Message ID | 20230106045327.never.413-kees@kernel.org (mailing list archive) |
---|---|
State | Superseded |
Headers | show |
Series | firmware: coreboot: Check size of table entry and split memcpy | expand |
Have you considered adding the flexible array member directly to the union in struct coreboot_device instead? I think that would make this a bit simpler by not having to copy header and data portion separately.
On Fri, Jan 06, 2023 at 04:03:35PM +0100, Julius Werner wrote: > Have you considered adding the flexible array member directly to the > union in struct coreboot_device instead? I think that would make this > a bit simpler by not having to copy header and data portion > separately. Are you thinking something like this? 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); }; };
Yeah, exactly. Isn't that a bit simpler? (I wasn't aware of the flexible array member in union issue, but it sounds like we have a neat solution for that already.) On Fri, Jan 6, 2023 at 9:35 PM Kees Cook <keescook@chromium.org> wrote: > > On Fri, Jan 06, 2023 at 04:03:35PM +0100, Julius Werner wrote: > > Have you considered adding the flexible array member directly to the > > union in struct coreboot_device instead? I think that would make this > > a bit simpler by not having to copy header and data portion > > separately. > > Are you thinking something like this? > > > 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); > }; > }; > > > -- > Kees Cook
diff --git a/drivers/firmware/google/coreboot_table.c b/drivers/firmware/google/coreboot_table.c index 2652c396c423..102edfb4eb7b 100644 --- a/drivers/firmware/google/coreboot_table.c +++ b/drivers/firmware/google/coreboot_table.c @@ -93,6 +93,11 @@ static int coreboot_table_populate(struct device *dev, void *ptr) for (i = 0; i < header->table_entries; i++) { entry = ptr_entry; + if (entry->size < sizeof(*entry)) { + dev_warn(dev, "coreboot table entry too small!\n"); + return -EINVAL; + } + device = kzalloc(sizeof(struct device) + entry->size, GFP_KERNEL); if (!device) return -ENOMEM; @@ -100,7 +105,8 @@ static int coreboot_table_populate(struct device *dev, void *ptr) device->dev.parent = dev; device->dev.bus = &coreboot_bus_type; device->dev.release = coreboot_device_release; - memcpy(&device->entry, ptr_entry, entry->size); + device->entry = *entry; + memcpy(device->entry.data, entry->data, entry->size - sizeof(*entry)); 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..2a2cea79204b 100644 --- a/drivers/firmware/google/coreboot_table.h +++ b/drivers/firmware/google/coreboot_table.h @@ -29,6 +29,7 @@ struct coreboot_table_header { struct coreboot_table_entry { u32 tag; u32 size; + u8 data[]; /* Size here is: "size - (sizeof(u32) * 2)" */ }; /* Points to a CBMEM entry */
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_table_entry, and 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> --- drivers/firmware/google/coreboot_table.c | 8 +++++++- drivers/firmware/google/coreboot_table.h | 1 + 2 files changed, 8 insertions(+), 1 deletion(-)