linux.git/drivers/char/misc.c, branch v6.12.80 Clone of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git char: misc: restrict the dynamic range to exclude reserved minors 2025-11-13T20:34:32+00:00 Thadeu Lima de Souza Cascardo cascardo@igalia.com 2025-04-23T08:45:42+00:00 c5f456784a8478f43afabd2d73227cd92012a0e5 [ Upstream commit 31b636d2c41613e3bd36256a4bd53e9dacfa2677 ] When this was first reported [1], the possibility of having sufficient number of dynamic misc devices was theoretical, in the case of dlm driver. In practice, its userspace never created more than one device. What we know from commit ab760791c0cf ("char: misc: Increase the maximum number of dynamic misc devices to 1048448"), is that the miscdevice interface has been used for allocating more than the single-shot devices it was designed for. And it is not only coresight_tmc, but many other drivers are able to create multiple devices. On systems like the ones described in the above commit, it is certain that the dynamic allocation will allocate certain reserved minor numbers, leading to failures when a later driver tries to claim its reserved number. Instead of excluding the historically statically allocated range from dynamic allocation, restrict the latter to minors above 255. That also removes the need for DYNAMIC_MINORS and the convolution in allocating minor numbers, simplifying the code. Since commit ab760791c0cf ("char: misc: Increase the maximum number of dynamic misc devices to 1048448") has been applied, such range is already possible. And given such devices already need to be dynamically created, there should be no systems where this might become a problem. [1] https://lore.kernel.org/all/1257813017-28598-3-git-send-email-cascardo@holoscopio.com/ Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com> Link: https://lore.kernel.org/r/20250423-misc-dynrange-v4-1-133b5ae4ca18@igalia.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 31b636d2c41613e3bd36256a4bd53e9dacfa2677 ]

When this was first reported [1], the possibility of having sufficient
number of dynamic misc devices was theoretical, in the case of dlm driver.
In practice, its userspace never created more than one device.

What we know from commit ab760791c0cf ("char: misc: Increase the maximum
number of dynamic misc devices to 1048448"), is that the miscdevice
interface has been used for allocating more than the single-shot devices it
was designed for. And it is not only coresight_tmc, but many other drivers
are able to create multiple devices.

On systems like the ones described in the above commit, it is certain that
the dynamic allocation will allocate certain reserved minor numbers,
leading to failures when a later driver tries to claim its reserved number.

Instead of excluding the historically statically allocated range from
dynamic allocation, restrict the latter to minors above 255. That also
removes the need for DYNAMIC_MINORS and the convolution in allocating minor
numbers, simplifying the code.

Since commit ab760791c0cf ("char: misc: Increase the maximum number of
dynamic misc devices to 1048448") has been applied, such range is already
possible. And given such devices already need to be dynamically created,
there should be no systems where this might become a problem.

[1] https://lore.kernel.org/all/1257813017-28598-3-git-send-email-cascardo@holoscopio.com/

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
Link: https://lore.kernel.org/r/20250423-misc-dynrange-v4-1-133b5ae4ca18@igalia.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
char: Use list_del_init() in misc_deregister() to reinitialize list pointer 2025-11-13T20:34:20+00:00 Xion Wang xion.wang@mediatek.com 2025-09-04T06:37:04+00:00 e9f66c989de4976ed29fcb32b6045bcdba07d396 [ Upstream commit e28022873c0d051e980c4145f1965cab5504b498 ] Currently, misc_deregister() uses list_del() to remove the device from the list. After list_del(), the list pointers are set to LIST_POISON1 and LIST_POISON2, which may help catch use-after-free bugs, but does not reset the list head. If misc_deregister() is called more than once on the same device, list_empty() will not return true, and list_del() may be called again, leading to undefined behavior. Replace list_del() with list_del_init() to reinitialize the list head after deletion. This makes the code more robust against double deregistration and allows safe usage of list_empty() on the miscdevice after deregistration. [ Note, this seems to keep broken out-of-tree drivers from doing foolish things. While this does not matter for any in-kernel drivers, external drivers could use a bit of help to show them they shouldn't be doing stuff like re-registering misc devices - gregkh ] Signed-off-by: Xion Wang <xion.wang@mediatek.com> Link: https://lore.kernel.org/r/20250904063714.28925-2-xion.wang@mediatek.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit e28022873c0d051e980c4145f1965cab5504b498 ]

