On Wed, Mar 09, 2022 at 10:50:32AM -0800, Kees Cook wrote:
> As done with other image addresses in other architectures, use an
> explicit flexible array instead of "address of char", which can trip
> bounds checking done by the compiler. Found when building with
> -Warray-bounds:
>
> In file included from ./include/linux/byteorder/little_endian.h:5,
> from ./arch/mips/include/uapi/asm/byteorder.h:15,
> from ./arch/mips/include/asm/bitops.h:21,
> from ./include/linux/bitops.h:33,
> from ./include/linux/kernel.h:22,
> from arch/mips/boot/compressed/decompress.c:13:
> arch/mips/boot/compressed/decompress.c: In function 'decompress_kernel':
> ./include/asm-generic/unaligned.h:14:8: warning: array subscript -1 is outside array bounds of 'unsigned char[1]' [-Warray-bounds]
> 14 | __pptr->x; \
> | ~~~~~~^~~
> ./include/uapi/linux/byteorder/little_endian.h:35:51: note: in definition of macro '__le32_to_cpu'
> 35 | #define __le32_to_cpu(x) ((__force __u32)(__le32)(x))
> | ^
> ./include/asm-generic/unaligned.h:32:21: note: in expansion of macro '__get_unaligned_t'
> 32 | return le32_to_cpu(__get_unaligned_t(__le32, p));
> | ^~~~~~~~~~~~~~~~~
> arch/mips/boot/compressed/decompress.c:29:37: note: while referencing '__image_end'
> 29 | extern unsigned char __image_begin, __image_end;
> | ^~~~~~~~~~~
>
> Cc: Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx>
> Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
> Cc: linux-mips@xxxxxxxxxxxxxxx
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Reviewed-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
Thanks
--
Gustavo
> ---
> arch/mips/boot/compressed/decompress.c | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/arch/mips/boot/compressed/decompress.c b/arch/mips/boot/compressed/decompress.c
> index aae1346a509a..5b38a802e101 100644
> --- a/arch/mips/boot/compressed/decompress.c
> +++ b/arch/mips/boot/compressed/decompress.c
> @@ -26,7 +26,7 @@ unsigned long free_mem_ptr;
> unsigned long free_mem_end_ptr;
>
> /* The linker tells us where the image is. */
> -extern unsigned char __image_begin, __image_end;
> +extern unsigned char __image_begin[], __image_end[];
>
> /* debug interfaces */
> #ifdef CONFIG_DEBUG_ZBOOT
> @@ -91,9 +91,9 @@ void decompress_kernel(unsigned long boot_heap_start)
> {
> unsigned long zimage_start, zimage_size;
>
> - zimage_start = (unsigned long)(&__image_begin);
> - zimage_size = (unsigned long)(&__image_end) -
> - (unsigned long)(&__image_begin);
> + zimage_start = (unsigned long)(__image_begin);
> + zimage_size = (unsigned long)(__image_end) -
> + (unsigned long)(__image_begin);
>
> puts("zimage at: ");
> puthex(zimage_start);
> @@ -121,7 +121,7 @@ void decompress_kernel(unsigned long boot_heap_start)
> dtb_size = fdt_totalsize((void *)&__appended_dtb);
>
> /* last four bytes is always image size in little endian */
> - image_size = get_unaligned_le32((void *)&__image_end - 4);
> + image_size = get_unaligned_le32((void *)__image_end - 4);
>
> /* The device tree's address must be properly aligned */
> image_size = ALIGN(image_size, STRUCT_ALIGNMENT);
> --
> 2.32.0
>
