Messages in this thread | | | Subject | Re: [PATCH v5 2/5] efi: Add embedded peripheral firmware support | From | Hans de Goede <> | Date | Tue, 1 May 2018 21:11:25 +0200 |
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Hi,
On 01-05-18 16:36, Mimi Zohar wrote: > [Cc'ing linux-security] > > On Sun, 2018-04-29 at 11:35 +0200, Hans de Goede wrote: > [...] >> diff --git a/drivers/base/firmware_loader/fallback_efi.c b/drivers/base/firmware_loader/fallback_efi.c >> new file mode 100644 >> index 000000000000..82ba82f48a79 >> --- /dev/null >> +++ b/drivers/base/firmware_loader/fallback_efi.c >> @@ -0,0 +1,51 @@ >> +// SPDX-License-Identifier: GPL-2.0 >> + >> +#include <linux/efi_embedded_fw.h> >> +#include <linux/property.h> >> +#include <linux/security.h> >> +#include <linux/vmalloc.h> >> + >> +#include "fallback.h" >> +#include "firmware.h" >> + >> +int fw_get_efi_embedded_fw(struct device *dev, struct fw_priv *fw_priv, >> + enum fw_opt *opt_flags, int ret) >> +{ >> + enum kernel_read_file_id id = READING_FIRMWARE; > > Please define a new kernel_read_file_id for this (eg. > READING_FIRMWARE_EFI_EMBEDDED).
Are you sure, I wonder how useful it is to add a new kernel_read_file_id every time a new way to get firmware comes up?
I especially wonder about the sense in adding a new id given that the quite old FIRMWARE_PREALLOC_BUFFER is still not supported / checked properly by the security code.
Anyways I can add a new id if you want me to, what about when fw_get_efi_embedded_fw is reading into a driver allocated buffer, do you want a separate EADING_FIRMWARE_EFI_EMBEDDED_PREALLOC_BUFFER for that ?
> >> + size_t size, max = INT_MAX; >> + int rc; >> + >> + if (!dev) >> + return ret; >> + >> + if (!device_property_read_bool(dev, "efi-embedded-firmware")) >> + return ret; > > Instead of calling security_kernel_post_read_file(), either in > device_property_read_bool() or here call security_kernel_read_file(). > > The pre read call is for deciding whether to allow this call > independent of the firmware being loaded, whereas the post security > call is currently being used by IMA-appraisal for verifying a > signature. There might be other LSMs using the post hook as well. As > there is no kernel signature associated with this firmware, use the > security pre read_file hook.
Only the pre hook? I believe the post-hook should still be called too, right? So that we've hashes of all loaded firmwares in the IMA core.
Regards,
Hans
> > thanks, > > Mimi > >> + >> + *opt_flags |= FW_OPT_NO_WARN | FW_OPT_NOCACHE | FW_OPT_NOFALLBACK; >> + >> + /* Already populated data member means we're loading into a buffer */ >> + if (fw_priv->data) { >> + id = READING_FIRMWARE_PREALLOC_BUFFER; >> + max = fw_priv->allocated_size; >> + } >> + >> + rc = efi_get_embedded_fw(fw_priv->fw_name, &fw_priv->data, &size, max); >> + if (rc) { >> + dev_warn(dev, "Firmware %s not in EFI\n", fw_priv->fw_name); >> + return ret; >> + } >> + >> + rc = security_kernel_post_read_file(NULL, fw_priv->data, size, id); >> + if (rc) { >> + if (id != READING_FIRMWARE_PREALLOC_BUFFER) { >> + vfree(fw_priv->data); >> + fw_priv->data = NULL; >> + } >> + return rc; >> + } >> + >> + dev_dbg(dev, "using efi-embedded fw %s\n", fw_priv->fw_name); >> + fw_priv->size = size; >> + fw_state_done(fw_priv); >> + return 0; >> +} >
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