Commit 3b293487 authored by Kees Cook's avatar Kees Cook
Browse files

firmware: coreboot: Check size of table entry and use flex-array 



The memcpy() of the data following a coreboot_table_entry couldn't
be evaluated by the compiler under CONFIG_FORTIFY_SOURCE. To make it
easier to reason about, add an explicit flexible array member to struct
coreboot_device so the entire entry can be copied at once. Additionally,
validate the sizes before copying. Avoids this run-time false positive
warning:

  memcpy: detected field-spanning write (size 168) of single field "&device->entry" at drivers/firmware/google/coreboot_table.c:103 (size 8)

Reported-by: default avatarPaul Menzel <pmenzel@molgen.mpg.de>
Link: https://lore.kernel.org/all/03ae2704-8c30-f9f0-215b-7cdf4ad35a9a@molgen.mpg.de/


Cc: Jack Rosenthal <jrosenth@chromium.org>
Cc: Guenter Roeck <groeck@chromium.org>
Cc: Julius Werner <jwerner@chromium.org>
Cc: Brian Norris <briannorris@chromium.org>
Cc: Stephen Boyd <swboyd@chromium.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Reviewed-by: default avatarJulius Werner <jwerner@chromium.org>
Reviewed-by: default avatarGuenter Roeck <groeck@chromium.org>
Link: https://lore.kernel.org/r/20230107031406.gonna.761-kees@kernel.org


Reviewed-by: default avatarStephen Boyd <swboyd@chromium.org>
Reviewed-by: default avatarJack Rosenthal <jrosenth@chromium.org>
Link: https://lore.kernel.org/r/20230112230312.give.446-kees@kernel.org
parent 88603b6d

drivers/firmware/google/coreboot_table.c

+7 −2
Original line number Diff line number Diff line
@@ -93,14 +93,19 @@ static int coreboot_table_populate(struct device *dev, void *ptr) 
	for (i = 0; i < header->table_entries; i++) {

		entry = ptr_entry;



		device = kzalloc(sizeof(struct device) + entry->size, GFP_KERNEL);

		if (entry->size < sizeof(*entry)) {

			dev_warn(dev, "coreboot table entry too small!\n");

			return -EINVAL;

		}



		device = kzalloc(sizeof(device->dev) + entry->size, GFP_KERNEL);

		if (!device)

			return -ENOMEM;



		device->dev.parent = dev;

		device->dev.bus = &coreboot_bus_type;

		device->dev.release = coreboot_device_release;

		memcpy(&device->entry, ptr_entry, entry->size);

		memcpy(device->raw, ptr_entry, entry->size);



		switch (device->entry.tag) {

		case LB_TAG_CBMEM_ENTRY:

drivers/firmware/google/coreboot_table.h

+1 −0
Original line number Diff line number Diff line
@@ -79,6 +79,7 @@ struct coreboot_device { 
		struct lb_cbmem_ref cbmem_ref;

		struct lb_cbmem_entry cbmem_entry;

		struct lb_framebuffer framebuffer;

		DECLARE_FLEX_ARRAY(u8, raw);

	};

};