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From:   Brian Masney <masneyb@onstation.org>
To:     robdclark@gmail.com, bjorn.andersson@linaro.org, joro@8bytes.org
Cc:     agross@kernel.org, iommu@lists.linux-foundation.org,
        linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] iommu/qcom: fix NULL pointer dereference during probe deferral
Date:   Tue, 31 Dec 2019 22:39:49 -0500
Message-Id: <20200101033949.755-1-masneyb@onstation.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

When attempting to load the qcom-iommu driver, and an -EPROBE_DEFER
error occurs, the following attempted NULL pointer deference occurs:

    Unable to handle kernel NULL pointer dereference at virtual address 00000014
    pgd = (ptrval)
    [00000014] *pgd=00000000
    Internal error: Oops: 5 [#1] PREEMPT SMP ARM
    Modules linked in:
    CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.5.0-rc2-next-20191220-00008-g7e71398bac41-dirty #67
    Hardware name: Generic DT based system
    PC is at qcom_iommu_domain_free (./include/linux/pm_runtime.h:226
      linux/drivers/iommu/qcom_iommu.c:358)
    LR is at release_iommu_mapping (arch/arm/mm/dma-mapping.c:2141)
    pc : lr : psr: 60000013
    sp : ee89dc48  ip : 00000000  fp : c13a6684
    r10: c13a661c  r9 : 00000000  r8 : c13a1240
    r7 : fffffdfb  r6 : 00000000  r5 : edc32c80  r4 : edc32c9c
    r3 : 00000000  r2 : 00000001  r1 : 00000004  r0 : edc32c9c
    Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
    Control: 10c5787d  Table: 0020406a  DAC: 00000051
    Process swapper/0 (pid: 1, stack limit = 0x(ptrval))
    Stack: (0xee89dc48 to 0xee89e000)
    dc40:                   edc3cc10 edc31ba0 00000000 c0316af8 edc3cc10 edc31b80
    dc60: 00000000 c0319684 c14341ac edc3cc10 00000000 c083bd88 edc3cc10 c13a1240
    dc80: c083c2e8 c13a6684 c13a661c c13a6508 c13a661c c083c134 c13a1240 ee89dcec
    dca0: edc3cc10 00000000 ee89dcec c083c2e8 c13a6684 c13a661c c13a6508 c13a661c
    dcc0: c13a6684 c083a31c c13a6684 ee82a86c edc32538 c1304e48 edc3cc10 00000001
    dce0: edc3cc54 c083bc08 ee82a880 edc3cc10 00000001 c1304e48 edc3cc10 edc3cc10
    dd00: c13a69e8 c083b010 edc3cc10 00000000 eea1fc10 c0837aac 00000200 00000000
    dd20: 00000000 00000000 00000000 c1304e48 00000000 edc3cc00 eea1fc10 00000000
    dd40: 00000000 eeff42f4 00000000 00000001 00000000 c09e96e0 eeff42a4 00000000
    dd60: 00000000 00000000 eea1fc10 c09e98bc 00000001 eea1fc10 00000000 eea1fc10
    dd80: edc32980 c1391580 eea1fc10 00000001 eea1fc10 c0850f90 c2706d80 c14368c0
    dda0: 60000013 c1304e48 00000106 eeff42a4 eeff3fa0 00000000 00000000 eea1fc10
    ddc0: 00000001 c1248900 00000106 c09e9bd0 00000001 c0c2ee64 eea1fc00 eea1fc10
    dde0: eea1fc10 00000000 c13a5b70 00000000 c1248900 c081496c c1023d84 00000000
    de00: eeff3fa0 c2706ddc c2706ddc c1304e48 00000001 00000000 eea1fc10 c13a5b70
    de20: 00000000 c13a5b70 00000000 c1248900 00000106 c083dfb8 c14341ac eea1fc10
    de40: 00000000 c083be58 eea1fc10 c13a5b70 c13a5b70 c13a69e8 c12003ec c123a854
    de60: c1248900 c083c134 c1248900 c09e6f3c c0d8d514 eea1fc10 00000000 c13a5b70
    de80: c13a69e8 c12003ec c123a854 c1248900 00000106 c083c3e0 00000000 c13a5b70
    dea0: eea1fc10 c083c440 00000000 c13a5b70 c083c3e8 c083a23c 00000106 ee82a858
    dec0: eea052b4 c1304e48 c13a5b70 edc32900 00000000 c083b270 c1043084 c121d1d8
    dee0: ffffe000 c13a5b70 c121d1d8 ffffe000 00000000 c083cfcc c13ece60 c121d1d8
    df00: ffffe000 c0302f90 00000106 c034407c 00000000 c10e3a00 c1044dd0 c12003ec
    df20: 00000000 00000006 00000006 c0fbecac c0fada88 c0fada3c 00000000 efffcbf8
    df40: efffcc0d c1304e48 00000000 00000006 c13f9500 c1304e48 c123a830 00000007
    df60: c13f9500 c13f9500 c123a834 c1200f64 00000006 00000006 00000000 c12003ec
    df80: c0c28194 00000000 c0c28194 00000000 00000000 00000000 00000000 00000000
    dfa0: 00000000 c0c2819c 00000000 c03010e8 00000000 00000000 00000000 00000000
    dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
    dfe0: 00000000 00000000 00000000 00000000 00000013 00000000 00000000 00000000
    (qcom_iommu_domain_free) from release_iommu_mapping (arch/arm/mm/dma-mapping.c:2141)
    (release_iommu_mapping) from arch_teardown_dma_ops (./include/linux/dma-mapping.h:271
      linux/arch/arm/mm/dma-mapping.c:2335)
    (arch_teardown_dma_ops) from really_probe (drivers/base/dd.c:607)
    (really_probe) from driver_probe_device (drivers/base/dd.c:721)
    (driver_probe_device) from bus_for_each_drv (drivers/base/bus.c:431)
    (bus_for_each_drv) from __device_attach (drivers/base/dd.c:896)
    (__device_attach) from bus_probe_device (drivers/base/bus.c:491)
    (bus_probe_device) from device_add (drivers/base/core.c:2488)
    (device_add) from of_platform_device_create_pdata (drivers/of/platform.c:189)
    (of_platform_device_create_pdata) from of_platform_bus_create
      (drivers/of/platform.c:393 linux/drivers/of/platform.c:346)
    (of_platform_bus_create) from of_platform_populate (drivers/of/platform.c:486)
    (of_platform_populate) from msm_pdev_probe (drivers/gpu/drm/msm/msm_drv.c:1197
      linux/drivers/gpu/drm/msm/msm_drv.c:1281)
    (msm_pdev_probe) from platform_drv_probe (drivers/base/platform.c:726)
    (platform_drv_probe) from really_probe (drivers/base/dd.c:553)
    (really_probe) from driver_probe_device (drivers/base/dd.c:721)
    (driver_probe_device) from device_driver_attach (drivers/base/dd.c:995)
    (device_driver_attach) from __driver_attach (drivers/base/dd.c:1074)
    (__driver_attach) from bus_for_each_dev (drivers/base/bus.c:304)
    (bus_for_each_dev) from bus_add_driver (drivers/base/bus.c:623)
    (bus_add_driver) from driver_register (drivers/base/driver.c:172)
    (driver_register) from do_one_initcall (./include/linux/compiler.h:232
      linux/./include/linux/jump_label.h:254
      linux/./include/linux/jump_label.h:264
      linux/./include/trace/events/initcall.h:48 linux/init/main.c:941)
    (do_one_initcall) from kernel_init_freeable (init/main.c:1013
      linux/init/main.c:1022 linux/init/main.c:1039
      linux/init/main.c:1231)
    (kernel_init_freeable) from kernel_init (init/main.c:1127)
    (kernel_init) from ret_from_fork (arch/arm/kernel/entry-common.S:156)
    Exception stack(0xee89dfb0 to 0xee89dff8)
    dfa0:                                     00000000 00000000 00000000 00000000
    dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
    dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
    Code: e92d4070 e1a04000 e3a01004 e240501c (e5930014)
    All code
    ========
       0:	70 40                	jo     0x42
       2:	2d e9 00 40 a0       	sub    $0xa04000e9,%eax
       7:	e1 04                	loope  0xd
       9:	10 a0 e3 1c 50 40    	adc    %ah,0x40501ce3(%rax)
       f:	e2 14                	loop   0x25
      11:*	00                   	.byte 0x0		<-- trapping instruction
      12:	93                   	xchg   %eax,%ebx
      13:	e5                   	.byte 0xe5

