Messages in this thread Patch in this message | | | From | Kees Cook <> | Subject | [PATCH] firmware: coreboot: Check size of table entry and split memcpy | Date | Thu, 5 Jan 2023 20:53:31 -0800 |
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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(-)
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 */ -- 2.34.1
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