* [PATCH 0/1] misc: remove ineffective WARN_ON() check from misc_deregister()
@ 2025-08-27 2:40 xion.wang
2025-08-27 2:41 ` [PATCH 1/1] " xion.wang
0 siblings, 1 reply; 2+ messages in thread
From: xion.wang @ 2025-08-27 2:40 UTC (permalink / raw)
To: Arnd Bergmann, Greg Kroah-Hartman, Matthias Brugger,
AngeloGioacchino Del Regno
Cc: wsd_upstream, huadian.liu, Xion Wang, linux-kernel,
linux-arm-kernel, linux-mediatek
From: Xion Wang <xion.wang@mediatek.com>
Hi All,
This patch removes the ineffective WARN_ON(list_empty(&misc->list))
check from misc_deregister(). Please see the commit message for details.
Xion Wang (1):
misc: remove ineffective WARN_ON() check from misc_deregister()
drivers/char/misc.c | 3 ---
1 file changed, 3 deletions(-)
--
2.45.2
^ permalink raw reply [flat|nested] 2+ messages in thread
* [PATCH 1/1] misc: remove ineffective WARN_ON() check from misc_deregister()
2025-08-27 2:40 [PATCH 0/1] misc: remove ineffective WARN_ON() check from misc_deregister() xion.wang
@ 2025-08-27 2:41 ` xion.wang
0 siblings, 0 replies; 2+ messages in thread
From: xion.wang @ 2025-08-27 2:41 UTC (permalink / raw)
To: Arnd Bergmann, Greg Kroah-Hartman, Matthias Brugger,
AngeloGioacchino Del Regno
Cc: wsd_upstream, huadian.liu, Xion Wang, linux-kernel,
linux-arm-kernel, linux-mediatek
From: Xion Wang <xion.wang@mediatek.com>
The WARN_ON(list_empty(&misc->list)) in misc_deregister() does
not catch any practical error conditions:
- For statically allocated miscdevice structures, the list pointers
are zero-initialized, so list_empty() returns false, not true.
- After list_del(), the pointers are set to LIST_POISON1 and LIST_POISON2,
so repeated deregistration also fails to trigger the check.
Signed-off-by: Xion Wang <xion.wang@mediatek.com>
---
drivers/char/misc.c | 3 ---
1 file changed, 3 deletions(-)
diff --git a/drivers/char/misc.c b/drivers/char/misc.c
index 558302a64dd9..f46b00a76a59 100644
--- a/drivers/char/misc.c
+++ b/drivers/char/misc.c
@@ -275,9 +275,6 @@ EXPORT_SYMBOL(misc_register);
void misc_deregister(struct miscdevice *misc)
{
- if (WARN_ON(list_empty(&misc->list)))
- return;
-
mutex_lock(&misc_mtx);
list_del(&misc->list);
device_destroy(&misc_class, MKDEV(MISC_MAJOR, misc->minor));
--
2.45.2
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