| Message ID | 20200522130145.30067-1-saiprakash.ranjan@codeaurora.org |
|---|---|
| State | New |
| Headers | show |
| Series | iommu: Fix group refcount in iommu_alloc_default_domain() | expand |
Hi Joerg, On 2020-05-25 18:32, Joerg Roedel wrote: > Hi, > > On Fri, May 22, 2020 at 06:31:45PM +0530, Sai Prakash Ranjan wrote: >> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c >> index a4c2f122eb8b..05f7b77c432f 100644 >> --- a/drivers/iommu/iommu.c >> +++ b/drivers/iommu/iommu.c >> @@ -1491,6 +1491,7 @@ static int iommu_alloc_default_domain(struct >> device *dev) >> { >> struct iommu_group *group; >> unsigned int type; >> + int ret; >> >> group = iommu_group_get(dev); >> if (!group) >> @@ -1501,7 +1502,11 @@ static int iommu_alloc_default_domain(struct >> device *dev) >> >> type = iommu_get_def_domain_type(dev); >> >> - return iommu_group_alloc_default_domain(dev->bus, group, type); >> + ret = iommu_group_alloc_default_domain(dev->bus, group, type); >> + >> + iommu_group_put(group); >> + >> + return ret; >> } >> >> /** > > Thanks for the report and the fix. I think it is better to fix this by > not taking a group reference in iommu_alloc_default_domain() at all and > pass group as a parameter. Please see the patch I just sent out. > Thanks for the patch, it looks like the right thing to do. Testing it out now. Thanks, Sai
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c index a4c2f122eb8b..05f7b77c432f 100644 --- a/drivers/iommu/iommu.c +++ b/drivers/iommu/iommu.c @@ -1491,6 +1491,7 @@ static int iommu_alloc_default_domain(struct device *dev) { struct iommu_group *group; unsigned int type; + int ret; group = iommu_group_get(dev); if (!group) @@ -1501,7 +1502,11 @@ static int iommu_alloc_default_domain(struct device *dev) type = iommu_get_def_domain_type(dev); - return iommu_group_alloc_default_domain(dev->bus, group, type); + ret = iommu_group_alloc_default_domain(dev->bus, group, type); + + iommu_group_put(group); + + return ret; } /**
Since the change to move default domain allocation to probe, there is a refcount decrement missing for the group in iommu_alloc_default_domain(). Because of this missing refcount decrement, the device is never released from the group as the devices_kobj refcount never reaches 0 in iommu_group_remove_device() leading to a lot of issues. One such case is that this will lead to a different group allocation on every reload of the module which configures iommu such as the ath10k module which then finally fails to attach this device to the SMMU with -ENOSPC error in __arm_smmu_alloc_bitmap() once the count of module reload crosses the number of context banks. This will then lead to NULL pointer deference in the next reload of the module. Add the missing refcount decrement(iommu_group_put()) in iommu_alloc_default_domain() to fix this issue. Call trace: <snip>... platform wifi-firmware.0: Adding to iommu group 82 ath10k_snoc 18800000.wifi: could not attach device: -28 platform wifi-firmware.0: Removing from iommu group 82 ath10k_snoc 18800000.wifi: failed to initialize firmware: -28 ath10k_snoc: probe of 18800000.wifi failed with error -28 platform wifi-firmware.0: Adding to iommu group 83 Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 Mem abort info: ESR = 0x96000006 EC = 0x25: DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 Data abort info: ISV = 0, ISS = 0x00000006 CM = 0, WnR = 0 user pgtable: 4k pages, 39-bit VAs, pgdp=0000000177a53000 [0000000000000000] pgd=00000001e74f5003, pud=00000001e74f5003, pmd=0000000000000000 Internal error: Oops: 96000006 [#1] PREEMPT SMP pstate: 60400009 (nZCv daif +PAN -UAO) arm_smmu_flush_iotlb_all+0x20/0x6c iommu_create_device_direct_mappings+0x17c/0x1d8 iommu_probe_device+0xc0/0x100 of_iommu_configure+0x108/0x240 of_dma_configure+0x130/0x1d0 ath10k_fw_init+0xc4/0x1c4 [ath10k_snoc] ath10k_snoc_probe+0x5cc/0x678 [ath10k_snoc] platform_drv_probe+0x90/0xb0 really_probe+0x134/0x2ec driver_probe_device+0x64/0xfc device_driver_attach+0x4c/0x6c __driver_attach+0xac/0xc0 bus_for_each_dev+0x8c/0xd4 driver_attach+0x2c/0x38 bus_add_driver+0xfc/0x1d0 driver_register+0x64/0xf8 __platform_driver_register+0x4c/0x58 init_module+0x20/0x1000 [ath10k_snoc] do_one_initcall+0x13c/0x2d0 do_init_module+0x58/0x1dc load_module+0xde0/0xf10 __arm64_sys_finit_module+0xb0/0xe0 el0_svc_common+0xa4/0x154 el0_svc_compat_handler+0x2c/0x38 el0_svc_compat+0x8/0x10 Code: d503201f f85b8268 b4000248 f8560e74 (f9400280) ---[ end trace e5c1470a584952a0 ]--- Kernel panic - not syncing: Fatal exception Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org> --- drivers/iommu/iommu.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)