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

[Rafael J. Wysocki]

On Tue, Sep 19, 2023 at 11:16 AM <shiju.jose@xxxxxxxxxx> wrote:
>
> From: Shiju Jose <shiju.jose@xxxxxxxxxx>
>
> 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@xxxxxxxxxx>
> Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> Signed-off-by: Shiju Jose <shiju.jose@xxxxxxxxxx>
> ---
> Changes from v1 to v2:
> 1. Updated patch description with the description Bjorn has suggested.
> 2. Add Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>.
> ---
>  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.

>
>  static inline int acpi_hest_get_version(struct acpi_hest_generic_data *gdata)
>  {
> --
> 2.34.1
>