[PATCH 1/2] efinet: correct closing of SNP protocol

[Heinrich Schuchardt]

In the context of the implementation of the EFI_LOAD_FILE2_PROTOCOL for
the initial ramdisk it was observed that opening the SNP protocol failed.
https://lists.gnu.org/archive/html/grub-devel/2021-10/msg00020.html
This is due to an incorrect call to CloseProtocol().

The first parameter of CloseProtocol() is the handle, not the interface.

We call OpenProtocol() with ControllerHandle = NULL. Hence we must also
call CloseProtcol with ControllerHandel = NULL.

Each call of OpenProtocol() for the same network card handle is expected to
return the same interface pointer. If we want to close the protocol which
we opened non-exclusively when searching for a card, we have to do this
before opening the protocol exclusively.

As there is no guarantee that we successfully open the protocol add checks
in the transmit and receive functions.

Reported-by: Andreas Schwab <schwab@linux-m68k.org>
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
---
 grub-core/net/drivers/efi/efinet.c | 32 ++++++++++++++++++++++--------
 1 file changed, 24 insertions(+), 8 deletions(-)

diff --git a/grub-core/net/drivers/efi/efinet.c 
b/grub-core/net/drivers/efi/efinet.c
index 5388f952b..3f2ff03f5 100644
--- a/grub-core/net/drivers/efi/efinet.c
+++ b/grub-core/net/drivers/efi/efinet.c
@@ -39,6 +39,8 @@ send_card_buffer (struct grub_net_card *dev,
   grub_uint64_t limit_time = grub_get_time_ms () + 4000;
   void *txbuf;
 
+  if (!net)
+    return grub_error (GRUB_ERR_IO, N_("couldn't send network packet"));
   if (dev->txbusy)
     while (1)
       {
@@ -101,6 +103,9 @@ get_card_packet (struct grub_net_card *dev)
   struct grub_net_buff *nb;
   int i;
 
+  if (!net)
+    return NULL;
+
   for (i = 0; i < 2; i++)
     {
       if (!dev->rcvbuf)
@@ -148,11 +153,23 @@ open_card (struct grub_net_card *dev)
 {
   grub_efi_simple_network_t *net;
 
-  /* Try to reopen SNP exlusively to close any active MNP protocol instance
-     that may compete for packet polling
+  if (dev->efi_net)
+    {
+      efi_call_4 (grub_efi_system_table->boot_services->close_protocol,
+                 dev->efi_handle, &net_io_guid,
+                 grub_efi_image_handle, 0);
+      dev->efi_net = NULL;
+    }
+  /*
+   * Try to reopen SNP exlusively to close any active MNP protocol instance
+   * that may compete for packet polling
    */
   net = grub_efi_open_protocol (dev->efi_handle, &net_io_guid,
                                GRUB_EFI_OPEN_PROTOCOL_BY_EXCLUSIVE);
+  /* If exclusively fails, try non-exclusively. */
+  if (!net)
+      net = grub_efi_open_protocol (dev->efi_handle, &net_io_guid,
+                                   GRUB_EFI_OPEN_PROTOCOL_GET_PROTOCOL);
   if (net)
     {
       if (net->mode->state == GRUB_EFI_NETWORK_STOPPED
@@ -192,13 +209,12 @@ open_card (struct grub_net_card *dev)
          efi_call_6 (net->receive_filters, net, filters, 0, 0, 0, NULL);
        }
 
-      efi_call_4 (grub_efi_system_table->boot_services->close_protocol,
-                 dev->efi_net, &net_io_guid,
-                 grub_efi_image_handle, dev->efi_handle);
       dev->efi_net = net;
+    } else {
+      return grub_error (GRUB_ERR_NET_NO_CARD, "%s: can't open protocol",
+                        dev->name);
     }
 
-  /* If it failed we just try to run as best as we can */
   return GRUB_ERR_NONE;
 }
 
@@ -208,8 +224,8 @@ close_card (struct grub_net_card *dev)
   efi_call_1 (dev->efi_net->shutdown, dev->efi_net);
   efi_call_1 (dev->efi_net->stop, dev->efi_net);
   efi_call_4 (grub_efi_system_table->boot_services->close_protocol,
-             dev->efi_net, &net_io_guid,
-             grub_efi_image_handle, dev->efi_handle);
+             dev->efi_handle, &net_io_guid,
+             grub_efi_image_handle, 0);
 }
 
 static struct grub_net_card_driver efidriver =
-- 
2.32.0