ---
>  drivers/iommu/intel-iommu.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index 0c8d81f56a30..e42a09794fa2 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -5163,7 +5163,8 @@ static void dmar_remove_one_dev_info(struct device *dev)
>
>         spin_lock_irqsave(&device_domain_lock, flags);
>         info = dev->archdata.iommu;
> -       if (info)
> +       if (info && info != DEFER_DEVICE_DOMAIN_INFO
> +           && info != DUMMY_DEVICE_DOMAIN_INFO)
>                 __dmar_remove_one_dev_info(info);
>         spin_unlock_irqrestore(&device_domain_lock, flags);
>  }
> --
> 2.24.0
>
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>

I'm not positive that the DUMMY_DEVICE_DOMAIN_INFO check is needed.
It seemed like there were checks for that most places before
dmar_remove_one_dev_info
would be called, but I wasn't certain.