From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4A9171862BD; Mon, 12 Aug 2024 16:21:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723479686; cv=none; b=PkkQpLX6xmndneDmg59lM15dAtwIDgJPe1EmnaH5soLCPTlHZ2fWHK6e5ZjXlBcV/jO2M0pxpULw1w/GJWigNUSpv2CgOduRj0RuZAF9VkqaM4Wus9Y16d2zSBhMwWg8ukypc2DTKXlO1gGqGQz/gAr0IlRYIE12XozLkzq6ocM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723479686; c=relaxed/simple; bh=Sy3IhrzYsH12cNk3LBZRqgYbWyhHCWSB0o8YH0UQzgk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=YsF7B6zWAvi9lu+d+aSlvVYZzodi2XSEv19EejNTjQkI2Zx24UI9yiNjSabgw5U68MzS789BpUQCzl5Zd4YBQRcDXbFfRZRzUWA6i8MD6gO+7oFyMsUO8wMAKJ9CDBQRe9i+O8VOk/1Hh3kT6+uxluLNSiLcCxJv2QaoCOoTdlA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=GAnOfRRF; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="GAnOfRRF" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4974BC4AF09; Mon, 12 Aug 2024 16:21:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1723479685; bh=Sy3IhrzYsH12cNk3LBZRqgYbWyhHCWSB0o8YH0UQzgk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=GAnOfRRFOaDNwx6EjvX7m4xLXOdFl60cj7r+z1vzXmm26L5utFTdz6UzplWjN/tYK MzW8A2I9O9olmOUHy+DHuTBTiRcO46GiGOpSeNXrbT2PEwmkAOLip3DY21f/grNrWd ENC3XwUb5fujsVA0kM/0R+XL7X2LwatJlhw6unhQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+4762dd74e32532cda5ff@syzkaller.appspotmail.com, Tetsuo Handa , Ashish Sangwan , Namjae Jeon , Dirk Behme , "Rafael J. Wysocki" , Dan Williams Subject: [PATCH 6.6 131/189] driver core: Fix uevent_show() vs driver detach race Date: Mon, 12 Aug 2024 18:03:07 +0200 Message-ID: <20240812160137.186258579@linuxfoundation.org> X-Mailer: git-send-email 2.46.0 In-Reply-To: <20240812160132.135168257@linuxfoundation.org> References: <20240812160132.135168257@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Dan Williams commit 15fffc6a5624b13b428bb1c6e9088e32a55eb82c upstream. uevent_show() wants to de-reference dev->driver->name. There is no clean way for a device attribute to de-reference dev->driver unless that attribute is defined via (struct device_driver).dev_groups. Instead, the anti-pattern of taking the device_lock() in the attribute handler risks deadlocks with code paths that remove device attributes while holding the lock. This deadlock is typically invisible to lockdep given the device_lock() is marked lockdep_set_novalidate_class(), but some subsystems allocate a local lockdep key for @dev->mutex to reveal reports of the form: ====================================================== WARNING: possible circular locking dependency detected 6.10.0-rc7+ #275 Tainted: G OE N ------------------------------------------------------ modprobe/2374 is trying to acquire lock: ffff8c2270070de0 (kn->active#6){++++}-{0:0}, at: __kernfs_remove+0xde/0x220 but task is already holding lock: ffff8c22016e88f8 (&cxl_root_key){+.+.}-{3:3}, at: device_release_driver_internal+0x39/0x210 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&cxl_root_key){+.+.