Re: [PATCH 4/4] powerpc/pseries: Implement signed update for PLPKS objects

[Russell Currey <ruscur@russell.cc>]

On Tue, 2022-12-20 at 18:16 +1100, Andrew Donnellan wrote:
> From: Nayna Jain <nayna@linux.ibm.com>
> 
> The Platform Keystore provides a signed update interface which can be
> used
> to create, replace or append to certain variables in the PKS in a
> secure
> fashion, with the hypervisor requiring that the update be signed
> using the
> Platform Key.
> 
> Implement an interface to the H_PKS_SIGNED_UPDATE hcall in the plpks
> driver to allow signed updates to PKS objects.
> 
> (The plpks driver doesn't need to do any cryptography or otherwise
> handle
> the actual signed variable contents - that will be handled by
> userspace
> tooling.)
> 
> Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
> [ajd: split patch, rewrite commit message, add timeout handling]
> Co-developed-by: Andrew Donnellan <ajd@linux.ibm.com>
> Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>
> ---
>  arch/powerpc/include/asm/hvcall.h      |  3 +-
>  arch/powerpc/platforms/pseries/plpks.c | 81 +++++++++++++++++++++++-
> --
>  arch/powerpc/platforms/pseries/plpks.h |  5 ++
>  3 files changed, 79 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/hvcall.h
> b/arch/powerpc/include/asm/hvcall.h
> index 95fd7f9485d5..33b26c0cb69b 100644
> --- a/arch/powerpc/include/asm/hvcall.h
> +++ b/arch/powerpc/include/asm/hvcall.h
> @@ -336,7 +336,8 @@
>  #define H_SCM_FLUSH            0x44C
>  #define H_GET_ENERGY_SCALE_INFO        0x450
>  #define H_WATCHDOG             0x45C
> -#define MAX_HCALL_OPCODE       H_WATCHDOG
> +#define H_PKS_SIGNED_UPDATE    0x454
> +#define MAX_HCALL_OPCODE       H_PKS_SIGNED_UPDATE
>  
>  /* Scope args for H_SCM_UNBIND_ALL */
>  #define H_UNBIND_SCOPE_ALL (0x1)
> diff --git a/arch/powerpc/platforms/pseries/plpks.c
> b/arch/powerpc/platforms/pseries/plpks.c
> index c5ae00a8a968..9e4401aabf4f 100644
> --- a/arch/powerpc/platforms/pseries/plpks.c
> +++ b/arch/powerpc/platforms/pseries/plpks.c
> @@ -30,9 +30,9 @@
>  #define MAX_NAME_SIZE      239
>  #define MAX_DATA_SIZE      4000
>  
> -#define PKS_FLUSH_MAX_TIMEOUT 5000 //msec
> -#define PKS_FLUSH_SLEEP              10 //msec
> -#define PKS_FLUSH_SLEEP_RANGE 400
> +#define PKS_MAX_TIMEOUT                5000 // msec
> +#define PKS_FLUSH_SLEEP                10 // msec
> +#define PKS_FLUSH_SLEEP_RANGE  400
>  
>  static u8 *ospassword;
>  static u16 ospasswordlength;
> @@ -95,6 +95,12 @@ static int pseries_status_to_err(int rc)
>                 err = -ENOENT;
>                 break;
>         case H_BUSY:
> +       case H_LONG_BUSY_ORDER_1_MSEC:
> +       case H_LONG_BUSY_ORDER_10_MSEC:
> +       case H_LONG_BUSY_ORDER_100_MSEC:
> +       case H_LONG_BUSY_ORDER_1_SEC:
> +       case H_LONG_BUSY_ORDER_10_SEC:
> +       case H_LONG_BUSY_ORDER_100_SEC:
>                 err = -EBUSY;
>                 break;
>         case H_AUTHORITY:
> @@ -198,14 +204,17 @@ static struct label *construct_label(char
> *component, u8 varos, u8 *name,
>                                      u16 namelen)
>  {
>         struct label *label;
> -       size_t slen;
> +       size_t slen = 0;
>  
>         if (!name || namelen > MAX_NAME_SIZE)
>                 return ERR_PTR(-EINVAL);
>  
> -       slen = strlen(component);
> -       if (component && slen > sizeof(label->attr.prefix))
> -               return ERR_PTR(-EINVAL);
> +       // Support NULL component for signed updates
> +       if (component) {
> +               slen = strlen(component);
> +               if (slen > sizeof(label->attr.prefix))
> +                       return ERR_PTR(-EINVAL);
> +       }
>  
>         // The label structure must not cross a page boundary, so we
> align to the next power of 2
>         label = kzalloc(roundup_pow_of_two(sizeof(*label)),
> GFP_KERNEL);
> @@ -372,7 +381,7 @@ static int plpks_confirm_object_flushed(struct
> label *label,
>                 usleep_range(PKS_FLUSH_SLEEP,
>                              PKS_FLUSH_SLEEP +
> PKS_FLUSH_SLEEP_RANGE);
>                 timeout = timeout + PKS_FLUSH_SLEEP;
> -       } while (timeout < PKS_FLUSH_MAX_TIMEOUT);
> +       } while (timeout < PKS_MAX_TIMEOUT);
>  
>         if (timed_out)
>                 rc = -ETIMEDOUT;
> @@ -382,6 +391,60 @@ static int plpks_confirm_object_flushed(struct
> label *label,
>         return rc;
>  }
>  
> +int plpks_signed_update_var(struct plpks_var var, u64 flags)
> +{
> +       unsigned long retbuf[PLPAR_HCALL9_BUFSIZE] = {0};
> +       int rc;
> +       struct label *label;
> +       struct plpks_auth *auth;
> +       u64 continuetoken = 0;
> +       u64 timeout = 0;
> +
> +       if (!var.data || var.datalen <= 0 || var.namelen >
> MAX_NAME_SIZE)
> +               return -EINVAL;
> +
> +       if (!(var.policy & SIGNEDUPDATE))
> +               return -EINVAL;
> +
> +       auth = construct_auth(PKS_OS_OWNER);
> +       if (IS_ERR(auth))
> +               return PTR_ERR(auth);
> +
> +       label = construct_label(var.component, var.os, var.name,
> var.namelen);
> +       if (IS_ERR(label)) {
> +               rc = PTR_ERR(label);
> +               goto out;
> +       }
> +
> +       do {
> +               rc = plpar_hcall9(H_PKS_SIGNED_UPDATE, retbuf,
> +                                 virt_to_phys(auth),
> virt_to_phys(label),
> +                                 label->size, var.policy, flags,
> +                                 virt_to_phys(var.data),
> var.datalen,
> +                                 continuetoken);
> +
> +               continuetoken = retbuf[0];
> +               if (pseries_status_to_err(rc) == -EBUSY) {
> +                       int delay_ms = get_longbusy_msecs(rc);
> +                       mdelay(delay_ms);
> +                       timeout += delay_ms;
> +               }
> +               rc = pseries_status_to_err(rc);
> +       } while (rc == -EBUSY && timeout < PKS_MAX_TIMEOUT);
> +
> +       if (!rc) {
> +               rc = plpks_confirm_object_flushed(label, auth);
> +               rc = pseries_status_to_err(rc);

