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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: Paul 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: Kees Cook <keescook@chromium.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Link: https://lore.kernel.org/r/20230107031406.gonna.761-kees@kernel.org
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Jack Rosenthal <jrosenth@chromium.org>
Link: https://lore.kernel.org/r/20230112230312.give.446-kees@kernel.org
This commit is contained in:
Kees Cook 2023-01-12 15:03:16 -08:00
parent 88603b6dc4
commit 3b293487b8
2 changed files with 8 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
drivers/firmware/google/coreboot_table.c
View File

@ -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:

1
drivers/firmware/google/coreboot_table.h
View File

@ -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);
};
};