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Message-Id: <20241015070226.15790-1-vimal.agrawal@sophos.com>
Date: Tue, 15 Oct 2024 07:02:26 +0000
From: Vimal Agrawal <avimalin@...il.com>
To: linux-kernel@...r.kernel.org,
gregkh@...uxfoundation.org,
arnd@...db.de
Cc: avimalin@...il.com,
vimal.agrawal@...hos.com
Subject: [PATCH v2] 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: 0ad35fed618c ("char: misc: Increase the maximum number of dynamic misc devices to 1048448")
Signed-off-by: Vimal Agrawal <vimal.agrawal@...hos.com>
---
drivers/char/misc.c | 35 +++++++++++++++++-----
lib/Kconfig.debug | 11 +++++++
lib/Makefile | 1 +
lib/test_misc_minor.c | 67 +++++++++++++++++++++++++++++++++++++++++++
4 files changed, 107 insertions(+), 7 deletions(-)
create mode 100644 lib/test_misc_minor.c
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);
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..bcec3fb1c46a
--- /dev/null
+++ b/lib/test_misc_minor.c
@@ -0,0 +1,67 @@
+// 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");
--
2.17.1
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