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Message-Id: <20241017114329.22351-2-vimal.agrawal@sophos.com>
Date: Thu, 17 Oct 2024 11:43:29 +0000
From: Vimal Agrawal <avimalin@...il.com>
To: linux-kernel@...r.kernel.org,
gregkh@...uxfoundation.org,
arnd@...db.de,
quic_jjohnson@...cinc.com,
dan.carpenter@...aro.org
Cc: avimalin@...il.com,
vimal.agrawal@...hos.com,
stable@...r.kernel.org
Subject: [PATCH v3 1/2] 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: ab760791c0cf ("char: misc: Increase the maximum number of dynamic misc devices to 1048448")
Signed-off-by: Vimal Agrawal <vimal.agrawal@...hos.com>
Cc: stable@...r.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
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