Doesn't plpks_confirm_object_flushed() already return a Linux-friendly
error code?  If I'm reading this right, we'd be replacing any non-zero
return code with -EINVAL.

> +       }
> +
> +       kfree(label);
> +out:
> +       kfree(auth);
> +
> +       return rc;
> +}
> +EXPORT_SYMBOL(plpks_signed_update_var);
> +
>  int plpks_write_var(struct plpks_var var)
>  {
>         unsigned long retbuf[PLPAR_HCALL_BUFSIZE] = { 0 };
> @@ -428,7 +491,7 @@ int plpks_remove_var(char *component, u8 varos,
> struct plpks_var_name vname)
>         struct label *label;
>         int rc;
>  
> -       if (!component || vname.namelen > MAX_NAME_SIZE)
> +       if (vname.namelen > MAX_NAME_SIZE)
>                 return -EINVAL;
>  
>         auth = construct_auth(PKS_OS_OWNER);
> diff --git a/arch/powerpc/platforms/pseries/plpks.h
> b/arch/powerpc/platforms/pseries/plpks.h
> index c89740796660..33cf12809392 100644
> --- a/arch/powerpc/platforms/pseries/plpks.h
> +++ b/arch/powerpc/platforms/pseries/plpks.h
> @@ -40,6 +40,11 @@ struct plpks_var_name_list {
>         struct plpks_var_name varlist[];
>  };
>  
> +/**
> + * Updates the authenticated variable. It expects NULL as the
> component.
> + */
> +int plpks_signed_update_var(struct plpks_var var, u64 flags);
> +
>  /**
>   * Writes the specified var and its data to PKS.
>   * Any caller of PKS driver should present a valid component type
> for