[for-4.13] efi: do not use runtime services table with efi=no-rs
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Message ID 20191116234717.1458-1-marmarek@invisiblethingslab.com
State New
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  • [for-4.13] efi: do not use runtime services table with efi=no-rs
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Commit Message

Marek Marczykowski-Górecki Nov. 16, 2019, 11:47 p.m. UTC
Before dfcccc6631 "efi: use directmap to access runtime services table"
all usages of efi_rs pointer were guarded by efi_rs_enter(), which
implicitly refused to operate with efi=no-rs (by checking if
efi_l4_pgtable is NULL - which is the case for efi=no-rs). The said
commit (re)moved that call as unneeded for just reading content of
efi_rs structure - to avoid unnecessary page tables switch. But it
neglected to check if efi_rs access is legal.

Fix this by adding explicit check for runtime service being enabled in
the cases that do not use efi_rs_enter().

Reported-by: Roman Shaposhnik <roman@zededa.com>
Fixes: dfcccc6631 "efi: use directmap to access runtime services table"
Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
---
Cc: Juergen Gross <jgross@suse.com>
---
 xen/common/efi/runtime.c | 6 ++++++
 1 file changed, 6 insertions(+)

Comments

Jan Beulich Nov. 18, 2019, 11:27 a.m. UTC | #1
On 17.11.2019 00:47, Marek Marczykowski-Górecki  wrote:
> Before dfcccc6631 "efi: use directmap to access runtime services table"
> all usages of efi_rs pointer were guarded by efi_rs_enter(), which
> implicitly refused to operate with efi=no-rs (by checking if
> efi_l4_pgtable is NULL - which is the case for efi=no-rs). The said
> commit (re)moved that call as unneeded for just reading content of
> efi_rs structure - to avoid unnecessary page tables switch. But it
> neglected to check if efi_rs access is legal.
> 
> Fix this by adding explicit check for runtime service being enabled in
> the cases that do not use efi_rs_enter().
> 
> Reported-by: Roman Shaposhnik <roman@zededa.com>
> Fixes: dfcccc6631 "efi: use directmap to access runtime services table"
> Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>

Reviewed-by: Jan Beulich <jbeulich@suse.com>

Albeit I would have preferred ...

> @@ -613,6 +615,8 @@ int efi_runtime_call(struct xenpf_efi_runtime_call *op)
>              break;
>          }
>  
> +        if ( !efi_enabled(EFI_RS) )
> +            return -EOPNOTSUPP;
>          if ( (efi_rs->Hdr.Revision >> 16) < 2 )
>              return -EOPNOTSUPP;
>          state = efi_rs_enter();
> @@ -631,6 +635,8 @@ int efi_runtime_call(struct xenpf_efi_runtime_call *op)
>          if ( op->misc )
>              return -EINVAL;
>  
> +        if ( !efi_enabled(EFI_RS) )
> +            return -EOPNOTSUPP;
>          if ( (efi_rs->Hdr.Revision >> 16) < 2 )
>              return -EOPNOTSUPP;

... if these two pairs of if()-s would each have been folded; I may
take the liberty to do so while committing if I end up being the
committer of this.

Jan
Jürgen Groß Nov. 19, 2019, 4:55 p.m. UTC | #2
On 17.11.19 00:47, Marek Marczykowski-Górecki wrote:
> Before dfcccc6631 "efi: use directmap to access runtime services table"
> all usages of efi_rs pointer were guarded by efi_rs_enter(), which
> implicitly refused to operate with efi=no-rs (by checking if
> efi_l4_pgtable is NULL - which is the case for efi=no-rs). The said
> commit (re)moved that call as unneeded for just reading content of
> efi_rs structure - to avoid unnecessary page tables switch. But it
> neglected to check if efi_rs access is legal.
> 
> Fix this by adding explicit check for runtime service being enabled in
> the cases that do not use efi_rs_enter().
> 
> Reported-by: Roman Shaposhnik <roman@zededa.com>
> Fixes: dfcccc6631 "efi: use directmap to access runtime services table"
> Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>

Release-acked-by: Juergen Gross <jgross@suse.com>


Juergen

Patch
diff mbox series

diff --git a/xen/common/efi/runtime.c b/xen/common/efi/runtime.c
index 22fd6c9b53..12da6a525a 100644
--- a/xen/common/efi/runtime.c
+++ b/xen/common/efi/runtime.c
@@ -211,6 +211,8 @@  int efi_get_info(uint32_t idx, union xenpf_efi_info *info)
         break;
     case XEN_FW_EFI_RT_VERSION:
     {
+        if ( !efi_enabled(EFI_RS) )
+            return -EOPNOTSUPP;
         info->version = efi_rs->Hdr.Revision;
         break;
     }
@@ -613,6 +615,8 @@  int efi_runtime_call(struct xenpf_efi_runtime_call *op)
             break;
         }
 
+        if ( !efi_enabled(EFI_RS) )
+            return -EOPNOTSUPP;
         if ( (efi_rs->Hdr.Revision >> 16) < 2 )
             return -EOPNOTSUPP;
         state = efi_rs_enter();
@@ -631,6 +635,8 @@  int efi_runtime_call(struct xenpf_efi_runtime_call *op)
         if ( op->misc )
             return -EINVAL;
 
+        if ( !efi_enabled(EFI_RS) )
+            return -EOPNOTSUPP;
         if ( (efi_rs->Hdr.Revision >> 16) < 2 )
             return -EOPNOTSUPP;
         /* XXX fall through for now */