Currently, misc_deregister() uses list_del() to remove the device
from the list. After list_del(), the list pointers are set to
LIST_POISON1 and LIST_POISON2, which may help catch use-after-free bugs,
but does not reset the list head.
If misc_deregister() is called more than once on the same device,
list_empty() will not return true, and list_del() may be called again,
leading to undefined behavior.

Replace list_del() with list_del_init() to reinitialize the list head
after deletion. This makes the code more robust against double
deregistration and allows safe usage of list_empty() on the miscdevice
after deregistration.

[ Note, this seems to keep broken out-of-tree drivers from doing foolish
  things.  While this does not matter for any in-kernel drivers,
  external drivers could use a bit of help to show them they shouldn't
  be doing stuff like re-registering misc devices - gregkh ]

Signed-off-by: Xion Wang <xion.wang@mediatek.com>
Link: https://lore.kernel.org/r/20250904063714.28925-2-xion.wang@mediatek.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
char: misc: Does not request module for miscdevice with dynamic minor 2025-11-13T20:34:14+00:00 Zijun Hu zijun.hu@oss.qualcomm.com 2025-07-14T15:34:17+00:00 6f3dcc809071deb8f7f07954d597b418cf62d3af [ Upstream commit 1ba0fb42aa6a5f072b1b8c0b0520b32ad4ef4b45 ] misc_open() may request module for miscdevice with dynamic minor, which is meaningless since: - The dynamic minor allocated is unknown in advance without registering miscdevice firstly. - Macro MODULE_ALIAS_MISCDEV() is not applicable for dynamic minor. Fix by only requesting module for miscdevice with fixed minor. Acked-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com> Signed-off-by: Zijun Hu <zijun.hu@oss.qualcomm.com> Link: https://lore.kernel.org/r/20250714-rfc_miscdev-v6-6-2ed949665bde@oss.qualcomm.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 1ba0fb42aa6a5f072b1b8c0b0520b32ad4ef4b45 ]

misc_open() may request module for miscdevice with dynamic minor, which
is meaningless since:

- The dynamic minor allocated is unknown in advance without registering
  miscdevice firstly.
- Macro MODULE_ALIAS_MISCDEV() is not applicable for dynamic minor.

Fix by only requesting module for miscdevice with fixed minor.

Acked-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
Signed-off-by: Zijun Hu <zijun.hu@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20250714-rfc_miscdev-v6-6-2ed949665bde@oss.qualcomm.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
char: misc: Make misc_register() reentry for miscdevice who wants dynamic minor 2025-11-13T20:34:14+00:00 Zijun Hu zijun.hu@oss.qualcomm.com 2025-07-14T15:34:16+00:00 72cd71ec60e89b4d9662578d46c5302d09957247 [ Upstream commit 52e2bb5ff089d65e2c7d982fe2826dc88e473d50 ] For miscdevice who wants dynamic minor, it may fail to be registered again without reinitialization after being de-registered, which is illustrated by kunit test case miscdev_test_dynamic_reentry() newly added. There is a real case found by cascardo when a part of minor range were contained by range [0, 255): 1) wmi/dell-smbios registered minor 122, and acpi_thermal_rel registered minor 123 2) unbind "int3400 thermal" driver from its device, this will de-register acpi_thermal_rel 3) rmmod then insmod dell_smbios again, now wmi/dell-smbios is using minor 123 4) bind the device to "int3400 thermal" driver again, acpi_thermal_rel fails to register. Some drivers may reuse the miscdevice structure after they are deregistered If the intention is to allocate a dynamic minor, if the minor number is not reset to MISC_DYNAMIC_MINOR before calling misc_register(), it will try to register a previously dynamically allocated minor number, which may have been registered by a different driver. One such case is the acpi_thermal_rel misc device, registered by the int3400 thermal driver. If the device is unbound from the driver and later bound, if there was another dynamic misc device registered in between, it would fail to register the acpi_thermal_rel misc device. Other drivers behave similarly. Actually, this kind of issue is prone to happen if APIs misc_register()/misc_deregister() are invoked by driver's probe()/remove() separately. Instead of fixing all the drivers, just reset the minor member to MISC_DYNAMIC_MINOR in misc_deregister() in case it was a dynamically allocated minor number, as error handling of misc_register() does. Cc: Thadeu Lima de Souza Cascardo <cascardo@igalia.com> Signed-off-by: Zijun Hu <zijun.hu@oss.qualcomm.com> Link: https://lore.kernel.org/r/20250714-rfc_miscdev-v6-5-2ed949665bde@oss.qualcomm.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 52e2bb5ff089d65e2c7d982fe2826dc88e473d50 ]

