RE: [PATCH v2 1/1] ACPI / APEI: Fix for overwriting AER info when error status data has multiple sections

[Shiju Jose <shiju.jose@huawei.com>]

Hi Rafael,

>-----Original Message-----
>From: Rafael J. Wysocki <rafael@kernel.org>
>Sent: 20 September 2023 18:23
>To: Shiju Jose <shiju.jose@huawei.com>
>Cc: helgaas@kernel.org; rafael@kernel.org; lenb@kernel.org;
>tony.luck@intel.com; james.morse@arm.com; bp@alien8.de;
>ying.huang@intel.com; linux-acpi@vger.kernel.org; linux-pci@vger.kernel.org;
>linux-kernel@vger.kernel.org; Linuxarm <linuxarm@huawei.com>; Jonathan
>Cameron <jonathan.cameron@huawei.com>; tanxiaofei
><tanxiaofei@huawei.com>; Zengtao (B) <prime.zeng@hisilicon.com>
>Subject: Re: [PATCH v2 1/1] ACPI / APEI: Fix for overwriting AER info when error
>status data has multiple sections
>
>On Tue, Sep 19, 2023 at 11:16 AM <shiju.jose@huawei.com> wrote:
>>
>> From: Shiju Jose <shiju.jose@huawei.com>
>>
>> ghes_handle_aer() passes AER data to the PCI core for logging and
>> recovery by calling aer_recover_queue() with a pointer to struct
>> aer_capability_regs.
>>
>> The problem was that aer_recover_queue() queues the pointer directly
>> without copying the aer_capability_regs data.  The pointer was to the
>> ghes->estatus buffer, which could be reused before
>> aer_recover_work_func() reads the data.
>>
>> To avoid this problem, allocate a new aer_capability_regs structure
>> from the ghes_estatus_pool, copy the AER data from the ghes->estatus
>> buffer into it, pass a pointer to the new struct to
>> aer_recover_queue(), and free it after aer_recover_work_func() has
>> processed it.
>>
>> Reported-by: Bjorn Helgaas <helgaas@kernel.org>
>> Acked-by: Bjorn Helgaas <bhelgaas@google.com>
>> Signed-off-by: Shiju Jose <shiju.jose@huawei.com>
>> ---
>> Changes from v1 to v2:
>> 1. Updated patch description with the description Bjorn has suggested.
>> 2. Add Acked-by: Bjorn Helgaas <bhelgaas@google.com>.
>> ---
>>  drivers/acpi/apei/ghes.c | 23 ++++++++++++++++++++++-
>>  drivers/pci/pcie/aer.c   | 10 ++++++++++
>>  include/acpi/ghes.h      |  1 +
>>  3 files changed, 33 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c index
>> ef59d6ea16da..63ad0541db38 100644
>> --- a/drivers/acpi/apei/ghes.c
>> +++ b/drivers/acpi/apei/ghes.c
>> @@ -209,6 +209,20 @@ int ghes_estatus_pool_init(unsigned int num_ghes)
>>         return -ENOMEM;
>>  }
>>
>> +/**
>> + * ghes_estatus_pool_region_free - free previously allocated memory
>> + *                                from the ghes_estatus_pool.
>> + * @addr: address of memory to free.
>> + * @size: size of memory to free.
>> + *
>> + * Returns none.
>> + */
>> +void ghes_estatus_pool_region_free(unsigned long addr, u32 size) {
>> +       gen_pool_free(ghes_estatus_pool, addr, size); }
>> +EXPORT_SYMBOL_GPL(ghes_estatus_pool_region_free);
>> +
>>  static int map_gen_v2(struct ghes *ghes)  {
>>         return
>> apei_map_generic_address(&ghes->generic_v2->read_ack_register);
>> @@ -564,6 +578,7 @@ static void ghes_handle_aer(struct
>acpi_hest_generic_data *gdata)
>>             pcie_err->validation_bits & CPER_PCIE_VALID_AER_INFO) {
>>                 unsigned int devfn;
>>                 int aer_severity;
>> +               u8 *aer_info;
>>
>>                 devfn = PCI_DEVFN(pcie_err->device_id.device,
>>                                   pcie_err->device_id.function); @@
>> -577,11 +592,17 @@ static void ghes_handle_aer(struct
>acpi_hest_generic_data *gdata)
>>                 if (gdata->flags & CPER_SEC_RESET)
>>                         aer_severity = AER_FATAL;
>>
>> +               aer_info = (void *)gen_pool_alloc(ghes_estatus_pool,
>> +                                                 sizeof(struct aer_capability_regs));
>> +               if (!aer_info)
>> +                       return;
>> +               memcpy(aer_info, pcie_err->aer_info, sizeof(struct
>> + aer_capability_regs));
>> +
>>                 aer_recover_queue(pcie_err->device_id.segment,
>>                                   pcie_err->device_id.bus,
>>                                   devfn, aer_severity,
>>                                   (struct aer_capability_regs *)
>> -                                 pcie_err->aer_info);
>> +                                 aer_info);
>>         }
>>  #endif
>>  }
>> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c index
>> e85ff946e8c8..388b614c11fd 100644
>> --- a/drivers/pci/pcie/aer.c
>> +++ b/drivers/pci/pcie/aer.c
>> @@ -29,6 +29,7 @@
>>  #include <linux/kfifo.h>
>>  #include <linux/slab.h>
>>  #include <acpi/apei.h>
>> +#include <acpi/ghes.h>
>>  #include <ras/ras_event.h>
>>
>>  #include "../pci.h"
>> @@ -996,6 +997,15 @@ static void aer_recover_work_func(struct work_struct
>*work)
>>                         continue;
>>                 }
>>                 cper_print_aer(pdev, entry.severity, entry.regs);
>> +               /*
>> +                * Memory for aer_capability_regs(entry.regs) is being allocated
>from the
>> +                * ghes_estatus_pool to protect it from overwriting when multiple
>sections
>> +                * are present in the error status. Thus free the same after
>processing
>> +                * the data.
>> +                */
>> +               ghes_estatus_pool_region_free((unsigned long)entry.regs,
>> +                                             sizeof(struct
>> + aer_capability_regs));
>> +
>>                 if (entry.severity == AER_NONFATAL)
>>                         pcie_do_recovery(pdev, pci_channel_io_normal,
>>                                          aer_root_reset); diff --git
>> a/include/acpi/ghes.h b/include/acpi/ghes.h index
>> 3c8bba9f1114..40d89e161076 100644
>> --- a/include/acpi/ghes.h
>> +++ b/include/acpi/ghes.h
>> @@ -78,6 +78,7 @@ static inline struct list_head
>> *ghes_get_devices(void) { return NULL; }  #endif
>>
>>  int ghes_estatus_pool_init(unsigned int num_ghes);
>> +void ghes_estatus_pool_region_free(unsigned long addr, u32 size);
>
>If I'm not mistaken, this needs to go under #ifdef CONFIG_ACPI_APEI_GHES and
>it needs an empty stub for the case when CONFIG_ACPI_APEI_GHES is not set.

Thanks. You are right. It was fixed and is under build check for i386 and aarch64, 
testing etc.
I will post the updated patch soon. 
>
>>
>>  static inline int acpi_hest_get_version(struct acpi_hest_generic_data
>> *gdata)  {
>> --
>> 2.34.1
>>
Thanks,
Shiju