From: Prateek Sood <prsood@codeaurora.org>
To: gregkh@linuxfoundation.org, rafael@kernel.org
Cc: sramana@codeaurora.org, prsood@codeaurora.org,
linux-kernel@vger.kernel.org
Subject: [PATCH V2] drivers: core: Remove glue dirs early only when refcount is 1
Date: Wed, 1 May 2019 09:52:47 +0530 [thread overview]
Message-ID: <1556684567-26710-1-git-send-email-prsood@codeaurora.org> (raw)
In-Reply-To: <1556632540-17382-1-git-send-email-prsood@codeaurora.org>
While loading firmware blobs parallely in different threads, it is possible
to free sysfs node of glue_dirs in device_del() from a thread while another
thread is trying to add subdir from device_add() in glue_dirs sysfs node.
CPU1 CPU2
fw_load_sysfs_fallback()
device_add()
get_device_parent()
class_dir_create_and_add()
kobject_add_internal()
create_dir() // glue_dir
fw_load_sysfs_fallback()
device_add()
get_device_parent()
kobject_get() //glue_dir
device_del()
cleanup_glue_dir()
kobject_del()
kobject_add()
kobject_add_internal()
create_dir() // in glue_dir
kernfs_create_dir_ns()
sysfs_remove_dir() //glue_dir->sd=NULL
sysfs_put() // free glue_dir->sd
kernfs_new_node()
kernfs_get(glue_dir)
Fix this race by making sure that kernfs_node for glue_dir is released only
when refcount for glue_dir kobj is 1.
Signed-off-by: Prateek Sood <prsood@codeaurora.org>
---
drivers/base/core.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/base/core.c b/drivers/base/core.c
index 4aeaa0c..3955d07 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -1820,12 +1820,15 @@ static inline struct kobject *get_glue_dir(struct device *dev)
*/
static void cleanup_glue_dir(struct device *dev, struct kobject *glue_dir)
{
+ unsigned int refcount;
+
/* see if we live in a "glue" directory */
if (!live_in_glue_dir(glue_dir, dev))
return;
mutex_lock(&gdp_mutex);
- if (!kobject_has_children(glue_dir))
+ refcount = kref_read(&glue_dir->kref);
+ if (!kobject_has_children(glue_dir) && !--refcount)
kobject_del(glue_dir);
kobject_put(glue_dir);
mutex_unlock(&gdp_mutex);
--
Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc.,
is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.
next prev parent reply other threads:[~2019-05-01 4:23 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-30 13:55 [PATCH] drivers: core: Remove glue dirs early only when refcount is 1 Prateek Sood
2019-05-01 4:22 ` Prateek Sood [this message]
2019-05-01 6:53 ` [PATCH V2] " Greg KH
2019-05-01 11:59 ` [PATCH v3] " Prateek Sood
2019-05-06 5:11 ` Prateek Sood
2019-05-06 6:21 ` Greg KH
2019-05-24 19:04 ` Greg KH
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