For miscdevice who wants dynamic minor, it may fail to be registered again
without reinitialization after being de-registered, which is illustrated
by kunit test case miscdev_test_dynamic_reentry() newly added.

There is a real case found by cascardo when a part of minor range were
contained by range [0, 255):

1) wmi/dell-smbios registered minor 122, and acpi_thermal_rel registered
   minor 123
2) unbind "int3400 thermal" driver from its device, this will de-register
   acpi_thermal_rel
3) rmmod then insmod dell_smbios again, now wmi/dell-smbios is using minor
   123
4) bind the device to "int3400 thermal" driver again, acpi_thermal_rel
   fails to register.

Some drivers may reuse the miscdevice structure after they are deregistered
If the intention is to allocate a dynamic minor, if the minor number is not
reset to MISC_DYNAMIC_MINOR before calling misc_register(), it will try to
register a previously dynamically allocated minor number, which may have
been registered by a different driver.

One such case is the acpi_thermal_rel misc device, registered by the
int3400 thermal driver. If the device is unbound from the driver and later
bound, if there was another dynamic misc device registered in between, it
would fail to register the acpi_thermal_rel misc device. Other drivers
behave similarly.

Actually, this kind of issue is prone to happen if APIs
misc_register()/misc_deregister() are invoked by driver's
probe()/remove() separately.

Instead of fixing all the drivers, just reset the minor member to
MISC_DYNAMIC_MINOR in misc_deregister() in case it was a dynamically
allocated minor number, as error handling of misc_register() does.

Cc: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
Signed-off-by: Zijun Hu <zijun.hu@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20250714-rfc_miscdev-v6-5-2ed949665bde@oss.qualcomm.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
char: misc: Fix improper and inaccurate error code returned by misc_init() 2025-08-20T16:30:25+00:00 Zijun Hu zijun.hu@oss.qualcomm.com 2025-06-20T14:35:20+00:00 8152499f09ebea0e77980ef6d4f50d657176cc5c [ Upstream commit 0ef1fe4bc38673db72e39b700b29c50dfcc5a415 ] misc_init() returns -EIO for __register_chrdev() invocation failure, but: - -EIO is for I/O error normally, but __register_chrdev() does not do I/O. - -EIO can not cover various error codes returned by __register_chrdev(). Fix by returning error code of __register_chrdev(). Signed-off-by: Zijun Hu <zijun.hu@oss.qualcomm.com> Link: https://lore.kernel.org/r/20250620-fix_mischar-v1-3-6c2716bbf1fa@oss.qualcomm.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 0ef1fe4bc38673db72e39b700b29c50dfcc5a415 ]

misc_init() returns -EIO for __register_chrdev() invocation failure, but:

- -EIO is for I/O error normally, but __register_chrdev() does not do I/O.
- -EIO can not cover various error codes returned by __register_chrdev().

Fix by returning error code of __register_chrdev().

