[PATCH v4 2/3] venus: handle use after free for iommu_map/iommu_unmap

Mansur Alisha Shaik
2020-09-16T08:50:08Z

In concurrency usecase and reboot scenario we are seeing muliple
crashes related to iommu_map/iommu_unamp of core->fw.iommu_domain.

In one case we are seeing "Unable to handle kernel NULL pointer
dereference at virtual address 0000000000000008" crash, this is
because of core->fw.iommu_domain in venus_firmware_deinit() and
trying to map in venus_boot() during venus_sys_error_handler()

Call trace:
__iommu_map+0x4c/0x348
iommu_map+0x5c/0x70
venus_boot+0x184/0x230 [venus_core]
venus_sys_error_handler+0xa0/0x14c [venus_core]
process_one_work+0x210/0x3d0
worker_thread+0x248/0x3f4
kthread+0x11c/0x12c
ret_from_fork+0x10/0x18

In second case we are seeing "Unable to handle kernel paging request
at virtual address 006b6b6b6b6b6b9b" crash, this is because of
unmappin iommu domain which is already unmapped.

Call trace:
venus_remove+0xf8/0x108 [venus_core]
venus_core_shutdown+0x1c/0x34 [venus_core]
platform_drv_shutdown+0x28/0x34
device_shutdown+0x154/0x1fc
kernel_restart_prepare+0x40/0x4c
kernel_restart+0x1c/0x64
__arm64_sys_reboot+0x190/0x238
el0_svc_common+0xa4/0x154
el0_svc_compat_handler+0x2c/0x38
el0_svc_compat+0x8/0x10

Signed-off-by: Mansur Alisha Shaik <mansur@codeaurora.org>
---
drivers/media/platform/qcom/venus/firmware.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/drivers/media/platform/qcom/venus/firmware.c b/drivers/media/platform/qcom/venus/firmware.c
index 1db64a8..d03e2dd 100644
--- a/drivers/media/platform/qcom/venus/firmware.c
+++ b/drivers/media/platform/qcom/venus/firmware.c
@@ -171,9 +171,14 @@ static int venus_shutdown_no_tz(struct venus_core *core)

iommu = core->fw.iommu_domain;

- unmapped = iommu_unmap(iommu, VENUS_FW_START_ADDR, mapped);
- if (unmapped != mapped)
- dev_err(dev, "failed to unmap firmware\n");
+ if (core->fw.mapped_mem_size && iommu) {
+ unmapped = iommu_unmap(iommu, VENUS_FW_START_ADDR, mapped);
+
+ if (unmapped != mapped)
+ dev_err(dev, "failed to unmap firmware\n");
+ else
+ core->fw.mapped_mem_size = 0;
+ }

return 0;
}
@@ -305,7 +310,11 @@ void venus_firmware_deinit(struct venus_core *core)
iommu = core->fw.iommu_domain;

iommu_detach_device(iommu, core->fw.dev);
- iommu_domain_free(iommu);
+
+ if (core->fw.iommu_domain) {
+ iommu_domain_free(iommu);
+ core->fw.iommu_domain = NULL;
+ }

platform_device_unregister(to_platform_device(core->fw.dev));
}