On 12/6/24 13:27, Adriano Cordova wrote:
This commit fixes an use after free introduced in Commit e55a4acb54
(" efi_loader: net: set EFI bootdevice device path to HTTP when loaded
from wget"). The logic in efi_net_set_dp is reworked so that when the
function is invoked it not only changes the value of the static variable
net_dp (this is how the function was implemented in e55a4acb54) but also
updates the protocol interface of the device path protocol in case efi
has started.
Fixes: e55a4acb54e8 ("efi_loader: net: set EFI bootdevice device path to HTTP when
loaded from wget")
Signed-off-by: Adriano Cordova <adriano.cord...@canonical.com>
---
lib/efi_loader/efi_net.c | 53 +++++++++++++++++++++++++++++++++++-----
1 file changed, 47 insertions(+), 6 deletions(-)
diff --git a/lib/efi_loader/efi_net.c b/lib/efi_loader/efi_net.c
index 67593ef50c..1e87cd7be6 100644
--- a/lib/efi_loader/efi_net.c
+++ b/lib/efi_loader/efi_net.c
@@ -925,12 +925,15 @@ efi_status_t efi_net_register(void)
&netobj->net);
if (r != EFI_SUCCESS)
goto failure_to_add_protocol;
- if (!net_dp)
- efi_net_set_dp("Net", NULL);
- r = efi_add_protocol(&netobj->header, &efi_guid_device_path,
- net_dp);
+
+ if (net_dp)
+ r = efi_add_protocol(&netobj->header, &efi_guid_device_path,
+ net_dp);
+ else
+ r = efi_net_set_dp("Net", NULL);
if (r != EFI_SUCCESS)
goto failure_to_add_protocol;
+
r = efi_add_protocol(&netobj->header, &efi_pxe_base_code_protocol_guid,
&netobj->pxe);
if (r != EFI_SUCCESS)
@@ -1055,18 +1058,56 @@ out_of_resources:
*/
efi_status_t efi_net_set_dp(const char *dev, const char *server)
{
- efi_free_pool(net_dp);
+ efi_status_t ret;
+ struct efi_handler *phandler;
+ struct efi_device_path *old_net_dp;
+ old_net_dp = net_dp;
net_dp = NULL;
if (!strcmp(dev, "Net"))
net_dp = efi_dp_from_eth();
else if (!strcmp(dev, "Http"))
net_dp = efi_dp_from_http(server);
- if (!net_dp)
+ if (!net_dp) {
+ net_dp = old_net_dp;
return EFI_OUT_OF_RESOURCES;
+ }
+
+ if (!netobj)
+ return EFI_SUCCESS;
+
+ phandler = NULL;
+ efi_search_protocol(&netobj->header, &efi_guid_device_path, &phandler);
+
+ if (!phandler)
+ goto add;
+
+ if (phandler->protocol_interface != old_net_dp) {
+ ret = EFI_DEVICE_ERROR;
+ goto error;
+ }
This is not an error condition. Some other code may have changed the
device-path. We must not free what we haven't allocated. But we should
still try to replace it.
So can we have a logic like:
old_dp = net_dp;
new_dp = ...
OpenProtocol(handle, GUID, &old_dp, NULL, NULL,
EFI_OPEN_PROTOCOL_GET_PROTOCOL);
if (!efi_dp_match(old_dp, new_dp) {
FreePool(new_dp);
return EFI_SUCCESS;
}
ret = ReinstallProtocolInterface(handle, GUID, old_dp, new_dp);
if (ret == EFI_SUCCESS) {
FreePool(net_dp)
} else {
FreePool(new_dp);
}
return ret;
Best regards
Heinrich
+
+ ret = efi_reinstall_protocol_interface(&netobj->header,
&efi_guid_device_path,
+ old_net_dp, net_dp);
+ if (ret != EFI_SUCCESS)
Can net_dp be freed if an error occurred?
+ return ret;
+
+ efi_free_pool(old_net_dp);
return EFI_SUCCESS;
+add:
+ ret = efi_add_protocol(&netobj->header, &efi_guid_device_path,
+ net_dp);
+ if (ret == EFI_SUCCESS) {
+ efi_free_pool(old_net_dp);
+ return ret;
+ }
+error:
+ // Failed, restore
+ efi_free_pool(net_dp);
+ net_dp = old_net_dp;
+ return ret;
}
/**
