On Thu, 10 Sep 2026 02:09:01 +0000
[email protected] wrote:
> Thank you for your contribution! Sashiko AI review found 2 potential issue(s)
> to consider:
> - [Medium] Mismatched boundary checks for XBC_DATA_MAX cause inconsistent
> fallback behavior for embedded bootconfigs.
> - [Low] Misleading error message when bootconfig size exceeds XBC_DATA_MAX.
> --
>
> commit a24325c6fe0374f1cfc3fc8cbe63efbad0f22f32
> Author: Masami Hiramatsu (Google) <[email protected]>
>
> bootconfig: Fix integer overflow in initrd size check
>
> This commit fixes an integer overflow where a crafted initrd with a huge
> bootconfig size can cause pointer arithmetic wrap-around. It ensures the
> initrd bounds are respected and verifies the size does not exceed max limits.
>
> Closes:
> https://lore.kernel.org/all/[email protected]/
>
> > diff --git a/init/main.c b/init/main.c
> > index a9362b2cc258a..de24c41ce815e 100644
> > --- a/init/main.c
> > +++ b/init/main.c
>
> [ ... ]
>
> > @@ -294,16 +295,21 @@ static void * __init
> > get_boot_config_from_initrd(size_t *_size)
> >
> > found:
> > hdr = (u8 *)(data - 8);
> > + if ((unsigned long)hdr < initrd_start)
> > + return NULL;
> > +
> > size = get_unaligned_le32(hdr);
> > csum = get_unaligned_le32(hdr + 4);
> >
> > - data = ((void *)hdr) - size;
> > - if ((unsigned long)data < initrd_start) {
> > - pr_err("bootconfig size %d is greater than initrd size %ld\n",
> > + if (size > XBC_DATA_MAX ||
>
> [Severity: Medium]
> If the size is exactly equal to XBC_DATA_MAX, this check passes and the
> function returns a valid data pointer. This prevents the caller from falling
> back to the embedded bootconfig:
>
> init/main.c:setup_boot_config() {
> ...
> data = get_boot_config_from_initrd(&size);
> if (!data) {
> data = xbc_get_embedded_bootconfig(&size);
> ...
> }
> ...
> }
>
> However, setup_boot_config() uses inclusive inequality for XBC_DATA_MAX:
>
> init/main.c:setup_boot_config() {
> ...
> if (size >= XBC_DATA_MAX) {
> pr_err("bootconfig size %ld greater than max size %d\n", ...);
> return;
> }
> ...
> }
Hmm, this is wrong. Since XBC_DATA_MAX is including maximum size,
setup_boot_config() should change this condition.
>
> Because the limits don't match, an exact size of XBC_DATA_MAX causes
> setup_boot_config() to reject the payload and abort without attempting
> the fallback. Should this check use size >= XBC_DATA_MAX to match?
>
> > + size > ((unsigned long)hdr - initrd_start)) {
> > + pr_err("bootconfig size %u is greater than initrd size %lu\n",
> > + size, initrd_end - initrd_start);
>
> [Severity: Low]
> If this error path is taken specifically because size > XBC_DATA_MAX, the
> error message claims the bootconfig size is greater than the initrd size.
> Can this message be updated to accurately reflect which limit was exceeded?
Ah, good catch :)
Thanks,
>
> > return NULL;
> > }
> >
> > + data = ((void *)hdr) - size;
> > +
> > if (xbc_calc_checksum(data, size) != csum) {
> > pr_err("bootconfig checksum failed\n");
> > return NULL;
>
> --
> Sashiko AI review ยท
> https://sashiko.dev/#/patchset/178900555453.200943.4719889510443114485.stgit@devnote2?part=2
--
Masami Hiramatsu (Google) <[email protected]>
