linux-kernel - [tip: x86/urgent] x86/dma: Tear down DMA ops on driver unbind

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Date:   Thu, 15 Apr 2021 09:00:57 -0000
From:   "tip-bot2 for Jean-Philippe Brucker" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     "Jean-Philippe Brucker" <jean-philippe@...aro.org>,
        Borislav Petkov <bp@...e.de>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: x86/urgent] x86/dma: Tear down DMA ops on driver unbind

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     9f8614f5567eb4e38579422d38a1bdfeeb648ffc
Gitweb:        https://git.kernel.org/tip/9f8614f5567eb4e38579422d38a1bdfeeb648ffc
Author:        Jean-Philippe Brucker <jean-philippe@...aro.org>
AuthorDate:    Wed, 14 Apr 2021 10:26:34 +02:00
Committer:     Borislav Petkov <bp@...e.de>
CommitterDate: Thu, 15 Apr 2021 10:27:29 +02:00

x86/dma: Tear down DMA ops on driver unbind

Since

  08a27c1c3ecf ("iommu: Add support to change default domain of an iommu group")

a user can switch a device between IOMMU and direct DMA through sysfs.
This doesn't work for AMD IOMMU at the moment because dev->dma_ops is
not cleared when switching from a DMA to an identity IOMMU domain. The
DMA layer thus attempts to use the dma-iommu ops on an identity domain,
causing an oops:

  # echo 0000:00:05.0 > /sys/sys/bus/pci/drivers/e1000e/unbind
  # echo identity > /sys/bus/pci/devices/0000:00:05.0/iommu_group/type
  # echo 0000:00:05.0 > /sys/sys/bus/pci/drivers/e1000e/bind
   ...
  BUG: kernel NULL pointer dereference, address: 0000000000000028
   ...
   Call Trace:
    iommu_dma_alloc
    e1000e_setup_tx_resources
    e1000e_open

Implement arch_teardown_dma_ops() on x86 to clear the device's dma_ops
pointer during driver unbind.

 [ bp: Massage commit message. ]

Fixes: 08a27c1c3ecf ("iommu: Add support to change default domain of an iommu group")
Signed-off-by: Jean-Philippe Brucker <jean-philippe@...aro.org>
Signed-off-by: Borislav Petkov <bp@...e.de>
Link: https://lkml.kernel.org/r/20210414082633.877461-1-jean-philippe@linaro.org
---
 arch/x86/Kconfig          | 1 +
 arch/x86/kernel/pci-dma.c | 7 +++++++
 2 files changed, 8 insertions(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 2792879..2c90f8d 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -85,6 +85,7 @@ config X86
 	select ARCH_HAS_STRICT_MODULE_RWX
 	select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
 	select ARCH_HAS_SYSCALL_WRAPPER
+	select ARCH_HAS_TEARDOWN_DMA_OPS	if IOMMU_DMA
 	select ARCH_HAS_UBSAN_SANITIZE_ALL
 	select ARCH_HAS_DEBUG_WX
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG
diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index de234e7..60a4ec2 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -154,3 +154,10 @@ static void via_no_dac(struct pci_dev *dev)
 DECLARE_PCI_FIXUP_CLASS_FINAL(PCI_VENDOR_ID_VIA, PCI_ANY_ID,
 				PCI_CLASS_BRIDGE_PCI, 8, via_no_dac);
 #endif
+
+#ifdef CONFIG_ARCH_HAS_TEARDOWN_DMA_OPS
+void arch_teardown_dma_ops(struct device *dev)
+{
+	set_dma_ops(dev, NULL);
+}
+#endif