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authorJohn Stultz <john.stultz@linaro.org>2020-10-31 00:25:49 +0000
committerJohn Stultz <john.stultz@linaro.org>2021-05-10 19:53:26 +0000
commitcd94f002237807d337ae8abec32066f1c8ba8cfe (patch)
treed7a314dc488f95f7034b16769383dd3596448e70
parentad0bb1713387ad3f1f7797a63184e24175301802 (diff)
downloadandroid-dev-cd94f002237807d337ae8abec32066f1c8ba8cfe.tar.gz
iommu: Avoid crash if iommu_group is null
In trying to handle a possible driver probe ordering issue brought up by Robin Murphy, I ran across a separate null pointer crash in the iommu core in iommu_group_remove_device(): [ 2.732803] dwc3-qcom a6f8800.usb: failed to get usb-ddr path: -517 [ 2.739281] Unable to handle kernel NULL pointer dereference at virtual address 00000000000000c0 ... [ 2.775619] [00000000000000c0] user address but active_mm is swapper [ 2.782039] Internal error: Oops: 96000005 [#1] PREEMPT SMP [ 2.787670] Modules linked in: [ 2.790769] CPU: 6 PID: 1 Comm: swapper/0 Tainted: G W 5.10.0-rc1-mainline-00025-g272a618fc36-dirty #3973 [ 2.801719] Hardware name: Thundercomm Dragonboard 845c (DT) [ 2.807431] pstate: 00c00005 (nzcv daif +PAN +UAO -TCO BTYPE=--) [ 2.813508] pc : iommu_group_remove_device+0x30/0x1b0 [ 2.818611] lr : iommu_release_device+0x4c/0x78 [ 2.823189] sp : ffffffc01005b950 ... [ 2.907082] Call trace: [ 2.909566] iommu_group_remove_device+0x30/0x1b0 [ 2.914323] iommu_release_device+0x4c/0x78 [ 2.918559] iommu_bus_notifier+0xe8/0x108 [ 2.922708] blocking_notifier_call_chain+0x78/0xb8 [ 2.927641] device_del+0x2ac/0x3d0 [ 2.931177] platform_device_del.part.9+0x20/0x98 [ 2.935933] platform_device_unregister+0x2c/0x40 [ 2.940694] of_platform_device_destroy+0xd8/0xe0 [ 2.945450] device_for_each_child_reverse+0x58/0xb0 [ 2.950471] of_platform_depopulate+0x4c/0x78 [ 2.954886] dwc3_qcom_probe+0x93c/0xcb8 [ 2.958858] platform_drv_probe+0x58/0xa8 [ 2.962917] really_probe+0xec/0x398 [ 2.966531] driver_probe_device+0x5c/0xb8 [ 2.970677] device_driver_attach+0x74/0x98 [ 2.974911] __driver_attach+0x60/0xe8 [ 2.978700] bus_for_each_dev+0x84/0xd8 [ 2.982581] driver_attach+0x30/0x40 [ 2.986194] bus_add_driver+0x160/0x208 [ 2.990076] driver_register+0x64/0x110 [ 2.993957] __platform_driver_register+0x58/0x68 [ 2.998716] dwc3_qcom_driver_init+0x20/0x28 [ 3.003041] do_one_initcall+0x6c/0x2d0 [ 3.006925] kernel_init_freeable+0x214/0x268 [ 3.011339] kernel_init+0x18/0x118 [ 3.014876] ret_from_fork+0x10/0x18 [ 3.018495] Code: d0006a21 f9417295 91130021 910162b6 (b940c2a2) In the case above, the arm-smmu driver fails to probe with EPROBE_DEFER, and I'm guessing I'm guessing that causes iommu_group_add_device() to fail and sets the dev->iommu_group = NULL, then somehow we hit iommu_group_remove_device() and trip over the null value? I'm not really sure... Anyway, adding the null check seems to avoid the issue and the system boots fine after the arm-smmu driver later reprobed. Feedback or better ideas for a solution would be appreciated! Cc: Robin Murphy <robin.murphy@arm.com> Cc: Will Deacon <will@kernel.org> Cc: Andy Gross <agross@kernel.org> Cc: Maulik Shah <mkshah@codeaurora.org> Cc: Bjorn Andersson <bjorn.andersson@linaro.org> Cc: Saravana Kannan <saravanak@google.com> Cc: Marc Zyngier <maz@kernel.org> Cc: Lina Iyer <ilina@codeaurora.org> Cc: iommu@lists.linux-foundation.org Cc: linux-arm-msm <linux-arm-msm@vger.kernel.org> Signed-off-by: John Stultz <john.stultz@linaro.org> Change-Id: I7d866b117cb3b4f2f51e09cd844538a267b2d8be
-rw-r--r--drivers/iommu/iommu.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 808ab70d5df5..f56a62149ef0 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -924,6 +924,10 @@ void iommu_group_remove_device(struct device *dev)
struct iommu_group *group = dev->iommu_group;
struct group_device *tmp_device, *device = NULL;
+ /* Avoid crash if iommu_group value is null */
+ if (!group)
+ return;
+
dev_info(dev, "Removing from iommu group %d\n", group->id);
/* Pre-notify listeners that a device is being removed. */