hw/uefi: fix size negotiation

Payload size is the variable request size, not the total buffer size.
Take that into account and subtract header sizes.

Fixes: db1ecfb473ac ("hw/uefi: add var-service-vars.c")
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-ID: <20260114104745.3465860-1-kraxel@redhat.com>

diff --git a/hw/uefi/var-service-vars.c b/hw/uefi/var-service-vars.c
index 52845e9723d3d818b5e2ecb9ac2651da42ff2f92..94f40ef23684f0ddbc43c4bfbca34a49c4922e31 100644 (file)
--- a/hw/uefi/var-service-vars.c
+++ b/hw/uefi/var-service-vars.c
@@ -593,7 +593,7 @@ uefi_vars_mm_get_payload_size(uefi_vars_state *uv, mm_header *mhdr,
         return uefi_vars_mm_error(mhdr, mvar, EFI_BAD_BUFFER_SIZE);
     }
 
-    ps->payload_size = uv->buf_size;
+    ps->payload_size = uv->buf_size - sizeof(*mhdr) - sizeof(*mvar);
     mvar->status = EFI_SUCCESS;
     return length;
 }