CVE-2025-39684
published 2025-09-05CVE-2025-39684: In the Linux kernel, the following vulnerability has been resolved: comedi: Fix use of uninitialized memory in do_insn_ioctl() and do_insnlist_ioctl() syzbot…
medium5.5CVSS 3.1
AVLACLPRLUINSUCNINAH
In the Linux kernel, the following vulnerability has been resolved:
comedi: Fix use of uninitialized memory in do_insn_ioctl() and do_insnlist_ioctl()
syzbot reports a KMSAN kernel-infoleak in `do_insn_ioctl()`. A kernel
buffer is allocated to hold `insn->n` samples (each of which is an
`unsigned int`). For some instruction types, `insn->n` samples are
copied back to user-space, unless an error code is being returned. The
problem is that not all the instruction handlers that need to return
data to userspace fill in the whole `insn->n` samples, so that there is
an information leak. There is a similar syzbot report for
`do_insnlist_ioctl()`, although it does not have a reproducer for it at
the time of writing.
One culprit is `insn_rw_emulate_bits()` which is used as the handler for
`INSN_READ` or `INSN_WRITE` instructions for subdevices that do not have
a specific handler for that instruction, but do have an `INSN_BITS`
handler. For `INSN_READ` it only fills in at most 1 sample, so if
`insn->n` is greater than 1, the remaining `insn->n - 1` samples copied
to userspace will be uninitialized kernel data.
Another culprit is `vm80xx_ai_insn_read()` in the "vm80xx" driver. It
never returns an error, even if it fails to fill the buffer.
Fix it in `do_insn_ioctl()` and `do_insnlist_ioctl()` by making sure
that uninitialized parts of the allocated buffer are zeroed before
handling each instruction.
Thanks to Arnaud Lecomte for their fix to `do_insn_ioctl()`. That fix
replaced the call to `kmalloc_array()` with `kcalloc()`, but it is not
always necessary to clear the whole buffer.
Affected
33 ranges· showing 25
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| debian | debian_linux | — | — |
| debian | linux | < linux 6.1.153-1 (bookworm) | linux 6.1.153-1 (bookworm) |
| debian | linux-6.1 | < linux 6.1.153-1 (bookworm) | linux 6.1.153-1 (bookworm) |
| linux | linux | — | — |
| linux | linux | >= ed9eccbe8970f6eedc1b978c157caf1251a896d4 < 868a1b68dcd9f2805bb86aa64862402f785d8c4a | 868a1b68dcd9f2805bb86aa64862402f785d8c4a |
| linux | linux | >= ed9eccbe8970f6eedc1b978c157caf1251a896d4 < ff4a7c18799c7fe999fa56c5cf276e13866b8c1a | ff4a7c18799c7fe999fa56c5cf276e13866b8c1a |
| linux | linux | >= ed9eccbe8970f6eedc1b978c157caf1251a896d4 < d84f6e77ebe3359394df32ecd97e0d76a25283dc | d84f6e77ebe3359394df32ecd97e0d76a25283dc |
| linux | linux | >= ed9eccbe8970f6eedc1b978c157caf1251a896d4 < f3b0c9ec54736f3b8118f93a473d22e11ee65743 | f3b0c9ec54736f3b8118f93a473d22e11ee65743 |
| linux | linux | >= ed9eccbe8970f6eedc1b978c157caf1251a896d4 < aecf0d557ddd95ce68193a5ee1dc4c87415ff08a | aecf0d557ddd95ce68193a5ee1dc4c87415ff08a |
| linux | linux | >= ed9eccbe8970f6eedc1b978c157caf1251a896d4 < 3cd212e895ca2d58963fdc6422502b10dd3966bb | 3cd212e895ca2d58963fdc6422502b10dd3966bb |
| linux | linux_kernel | — | — |
| linux | linux_kernel | >= 0 < 6.1.153-1 | 6.1.153-1 |
| linux | linux_kernel | >= 0 < 6.12.48-1 | 6.12.48-1 |
| linux | linux_kernel | >= 0 < 6.16.5-1 | 6.16.5-1 |
| linux | linux_kernel | >= 0 < 5.15.0-163.173 | 5.15.0-163.173 |
| linux | linux_kernel | >= 0 < 6.8.0-100.100 | 6.8.0-100.100 |
| linux | linux_kernel | >= 2.6.29 < 5.15.190 | 5.15.190 |
| linux | linux_kernel | >= 5.16 < 6.1.149 | 6.1.149 |
| linux | linux_kernel | >= 6.13 < 6.16.4 | 6.16.4 |
| linux | linux_kernel | >= 6.2 < 6.6.103 | 6.6.103 |
| linux | linux_kernel | >= 6.7 < 6.12.44 | 6.12.44 |
| msrc | azl3_kernel_6.6.96.2-1_on_azure_linux_3.0 | — | — |
| msrc | azl3_kernel_6.6.96.2-2_on_azure_linux_3.0 | — | — |
| msrc | cbl2_kernel_5.15.186.1-1_on_cbl_mariner_2.0 | — | — |
| ubuntu | linux-aws | — | — |
CVSS provenance
nvdv3.15.5MEDIUMCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
osv5.5MEDIUM