}-{3:3}: __mutex_lock+0x99/0xc30 uevent_show+0xac/0x130 dev_attr_show+0x18/0x40 sysfs_kf_seq_show+0xac/0xf0 seq_read_iter+0x110/0x450 vfs_read+0x25b/0x340 ksys_read+0x67/0xf0 do_syscall_64+0x75/0x190 entry_SYSCALL_64_after_hwframe+0x76/0x7e -> #0 (kn->active#6){++++}-{0:0}: __lock_acquire+0x121a/0x1fa0 lock_acquire+0xd6/0x2e0 kernfs_drain+0x1e9/0x200 __kernfs_remove+0xde/0x220 kernfs_remove_by_name_ns+0x5e/0xa0 device_del+0x168/0x410 device_unregister+0x13/0x60 devres_release_all+0xb8/0x110 device_unbind_cleanup+0xe/0x70 device_release_driver_internal+0x1c7/0x210 driver_detach+0x47/0x90 bus_remove_driver+0x6c/0xf0 cxl_acpi_exit+0xc/0x11 [cxl_acpi] __do_sys_delete_module.isra.0+0x181/0x260 do_syscall_64+0x75/0x190 entry_SYSCALL_64_after_hwframe+0x76/0x7e The observation though is that driver objects are typically much longer lived than device objects. It is reasonable to perform lockless de-reference of a @driver pointer even if it is racing detach from a device. Given the infrequency of driver unregistration, use synchronize_rcu() in module_remove_driver() to close any potential races. It is potentially overkill to suffer synchronize_rcu() just to handle the rare module removal racing uevent_show() event. Thanks to Tetsuo Handa for the debug analysis of the syzbot report [1]. Fixes: c0a40097f0bc ("drivers: core: synchronize really_probe() and dev_uevent()") Reported-by: syzbot+4762dd74e32532cda5ff@syzkaller.appspotmail.com Reported-by: Tetsuo Handa Closes: http://lore.kernel.org/5aa5558f-90a4-4864-b1b1-5d6784c5607d@I-love.SAKURA.ne.jp [1] Link: http://lore.kernel.org/669073b8ea479_5fffa294c1@dwillia2-xfh.jf.intel.com.notmuch Cc: stable@vger.kernel.org Cc: Ashish Sangwan Cc: Namjae Jeon Cc: Dirk Behme Cc: Greg Kroah-Hartman Cc: Rafael J. Wysocki Signed-off-by: Dan Williams Link: https://lore.kernel.org/r/172081332794.577428.9738802016494057132.stgit@dwillia2-xfh.jf.intel.com Signed-off-by: Greg Kroah-Hartman --- drivers/base/core.c | 13 ++++++++----- drivers/base/module.c | 4 ++++ 2 files changed, 12 insertions(+), 5 deletions(-) --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -25,6 +25,7 @@ #include #include #include +#include #include #include #include @@ -2565,6 +2566,7 @@ static const char *dev_uevent_name(const static int dev_uevent(const struct kobject *kobj, struct kobj_uevent_env *env) { const struct device *dev = kobj_to_dev(kobj); + struct device_driver *driver; int retval = 0; /* add device node properties if present */ @@ -2593,8 +2595,12 @@ static int dev_uevent(const struct kobje if (dev->type && dev->type->name) add_uevent_var(env, "DEVTYPE=%s", dev->type->name); - if (dev->driver) - add_uevent_var(env, "DRIVER=%s", dev->driver->name); + /* Synchronize with module_remove_driver() */ + rcu_read_lock(); + driver = READ_ONCE(dev->driver); + if (driver) + add_uevent_var(env, "DRIVER=%s", driver->name); + rcu_read_unlock(); /* Add common DT information about the device */ of_device_uevent(dev, env); @@ -2664,11 +2670,8 @@ static ssize_t uevent_show(struct device if (!env) return -ENOMEM; - /* Synchronize with really_probe() */ - device_lock(dev); /* let the kset specific function add its keys */ retval = kset->uevent_ops->uevent(&dev->kobj, env); - device_unlock(dev); if (retval) goto out; --- a/drivers/base/module.c +++ b/drivers/base/module.c @@ -7,6 +7,7 @@ #include #include #include +#include #include "base.h" static char *make_driver_name(struct device_driver *drv) @@ -97,6 +98,9 @@ void module_remove_driver(struct device_ if (!drv) return; + /* Synchronize with dev_uevent() */ + synchronize_rcu(); + sysfs_remove_link(&drv->p->kobj, "module"); if (drv->owner)