efi/efinet: Don't close connections at fini_hw() time

When GRUB runs on top of EFI firmware, it only has access to block and
network device abstractions exposed by the firmware, and it is up to the
firmware to quiesce the underlying hardware when exiting boot services
and handing over to the OS.

This is especially important for network devices, to prevent incoming
packets from being DMA'd straight into memory after the OS has taken
over but before it has managed to reconfigure the network hardware.

GRUB handles this by means of the grub_net_fini_hw() preboot hook, which
is executed before calling into the booted image. This means that all
network devices disappear or become inoperable before the EFI stub
executes on EFI targeted builds. This is problematic as it prevents the
EFI stub from calling back into GRUB provided protocols such as
LoadFile2 for the initrd, which we will provide in a subsequent patch.

So add a flag that indicates to the network core that EFI network
devices should not be closed when grub_net_fini_hw() is called.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

diff --git a/grub-core/net/drivers/efi/efinet.c b/grub-core/net/drivers/efi/efinet.c
index 73343d26d9e10132816bc944e8de53d0d7b1a405..5adf5f40f4924b2e4381330e8c20f99c6476cb85 100644 (file)
--- a/grub-core/net/drivers/efi/efinet.c
+++ b/grub-core/net/drivers/efi/efinet.c
@@ -320,7 +320,15 @@ grub_efinet_findcards (void)
 
       card->name = grub_xasprintf ("efinet%d", i++);
       card->driver = &efidriver;
-      card->flags = 0;
+      /*
+       * EFI network devices are abstract SNP protocol instances, and the
+       * firmware is in charge of ensuring that they will be torn down when the
+       * OS loader hands off to the OS proper. Closing them as part of the
+       * preboot cleanup is therefore unnecessary, and undesirable, as it
+       * prevents us from using the network connection in a protocal callback
+       * such as LoadFile2 for initrd loading.
+       */
+      card->flags = GRUB_NET_CARD_NO_CLOSE_ON_FINI_HW;
       card->default_address.type = GRUB_NET_LINK_LEVEL_PROTOCOL_ETHERNET;
       grub_memcpy (card->default_address.mac,
                   net->mode->current_address,

diff --git a/grub-core/net/net.c b/grub-core/net/net.c
index 064e7114e012541c7828677b2458394c949c3019..7046dc57890aac3055311c25af70a59538adb632 100644 (file)
--- a/grub-core/net/net.c
+++ b/grub-core/net/net.c
@@ -1787,7 +1787,7 @@ grub_net_fini_hw (int noreturn __attribute__ ((unused)))
 {
   struct grub_net_card *card;
   FOR_NET_CARDS (card)
-    if (card->opened)
+    if (card->opened && !(card->flags & GRUB_NET_CARD_NO_CLOSE_ON_FINI_HW))
       {
        if (card->driver->close)
          card->driver->close (card);

diff --git a/include/grub/net.h b/include/grub/net.h
index a64a04cc80b170f3f5e98b96a2ab5d53b3819b84..79cba357ae6a85b8997e9c77e473f9800d697358 100644 (file)
--- a/include/grub/net.h
+++ b/include/grub/net.h
@@ -64,7 +64,8 @@ typedef enum grub_net_interface_flags
 typedef enum grub_net_card_flags
   {
     GRUB_NET_CARD_HWADDRESS_IMMUTABLE = 1,
-    GRUB_NET_CARD_NO_MANUAL_INTERFACES = 2
+    GRUB_NET_CARD_NO_MANUAL_INTERFACES = 2,
+    GRUB_NET_CARD_NO_CLOSE_ON_FINI_HW = 4
   } grub_net_card_flags_t;
 
 struct grub_net_card;