Signed-off-by: Zijun Hu <zijun.hu@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20250620-fix_mischar-v1-3-6c2716bbf1fa@oss.qualcomm.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
char: misc: register chrdev region with all possible minors 2025-05-02T05:59:10+00:00 Thadeu Lima de Souza Cascardo cascardo@igalia.com 2025-03-17T13:59:55+00:00 3670dee37657ea0c812161c838e7fde99471c846 commit c876be906ce7e518d9ef9926478669c151999e69 upstream. register_chrdev will only register the first 256 minors of a major chrdev. That means that dynamically allocated misc devices with minor above 255 will fail to open with -ENXIO. This was found by kernel test robot when testing a different change that makes all dynamically allocated minors be above 255. This has, however, been separately tested by creating 256 serio_raw devices with the help of userio driver. Ever since allowing misc devices with minors above 128, this has been possible. Fix it by registering all minor numbers from 0 to MINORMASK + 1 for MISC_MAJOR. Reported-by: kernel test robot <oliver.sang@intel.com> Cc: stable <stable@kernel.org> Closes: https://lore.kernel.org/oe-lkp/202503171507.6c8093d0-lkp@intel.com Fixes: ab760791c0cf ("char: misc: Increase the maximum number of dynamic misc devices to 1048448") Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com> Tested-by: Hou Wenlong <houwenlong.hwl@antgroup.com> Link: https://lore.kernel.org/r/20250317-misc-chrdev-v1-1-6cd05da11aef@igalia.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit c876be906ce7e518d9ef9926478669c151999e69 upstream.

register_chrdev will only register the first 256 minors of a major chrdev.
That means that dynamically allocated misc devices with minor above 255
will fail to open with -ENXIO.

This was found by kernel test robot when testing a different change that
makes all dynamically allocated minors be above 255. This has, however,
been separately tested by creating 256 serio_raw devices with the help of
userio driver.

Ever since allowing misc devices with minors above 128, this has been
possible.

Fix it by registering all minor numbers from 0 to MINORMASK + 1 for
MISC_MAJOR.

Reported-by: kernel test robot <oliver.sang@intel.com>
Cc: stable <stable@kernel.org>
Closes: https://lore.kernel.org/oe-lkp/202503171507.6c8093d0-lkp@intel.com
Fixes: ab760791c0cf ("char: misc: Increase the maximum number of dynamic misc devices to 1048448")
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
Tested-by: Hou Wenlong <houwenlong.hwl@antgroup.com>
Link: https://lore.kernel.org/r/20250317-misc-chrdev-v1-1-6cd05da11aef@igalia.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
char: misc: deallocate static minor in error path 2025-03-13T12:02:15+00:00 Thadeu Lima de Souza Cascardo cascardo@igalia.com 2025-01-23T12:32:49+00:00 4e8df56636e3f525e02bb068deb998c70fd0813a commit 6d991f569c5ef6eaeadf1238df2c36e3975233ad upstream. When creating sysfs files fail, the allocated minor must be freed such that it can be later reused. That is specially harmful for static minor numbers, since those would always fail to register later on. Fixes: 6d04d2b554b1 ("misc: misc_minor_alloc to use ida for all dynamic/misc dynamic minors") Cc: stable <stable@kernel.org> Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com> Link: https://lore.kernel.org/r/20250123123249.4081674-5-cascardo@igalia.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 6d991f569c5ef6eaeadf1238df2c36e3975233ad upstream.

When creating sysfs files fail, the allocated minor must be freed such that
it can be later reused. That is specially harmful for static minor numbers,
since those would always fail to register later on.

