Entreprise française de cybersécurité depuis 2004
☎ 03 60 47 09 81 - info@securiteinfo.com
☎ 03 60 47 09 81 - info@securiteinfo.com
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 kernelbuffer is allocated to hold `insn->n` samples (each of which is an`unsigned int`). For some instruction types, `insn->n` samples arecopied back to user-space, unless an error code is being returned. Theproblem is that not all the instruction handlers that need to returndata to userspace fill in the whole `insn->n` samples, so that there isan information leak. There is a similar syzbot report for`do_insnlist_ioctl()`, although it does not have a reproducer for it atthe 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 havea 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 copiedto userspace will be uninitialized kernel data.Another culprit is `vm80xx_ai_insn_read()` in the "vm80xx" driver. Itnever returns an error, even if it fails to fill the buffer.Fix it in `do_insn_ioctl()` and `do_insnlist_ioctl()` by making surethat uninitialized parts of the allocated buffer are zeroed beforehandling each instruction.Thanks to Arnaud Lecomte for their fix to `do_insn_ioctl()`. That fixreplaced the call to `kmalloc_array()` with `kcalloc()`, but it is notalways necessary to clear the whole buffer.
No PoCs from references.
- https://github.com/w4zu/Debian_security