    Code starting with the faulting instruction
    ===========================================
       0:	14 00                	adc    $0x0,%al
       2:	93                   	xchg   %eax,%ebx
       3:	e5                   	.byte 0xe5

qcom_iommu_domain_free() has a WARN_ON() that checks to see if the value
of iommu is NULL and returns early, so iommu->dev will always be NULL.
qcom_iommu_detach_dev() is called prior to freeing the IOMMU domain and
is what sets the iommu member to NULL.

Let's fix this by adding the 'struct dev' pointer to the
qcom_iommu_domain struct.

Signed-off-by: Brian Masney <masneyb@onstation.org>
Fixes: 0ae349a0f33fb ("iommu/qcom: Add qcom_iommu")
---
 drivers/iommu/qcom_iommu.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/qcom_iommu.c b/drivers/iommu/qcom_iommu.c
index 52f38292df5b..ac4354773c06 100644
--- a/drivers/iommu/qcom_iommu.c
+++ b/drivers/iommu/qcom_iommu.c
@@ -65,6 +65,7 @@ struct qcom_iommu_domain {
 	struct mutex		 init_mutex; /* Protects iommu pointer */
 	struct iommu_domain	 domain;
 	struct qcom_iommu_dev	*iommu;
+	struct device		*dev;
 };
 
 static struct qcom_iommu_domain *to_qcom_iommu_domain(struct iommu_domain *dom)
@@ -243,6 +244,13 @@ static int qcom_iommu_init_domain(struct iommu_domain *domain,
 	};
 
 	qcom_domain->iommu = qcom_iommu;
+
+	/*
+	 * This dev pointer is needed to avoid a NULL pointer dereference in
+	 * qcom_iommu_domain_free().
+	 */
+	qcom_domain->dev = qcom_iommu->dev;
+
 	pgtbl_ops = alloc_io_pgtable_ops(ARM_32_LPAE_S1, &pgtbl_cfg, fwspec);
 	if (!pgtbl_ops) {
 		dev_err(qcom_iommu->dev, "failed to allocate pagetable ops\n");
@@ -355,11 +363,11 @@ static void qcom_iommu_domain_free(struct iommu_domain *domain)
 	 * cannot rely on the device_link.  Make sure the IOMMU is on to
 	 * avoid unclocked accesses in the TLB inv path:
 	 */
-	pm_runtime_get_sync(qcom_domain->iommu->dev);
+	pm_runtime_get_sync(qcom_domain->dev);
 
 	free_io_pgtable_ops(qcom_domain->pgtbl_ops);
 
-	pm_runtime_put_sync(qcom_domain->iommu->dev);
+	pm_runtime_put_sync(qcom_domain->dev);
 
 	kfree(qcom_domain);
 }
-- 
2.21.0