Commit 6d04d2b5 authored by Vimal Agrawal's avatar Vimal Agrawal Committed by Greg Kroah-Hartman
Browse files

misc: misc_minor_alloc to use ida for all dynamic/misc dynamic minors 



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: ab760791 ("char: misc: Increase the maximum number of dynamic misc devices to 1048448")
Signed-off-by: default avatarVimal Agrawal <vimal.agrawal@sophos.com>
Reviewed-by: default avatarDirk 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: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 567a311d

drivers/char/misc.c

+30 −9
Original line number Diff line number Diff line
@@ -63,10 +63,12 @@ static DEFINE_MUTEX(misc_mtx); 
#define DYNAMIC_MINORS 128 /* like dynamic majors */

static DEFINE_IDA(misc_minors_ida);



static int misc_minor_alloc(void)

static int misc_minor_alloc(int minor)

{

	int ret;

	int ret = 0;



	if (minor == MISC_DYNAMIC_MINOR) {

		/* allocate free id */

		ret = ida_alloc_max(&misc_minors_ida, DYNAMIC_MINORS - 1, GFP_KERNEL);

		if (ret >= 0) {

			ret = DYNAMIC_MINORS - ret - 1;
@@ -74,6 +76,18 @@ static int misc_minor_alloc(void) 
			ret = ida_alloc_range(&misc_minors_ida, MISC_DYNAMIC_MINOR + 1,

					      MINORMASK, GFP_KERNEL);

		}

	} else {

		/* specific minor, check if it is in dynamic or misc dynamic range  */

		if (minor < DYNAMIC_MINORS) {

			minor = DYNAMIC_MINORS - minor - 1;

			ret = ida_alloc_range(&misc_minors_ida, minor, minor, GFP_KERNEL);

		} else if (minor > MISC_DYNAMIC_MINOR) {

			ret = ida_alloc_range(&misc_minors_ida, minor, minor, GFP_KERNEL);

		} else {

			/* case of non-dynamic minors, no need to allocate id */

			ret = 0;

		}

	}

	return ret;

}
@@ -219,7 +233,7 @@ int misc_register(struct miscdevice *misc) 
	mutex_lock(&misc_mtx);



	if (is_dynamic) {

		int i = misc_minor_alloc();

		int i = misc_minor_alloc(misc->minor);



		if (i < 0) {

			err = -EBUSY;
@@ -228,6 +242,7 @@ int misc_register(struct miscdevice *misc) 
		misc->minor = i;

	} else {

		struct miscdevice *c;

		int i;



		list_for_each_entry(c, &misc_list, list) {

			if (c->minor == misc->minor) {
@@ -235,6 +250,12 @@ int misc_register(struct miscdevice *misc) 
				goto out;

			}

		}



		i = misc_minor_alloc(misc->minor);

		if (i < 0) {

			err = -EBUSY;

			goto out;

		}

	}



	dev = MKDEV(MISC_MAJOR, misc->minor);