linux-kernel - [PATCH v4 5/8] char: misc: Make registering miscdevice reentry who wants dynamic minor

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20250704-rfc_miscdev-v4-5-b48986112d6a@oss.qualcomm.com>
Date: Fri, 04 Jul 2025 21:26:03 +0800
From: Zijun Hu <zijun_hu@...oud.com>
To: Arnd Bergmann <arnd@...db.de>, 
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
 "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>, 
 Helge Deller <deller@....de>, "David S. Miller" <davem@...emloft.net>, 
 Andreas Larsson <andreas@...sler.com>
Cc: Thadeu Lima de Souza Cascardo <cascardo@...lia.com>, 
 Zijun Hu <zijun_hu@...oud.com>, linux-kernel@...r.kernel.org, 
 linux-parisc@...r.kernel.org, sparclinux@...r.kernel.org, 
 Zijun Hu <zijun.hu@....qualcomm.com>
Subject: [PATCH v4 5/8] char: misc: Make registering miscdevice reentry who
 wants dynamic minor

From: Zijun Hu <zijun.hu@....qualcomm.com>

misc_deregister() frees dynamic minor @misc->minor but does not reset it
and cause kunit test case miscdev_test_dynamic_reentry() failure:

| Invalid fixed minor 257 for miscdevice 'miscdyn_a'
| #miscdev_test_dynamic_reentry: ASSERTION FAILED at misc_minor_kunit.c:639
| Expected ret == 0, but
| ret == -22 (0xffffffffffffffea)
| [FAILED] miscdev_test_dynamic_reentry

misc_register()/misc_deregister() are sometimes invoked by driver's
probe()/remove() separately, which has reentry requirement.

Fix by resetting @misc->minor to MISC_DYNAMIC_MINOR in misc_deregister()
as error handling of misc_register() does.

Signed-off-by: Zijun Hu <zijun.hu@....qualcomm.com>
---
 drivers/char/misc.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/char/misc.c b/drivers/char/misc.c
index b8e66466184fa21fb66d968db7950e0b5669ac43..96ed343cf5c8509a09855020049a9af82a3ede95 100644
--- a/drivers/char/misc.c
+++ b/drivers/char/misc.c
@@ -288,6 +288,8 @@ void misc_deregister(struct miscdevice *misc)
 	list_del(&misc->list);
 	device_destroy(&misc_class, MKDEV(MISC_MAJOR, misc->minor));
 	misc_minor_free(misc->minor);
+	if (misc->minor > MISC_DYNAMIC_MINOR)
+		misc->minor = MISC_DYNAMIC_MINOR;
 	mutex_unlock(&misc_mtx);
 }
 EXPORT_SYMBOL(misc_deregister);

-- 
2.34.1