[PATCH v3 1/2] misc: misc_minor_alloc to use ida for all dynamic/misc dynamic minors

[PATCH v3 1/2] misc: misc_minor_alloc to use ida for all dynamic/misc dynamic minors

[Vimal Agrawal]

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>
Cc: stable@vger.kernel.org
---
v2: Added Fixes:
    added missed case for static minor in misc_minor_alloc
v3: removed kunit changes as that will be added as second patch in this two patch series

 drivers/char/misc.c | 35 ++++++++++++++++++++++++++++-------
 1 file changed, 28 insertions(+), 7 deletions(-)

diff --git a/drivers/char/misc.c b/drivers/char/misc.c
index 541edc26ec89..9d0cd3459b4f 100644
--- a/drivers/char/misc.c
+++ b/drivers/char/misc.c
@@ -63,16 +63,30 @@ 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;
 
-	ret = ida_alloc_max(&misc_minors_ida, DYNAMIC_MINORS - 1, GFP_KERNEL);
-	if (ret >= 0) {
-		ret = DYNAMIC_MINORS - ret - 1;
-	} else {
-		ret = ida_alloc_range(&misc_minors_ida, MISC_DYNAMIC_MINOR + 1,
+	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;
+		} else {
+			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);
-- 
2.17.1

Re: [PATCH v3 1/2] misc: misc_minor_alloc to use ida for all dynamic/misc dynamic minors

[Greg KH]

On Thu, Oct 17, 2024 at 10:53:25AM +0000, Vimal Agrawal wrote:
> 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>
> Cc: stable@vger.kernel.org
> ---
> v2: Added Fixes:
>     added missed case for static minor in misc_minor_alloc
> v3: removed kunit changes as that will be added as second patch in this two patch series
> 
>  drivers/char/misc.c | 35 ++++++++++++++++++++++++++++-------
>  1 file changed, 28 insertions(+), 7 deletions(-)

Did you mean to send this only to stable and yourself and not the
maintainers involved here?

confused,

greg k-h

Re: [PATCH v2] misc: misc_minor_alloc to use ida for all dynamic/misc dynamic minors

[Vimal Agrawal]

Hi Jeff,

Thanks. I will be adding MODULE_DESCRIPTION in the next version of the
patch. Will be splitting kunit changes from this patch in two patch
series.

Vimal

On Wed, Oct 16, 2024 at 3:48 AM Jeff Johnson <quic_jjohnson@quicinc.com> wrote:
>
> On 10/15/24 00:02, Vimal Agrawal wrote:
> ...
> > +static struct kunit_suite test_suite = {
> > +     .name = "misc_minor_test",
> > +     .test_cases = test_cases,
> > +};
> > +kunit_test_suite(test_suite);
> > +
> > +MODULE_LICENSE("GPL");
>
> Since commit 1fffe7a34c89 ("script: modpost: emit a warning when the
> description is missing"), a module without a MODULE_DESCRIPTION() will
> result in a warning when built with make W=1. Recently, multiple
> developers have been eradicating these warnings treewide, and very few
> (if any) are left, so please don't introduce a new one :)
>
> Please add the missing MODULE_DESCRIPTION()
>
> /jeff

[PATCH v1 2/2] misc:minor basic kunit tests

[Vimal Agrawal]

basic kunit tests for misc minor

Signed-off-by: Vimal Agrawal <vimal.agrawal@sophos.com>
---
 lib/Kconfig.debug     | 11 +++++++
 lib/Makefile          |  1 +
 lib/test_misc_minor.c | 69 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 81 insertions(+)
 create mode 100644 lib/test_misc_minor.c

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 7315f643817a..5a5d27284e0a 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -2488,6 +2488,17 @@ config TEST_RHASHTABLE
 config TEST_IDA
 	tristate "Perform selftest on IDA functions"
 
