CVE-2025-38478comedi: Fix initialization of data for instructions that write to subdevice

Official description

In the Linux kernel, the following vulnerability has been resolved: comedi: Fix initialization of data for instructions that write to subdevice Some Comedi subdevice instruction handlers are known to access instruction data elements beyond the first `insn->n` elements in some cases. The `do_insn_ioctl()` and `do_insnlist_ioctl()` functions allocate at least `MIN_SAMPLES` (16) data elements to deal with this, but they do not initialize all of that. For Comedi instruction codes that write to the subdevice, the first `insn->n` data elements are copied from user-space, but the remaining elements are left uninitialized. That could be a problem if the subdevice instruction handler reads the uninitialized data. Ensure that the first `MIN_SAMPLES` elements are initialized before calling these instruction handlers, filling the uncopied elements with 0. For `do_insnlist_ioctl()`, the same data buffer elements are used for handling a list of instructions, so ensure the first `MIN_SAMPLES` elements are initialized for each instruction that writes to the subdevice.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/6f38c6380c3b38a05032b8881e41137385a6ce02
• https://git.kernel.org/stable/c/13e4d9038a1e869445a996a3f604a84ef52fe8f4
• https://git.kernel.org/stable/c/020eed5681d0f9bced73970368078a92d6cfaa9c
• https://git.kernel.org/stable/c/d3436638738ace8f101af7bdee2eae1bc38e9b29
• https://git.kernel.org/stable/c/673ee92bd2d31055bca98a1d96b653f5284289c4
• https://git.kernel.org/stable/c/c42116dc70af6664526f7aa82cf937824ab42649
• https://git.kernel.org/stable/c/fe8713fb4e4e82a4f91910d9a41bf0613e69a0b9
• https://git.kernel.org/stable/c/46d8c744136ce2454aa4c35c138cc06817f92b8e
• https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html
• https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html