Messages in this thread | | | From | Guenter Roeck <> | Date | Fri, 6 Jan 2023 20:39:06 -0800 | Subject | Re: [PATCH v2] firmware: coreboot: Check size of table entry and split memcpy |
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On Fri, Jan 6, 2023 at 7:14 PM Kees Cook <keescook@chromium.org> wrote: > > 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: Guenter Roeck <groeck@chromium.org>
> --- > v2: move flex array to struct coreboot_device (julius) > v1: https://lore.kernel.org/lkml/20230106045327.never.413-kees@kernel.org > --- > drivers/firmware/google/coreboot_table.c | 9 +++++++-- > drivers/firmware/google/coreboot_table.h | 1 + > 2 files changed, 8 insertions(+), 2 deletions(-) > > diff --git a/drivers/firmware/google/coreboot_table.c b/drivers/firmware/google/coreboot_table.c > index 2652c396c423..564a3c908838 100644 > --- a/drivers/firmware/google/coreboot_table.c > +++ b/drivers/firmware/google/coreboot_table.c > @@ -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, entry, entry->size); > > switch (device->entry.tag) { > case LB_TAG_CBMEM_ENTRY: > diff --git a/drivers/firmware/google/coreboot_table.h b/drivers/firmware/google/coreboot_table.h > index 37f4d335a606..d814dca33a08 100644 > --- a/drivers/firmware/google/coreboot_table.h > +++ b/drivers/firmware/google/coreboot_table.h > @@ -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); > }; > }; > > -- > 2.34.1 >
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