On Mon, Mar 20, 2023 at 1:09 PM Benjamin Gray <bgray@xxxxxxxxxxxxx> wrote:
>
> Similar to commit 4c9d410f32b3 ("initramfs: Check timestamp to prevent
> broken cpio archive"), except asserts that the timestamp is
> non-negative. This can happen when the KBUILD_BUILD_TIMESTAMP is a value
> before UNIX epoch, which may be set when making reproducible builds that
> don't want to look like they use a valid date.
>
> While support for dates before 1970 might not be supported, this is more
> about preventing undetected CPIO corruption. The printf's use a minimum
> length format specifier, and will happily make the field longer than 8
> characters if they need to.
>
> Signed-off-by: Benjamin Gray <bgray@xxxxxxxxxxxxx>
>
> ---
Applied to linux-kbuild. (only 1/2)
Thanks.
>
> Ran into this when setting KBUILD_BUILD_TIMESTAMP=0000-01-01. The kernel
> builds and boots to an initramfs just fine, but inexplicably failed to
> load any root disks. It was a pain to debug, because the first sign of
> an issue was so deep into the boot sequence.
> ---
> usr/gen_init_cpio.c | 12 +++++++++---
> 1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/usr/gen_init_cpio.c b/usr/gen_init_cpio.c
> index ee01e40e8bc6..61230532fef1 100644
> --- a/usr/gen_init_cpio.c
> +++ b/usr/gen_init_cpio.c
> @@ -353,6 +353,12 @@ static int cpio_mkfile(const char *name, const char *location,
> buf.st_mtime = 0xffffffff;
> }
>
> + if (buf.st_mtime < 0) {
> + fprintf(stderr, "%s: Timestamp negative, clipping.\n",
> + location);
> + buf.st_mtime = 0;
> + }
> +
> if (buf.st_size > 0xffffffff) {
> fprintf(stderr, "%s: Size exceeds maximum cpio file size\n",
> location);
> @@ -602,10 +608,10 @@ int main (int argc, char *argv[])
> /*
> * Timestamps after 2106-02-07 06:28:15 UTC have an ascii hex time_t
> * representation that exceeds 8 chars and breaks the cpio header
> - * specification.
> + * specification. Negative timestamps similarly exceed 8 chars.
> */
> - if (default_mtime > 0xffffffff) {
> - fprintf(stderr, "ERROR: Timestamp too large for cpio format\n");
> + if (default_mtime > 0xffffffff || default_mtime < 0) {
> + fprintf(stderr, "ERROR: Timestamp out of range for cpio format\n");
> exit(1);
> }
>
>
> base-commit: 065ffaee73892e8a3629b4cfbe635697807a3c6f
> --
> 2.39.2
>
--
Best Regards
Masahiro Yamada