+config TEST_MISC_MINOR
+	tristate "Basic misc minor Kunit test" if !KUNIT_ALL_TESTS
+	depends on KUNIT
+	default KUNIT_ALL_TESTS
+	help
+	  Kunit test for the misc minor.
+	  It tests misc minor functions for dynamic and misc dynamic minor.
+	  This include misc_xxx functions
+
+	  If unsure, say N.
+
 config TEST_PARMAN
 	tristate "Perform selftest on priority array manager"
 	depends on PARMAN
diff --git a/lib/Makefile b/lib/Makefile
index 773adf88af41..631d73f96f76 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -68,6 +68,7 @@ obj-$(CONFIG_TEST_SYSCTL) += test_sysctl.o
 obj-$(CONFIG_TEST_IOV_ITER) += kunit_iov_iter.o
 obj-$(CONFIG_HASH_KUNIT_TEST) += test_hash.o
 obj-$(CONFIG_TEST_IDA) += test_ida.o
+obj-$(CONFIG_TEST_MISC_MINOR) += test_misc_minor.o
 obj-$(CONFIG_TEST_UBSAN) += test_ubsan.o
 CFLAGS_test_ubsan.o += $(call cc-disable-warning, vla)
 CFLAGS_test_ubsan.o += $(call cc-disable-warning, unused-but-set-variable)
diff --git a/lib/test_misc_minor.c b/lib/test_misc_minor.c
new file mode 100644
index 000000000000..293e0fb7e43e
--- /dev/null
+++ b/lib/test_misc_minor.c
@@ -0,0 +1,69 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <kunit/test.h>
+#include <kunit/test-bug.h>
+#include <linux/module.h>
+#include <linux/miscdevice.h>
+
+/* dynamic minor (2) */
+static struct miscdevice dev_dynamic_minor = {
+	.minor  = 2,
+	.name   = "dev_dynamic_minor",
+};
+
+/* static minor (LCD_MINOR) */
+static struct miscdevice dev_static_minor = {
+	.minor  = LCD_MINOR,
+	.name   = "dev_static_minor",
+};
+
+/* misc dynamic minor */
+static struct miscdevice dev_misc_dynamic_minor = {
+	.minor  = MISC_DYNAMIC_MINOR,
+	.name   = "dev_misc_dynamic_minor",
+};
+
+static void kunit_dynamic_minor(struct kunit *test)
+{
+	int ret;
+
+	ret = misc_register(&dev_dynamic_minor);
+	KUNIT_EXPECT_EQ(test, 0, ret);
+	KUNIT_EXPECT_EQ(test, 2, dev_dynamic_minor.minor);
+	misc_deregister(&dev_dynamic_minor);
+}
+
+static void kunit_static_minor(struct kunit *test)
+{
+	int ret;
+
+	ret = misc_register(&dev_static_minor);
+	KUNIT_EXPECT_EQ(test, 0, ret);
+	KUNIT_EXPECT_EQ(test, LCD_MINOR, dev_static_minor.minor);
+	misc_deregister(&dev_static_minor);
+}
+
+static void kunit_misc_dynamic_minor(struct kunit *test)
+{
+	int ret;
+
+	ret = misc_register(&dev_misc_dynamic_minor);
+	KUNIT_EXPECT_EQ(test, 0, ret);
+	misc_deregister(&dev_misc_dynamic_minor);
+}
+
+static struct kunit_case test_cases[] = {
+	KUNIT_CASE(kunit_dynamic_minor),
+	KUNIT_CASE(kunit_static_minor),
+	KUNIT_CASE(kunit_misc_dynamic_minor),
+	{}
+};
+
+static struct kunit_suite test_suite = {
+	.name = "misc_minor_test",
+	.test_cases = test_cases,
+};
+kunit_test_suite(test_suite);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Vimal Agrawal");
+MODULE_DESCRIPTION("misc minor testing");
-- 
2.17.1

[PATCH v3 1/2] misc: misc_minor_alloc to use ida for all dynamic/misc dynamic minors

[Vimal Agrawal]

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>
Cc: stable@vger.kernel.org
---
v2: Added Fixes:
    added missed case for static minor in misc_minor_alloc
v3: removed kunit changes as that will be added as second patch in this two patch series

 drivers/char/misc.c | 35 ++++++++++++++++++++++++++++-------
 1 file changed, 28 insertions(+), 7 deletions(-)

diff --git a/drivers/char/misc.c b/drivers/char/misc.c
index 541edc26ec89..9d0cd3459b4f 100644
--- a/drivers/char/misc.c
+++ b/drivers/char/misc.c
@@ -63,16 +63,30 @@ 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 = 0;
 
-	ret = ida_alloc_max(&misc_minors_ida, DYNAMIC_MINORS - 1, GFP_KERNEL);
-	if (ret >= 0) {
-		ret = DYNAMIC_MINORS - ret - 1;
-	} else {
-		ret = ida_alloc_range(&misc_minors_ida, MISC_DYNAMIC_MINOR + 1,
+	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;
+		} else {
+			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);
-- 
2.17.1