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Ian Abbott ec56b9f1c1 comedi: Fix getting range information for subdevices 16 to 255 
commit 10d28cffb3 upstream.

The `COMEDI_RANGEINFO` ioctl does not work properly for subdevice
indices above 15.  Currently, the only in-tree COMEDI drivers that
support more than 16 subdevices are the "8255" driver and the
"comedi_bond" driver.  Making the ioctl work for subdevice indices up to
255 is achievable.  It needs minor changes to the handling of the
`COMEDI_RANGEINFO` and `COMEDI_CHANINFO` ioctls that should be mostly
harmless to user-space, apart from making them less broken.  Details
follow...

The `COMEDI_RANGEINFO` ioctl command gets the list of supported ranges
(usually with units of volts or milliamps) for a COMEDI subdevice or
channel.  (Only some subdevices have per-channel range tables, indicated
by the `SDF_RANGETYPE` flag in the subdevice information.)  It uses a
`range_type` value and a user-space pointer, both supplied by
user-space, but the `range_type` value should match what was obtained
using the `COMEDI_CHANINFO` ioctl (if the subdevice has per-channel
range tables)  or `COMEDI_SUBDINFO` ioctl (if the subdevice uses a
single range table for all channels).  Bits 15 to 0 of the `range_type`
value contain the length of the range table, which is the only part that
user-space should care about (so it can use a suitably sized buffer to
fetch the range table).  Bits 23 to 16 store the channel index, which is
assumed to be no more than 255 if the subdevice has per-channel range
tables, and is set to 0 if the subdevice has a single range table.  For
`range_type` values produced by the `COMEDI_SUBDINFO` ioctl, bits 31 to
24 contain the subdevice index, which is assumed to be no more than 255.
But for `range_type` values produced by the `COMEDI_CHANINFO` ioctl,
bits 27 to 24 contain the subdevice index, which is assumed to be no
more than 15, and bits 31 to 28 contain the COMEDI device's minor device
number for some unknown reason lost in the mists of time.  The
`COMEDI_RANGEINFO` ioctl extract the length from bits 15 to 0 of the
user-supplied `range_type` value, extracts the channel index from bits
23 to 16 (only used if the subdevice has per-channel range tables),
extracts the subdevice index from bits 27 to 24, and ignores bits 31 to
28.  So for subdevice indices 16 to 255, the `COMEDI_SUBDINFO` or
`COMEDI_CHANINFO` ioctl will report a `range_type` value that doesn't
work with the `COMEDI_RANGEINFO` ioctl.  It will either get the range
table for the subdevice index modulo 16, or will fail with `-EINVAL`.

To fix this, always use bits 31 to 24 of the `range_type` value to hold
the subdevice index (assumed to be no more than 255).  This affects the
`COMEDI_CHANINFO` and `COMEDI_RANGEINFO` ioctls.  There should not be
anything in user-space that depends on the old, broken usage, although
it may now see different values in bits 31 to 28 of the `range_type`
values reported by the `COMEDI_CHANINFO` ioctl for subdevices that have
per-channel subdevices.  User-space should not be trying to decode bits
31 to 16 of the `range_type` values anyway.

Fixes: ed9eccbe89 ("Staging: add comedi core")
Cc: stable@vger.kernel.org #5.17+
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Link: https://patch.msgid.link/20251203162438.176841-1-abbotti@mev.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2026-01-30 10:32:15 +01:00
arch x86/kfence: avoid writing L1TF-vulnerable PTEs 2026-01-30 10:32:14 +01:00
block block: zero non-PI portion of auto integrity buffer 2026-01-23 11:21:16 +01:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: authencesn - reject too-short AAD (assoclen<8) to match ESP/ESN spec 2026-01-30 10:32:12 +01:00
Documentation fou: Don't allow 0 for FOU_ATTR_IPPROTO. 2026-01-30 10:32:12 +01:00
drivers comedi: Fix getting range information for subdevices 16 to 255 2026-01-30 10:32:15 +01:00
fs btrfs: fix missing fields in superblock backup with BLOCK_GROUP_TREE 2026-01-30 10:32:09 +01:00
include comedi: Fix getting range information for subdevices 16 to 255 2026-01-30 10:32:15 +01:00
init printk changes for 6.18 2025-10-04 11:13:11 -07:00
io_uring io_uring: move local task_work in exit cancel loop 2026-01-23 11:21:13 +01:00
ipc namespace-6.18-rc1 2025-09-29 11:20:29 -07:00
kernel hrtimer: Fix softirq base check in update_needs_ipi() 2026-01-23 11:21:28 +01:00
lib lib/buildid: use __kernel_read() for sleepable context 2026-01-23 11:21:25 +01:00
LICENSES LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2 2025-07-24 11:15:39 +02:00
mm slab: fix kmalloc_nolock() context check for PREEMPT_RT 2026-01-30 10:32:14 +01:00
net rxrpc: Fix recvmsg() unconditional requeue 2026-01-30 10:32:14 +01:00
rust rust: bitops: fix missing _find_* functions on 32-bit ARM 2026-01-23 11:21:12 +01:00
samples samples/ftrace: Adjust LoongArch register restore order in direct calls 2026-01-08 10:17:11 +01:00
scripts mcb: Add missing modpost build support 2026-01-08 10:16:47 +01:00
security landlock: Fix wrong type usage 2026-01-23 11:21:22 +01:00
sound ASoC: codecs: wsa881x: fix unnecessary initialisation 2026-01-23 11:21:28 +01:00
tools tools: ynl: Specify --no-line-number in ynl-regen.sh. 2026-01-30 10:32:12 +01:00
usr gen_init_cpio: Ignore fsync() returning EINVAL on pipes 2025-10-07 09:53:05 -07:00
virt KVM: Fix last_boosted_vcpu index assignment bug 2026-01-02 12:57:21 +01:00
.clang-format memblock: drop for_each_free_mem_pfn_range_in_zone_from() 2025-09-14 08:49:03 +03:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: remove Alyssa Rosenzweig 2025-09-18 21:17:31 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore .gitignore: ignore compile_commands.json globally 2025-08-12 15:53:55 -07:00
.mailmap 8 hotfixes. 4 are cc:stable, 7 are against mm/. 2025-11-26 12:38:05 -08:00
.pylintrc tools: docs: parse-headers.py: move it from sphinx dir 2025-08-29 15:54:42 -06:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: mark ISDN subsystem as orphan 2025-10-27 17:49:45 -07:00
Kbuild sched: Make migrate_{en,dis}able() inline 2025-09-25 09:57:16 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS soc: fixes for 6.18, part 4 2025-11-28 09:57:31 -08:00
Makefile Linux 6.18.7 2026-01-23 11:21:37 +01:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.