Fixes: 6d04d2b554b1 ("misc: misc_minor_alloc to use ida for all dynamic/misc dynamic minors")
Cc: stable <stable@kernel.org>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
Link: https://lore.kernel.org/r/20250123123249.4081674-5-cascardo@igalia.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
misc: misc_minor_alloc to use ida for all dynamic/misc dynamic minors 2025-02-17T09:05:41+00:00 Vimal Agrawal vimal.agrawal@sophos.com 2024-10-21T13:38:12+00:00 8b4120b3e060e137eaa8dc76a1c40401088336e5 commit 6d04d2b554b14ae6c428a9c60b6c85f1e5c89f68 upstream. misc_minor_alloc was allocating id using ida for minor only in case of MISC_DYNAMIC_MINOR but misc_minor_free was always freeing ids using ida_free causing a mismatch and following warn: > > WARNING: CPU: 0 PID: 159 at lib/idr.c:525 ida_free+0x3e0/0x41f > > ida_free called for id=127 which is not allocated. > > <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< ... > > [<60941eb4>] ida_free+0x3e0/0x41f > > [<605ac993>] misc_minor_free+0x3e/0xbc > > [<605acb82>] misc_deregister+0x171/0x1b3 misc_minor_alloc is changed to allocate id from ida for all minors falling in the range of dynamic/ misc dynamic minors Fixes: ab760791c0cf ("char: misc: Increase the maximum number of dynamic misc devices to 1048448") Signed-off-by: Vimal Agrawal <vimal.agrawal@sophos.com> Reviewed-by: Dirk VanDerMerwe <dirk.vandermerwe@sophos.com> Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20241021133812.23703-1-vimal.agrawal@sophos.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 6d04d2b554b14ae6c428a9c60b6c85f1e5c89f68 upstream.

misc_minor_alloc was allocating id using ida for minor only in case of
MISC_DYNAMIC_MINOR but misc_minor_free was always freeing ids
using ida_free causing a mismatch and following warn:
> > WARNING: CPU: 0 PID: 159 at lib/idr.c:525 ida_free+0x3e0/0x41f
> > ida_free called for id=127 which is not allocated.
> > <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
...
> > [<60941eb4>] ida_free+0x3e0/0x41f
> > [<605ac993>] misc_minor_free+0x3e/0xbc
> > [<605acb82>] misc_deregister+0x171/0x1b3

misc_minor_alloc is changed to allocate id from ida for all minors
falling in the range of dynamic/ misc dynamic minors

Fixes: ab760791c0cf ("char: misc: Increase the maximum number of dynamic misc devices to 1048448")
Signed-off-by: Vimal Agrawal <vimal.agrawal@sophos.com>
Reviewed-by: Dirk VanDerMerwe <dirk.vandermerwe@sophos.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20241021133812.23703-1-vimal.agrawal@sophos.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
char: misc: make misc_class a static const structure 2023-06-23T08:27:15+00:00 Ivan Orlov ivan.orlov0322@gmail.com 2023-06-20T14:37:56+00:00 eafd52e6971ab63dd9294df1e363951148f292cf Now that the driver core allows for struct class to be in read-only memory, move the misc_class structure to be declared at build time placing it into read-only memory, instead of having to be dynamically allocated at load time. Cc: Arnd Bergmann <arnd@arndb.de> Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Ivan Orlov <ivan.orlov0322@gmail.com> Link: https://lore.kernel.org/r/20230620143751.578239-14-gregkh@linuxfoundation.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
Now that the driver core allows for struct class to be in read-only
memory, move the misc_class structure to be declared at build time
placing it into read-only memory, instead of having to be dynamically
allocated at load time.

Cc: Arnd Bergmann <arnd@arndb.de>
Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ivan Orlov <ivan.orlov0322@gmail.com>
Link: https://lore.kernel.org/r/20230620143751.578239-14-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
driver core: class: remove module * from class_create() 2023-03-17T14:16:33+00:00 Greg Kroah-Hartman gregkh@linuxfoundation.org 2023-03-13T18:18:35+00:00 1aaba11da9aa7d7d6b52a74d45b31cac118295a1 The module pointer in class_create() never actually did anything, and it shouldn't have been requred to be set as a parameter even if it did something. So just remove it and fix up all callers of the function in the kernel tree at the same time. Cc: "Rafael J. Wysocki" <rafael@kernel.org> Acked-by: Benjamin Tissoires <benjamin.tissoires@redhat.com> Link: https://lore.kernel.org/r/20230313181843.1207845-4-gregkh@linuxfoundation.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
The module pointer in class_create() never actually did anything, and it
shouldn't have been requred to be set as a parameter even if it did
something.  So just remove it and fix up all callers of the function in
the kernel tree at the same time.

Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Acked-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Link: https://lore.kernel.org/r/20230313181843.1207845-4-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>