CVE-2022-48796

In the Linux kernel, the following vulnerability has been resolved:

iommu: Fix potential use-after-free during probe

Kasan has reported the following use after free on dev->iommu.

when a device probe fails and it is in process of freeing dev->iommu

in dev_iommu_free function, a deferred_probe_work_func runs in parallel

and tries to access dev->iommu->fwspec in of_iommu_configure path thus

causing use after free.

BUG: KASAN: use-after-free in of_iommu_configure+0xb4/0x4a4

Read of size 8 at addr ffffff87a2f1acb8 by task kworker/u16:2/153

Workqueue: events_unbound deferred_probe_work_func

Call trace:

dump_backtrace+0x0/0x33c

show_stack+0x18/0x24

dump_stack_lvl+0x16c/0x1e0

print_address_description+0x84/0x39c

__kasan_report+0x184/0x308

kasan_report+0x50/0x78

__asan_load8+0xc0/0xc4

of_iommu_configure+0xb4/0x4a4

of_dma_configure_id+0x2fc/0x4d4

platform_dma_configure+0x40/0x5c

really_probe+0x1b4/0xb74

driver_probe_device+0x11c/0x228

__device_attach_driver+0x14c/0x304

bus_for_each_drv+0x124/0x1b0

__device_attach+0x25c/0x334

device_initial_probe+0x24/0x34

bus_probe_device+0x78/0x134

deferred_probe_work_func+0x130/0x1a8

process_one_work+0x4c8/0x970

worker_thread+0x5c8/0xaec

kthread+0x1f8/0x220

ret_from_fork+0x10/0x18

Allocated by task 1:

____kasan_kmalloc+0xd4/0x114

__kasan_kmalloc+0x10/0x1c

kmem_cache_alloc_trace+0xe4/0x3d4

__iommu_probe_device+0x90/0x394

probe_iommu_group+0x70/0x9c

bus_for_each_dev+0x11c/0x19c

bus_iommu_probe+0xb8/0x7d4

bus_set_iommu+0xcc/0x13c

arm_smmu_bus_init+0x44/0x130 [arm_smmu]

arm_smmu_device_probe+0xb88/0xc54 [arm_smmu]

platform_drv_probe+0xe4/0x13c

really_probe+0x2c8/0xb74

driver_probe_device+0x11c/0x228

device_driver_attach+0xf0/0x16c

__driver_attach+0x80/0x320

bus_for_each_dev+0x11c/0x19c

driver_attach+0x38/0x48

bus_add_driver+0x1dc/0x3a4

driver_register+0x18c/0x244

__platform_driver_register+0x88/0x9c

init_module+0x64/0xff4 [arm_smmu]

do_one_initcall+0x17c/0x2f0

do_init_module+0xe8/0x378

load_module+0x3f80/0x4a40

__se_sys_finit_module+0x1a0/0x1e4

__arm64_sys_finit_module+0x44/0x58

el0_svc_common+0x100/0x264

do_el0_svc+0x38/0xa4

el0_svc+0x20/0x30

el0_sync_handler+0x68/0xac

el0_sync+0x160/0x180

Freed by task 1:

kasan_set_track+0x4c/0x84

kasan_set_free_info+0x28/0x4c

____kasan_slab_free+0x120/0x15c

__kasan_slab_free+0x18/0x28

slab_free_freelist_hook+0x204/0x2fc

kfree+0xfc/0x3a4

__iommu_probe_device+0x284/0x394

probe_iommu_group+0x70/0x9c

bus_for_each_dev+0x11c/0x19c

bus_iommu_probe+0xb8/0x7d4

bus_set_iommu+0xcc/0x13c

arm_smmu_bus_init+0x44/0x130 [arm_smmu]

arm_smmu_device_probe+0xb88/0xc54 [arm_smmu]

platform_drv_probe+0xe4/0x13c

really_probe+0x2c8/0xb74

driver_probe_device+0x11c/0x228

device_driver_attach+0xf0/0x16c

__driver_attach+0x80/0x320

bus_for_each_dev+0x11c/0x19c

driver_attach+0x38/0x48

bus_add_driver+0x1dc/0x3a4

driver_register+0x18c/0x244

__platform_driver_register+0x88/0x9c

init_module+0x64/0xff4 [arm_smmu]

do_one_initcall+0x17c/0x2f0

do_init_module+0xe8/0x378

load_module+0x3f80/0x4a40

__se_sys_finit_module+0x1a0/0x1e4

__arm64_sys_finit_module+0x44/0x58

el0_svc_common+0x100/0x264

do_el0_svc+0x38/0xa4

el0_svc+0x20/0x30

el0_sync_handler+0x68/0xac

el0_sync+0x160/0x180

Fix this by setting dev->iommu to NULL first and

then freeing dev_iommu structure in dev_iommu_free

function.