lkml.org 
[lkml]   [2022]   [Mar]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v2] opp: use list iterator only inside the loop
Date
The list iterator 'new_dev' will point to a bogus position containing
HEAD if any one of these conditions is possible: the list is empty or
no element is found, thus can potentially lead to an invalid memory
access in 'dev = new_dev->dev;'.

As discussed before, we should avoid to use a list iterator variable
outside the loop which is considered harmful[1].

In this case, use a new variable 'iter' as the list iterator, while
use the old variable 'new_dev' as a dedicated pointer to point to the
found entry. And BUG_ON(!new_dev);.

[1]: https://lkml.org/lkml/2022/2/17/1032

Signed-off-by: Xiaomeng Tong <xiam0nd.tong@gmail.com>
---

changes since v1:
- use BUG_ON(!new_dev); instead of return; (Viresh Kumar)

v1: https://lore.kernel.org/lkml/20220331015818.28045-1-xiam0nd.tong@gmail.com/

---
drivers/opp/debugfs.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/opp/debugfs.c b/drivers/opp/debugfs.c
index 596c185b5dda..81b2bc4b5f43 100644
--- a/drivers/opp/debugfs.c
+++ b/drivers/opp/debugfs.c
@@ -187,14 +187,18 @@ void opp_debug_register(struct opp_device *opp_dev, struct opp_table *opp_table)
static void opp_migrate_dentry(struct opp_device *opp_dev,
struct opp_table *opp_table)
{
- struct opp_device *new_dev;
+ struct opp_device *new_dev = NULL, *iter;
const struct device *dev;
struct dentry *dentry;

/* Look for next opp-dev */
- list_for_each_entry(new_dev, &opp_table->dev_list, node)
- if (new_dev != opp_dev)
+ list_for_each_entry(iter, &opp_table->dev_list, node)
+ if (iter != opp_dev) {
+ new_dev = iter;
break;
+ }
+
+ BUG_ON(!new_dev);

/* new_dev is guaranteed to be valid here */
dev = new_dev->dev;
--
2.17.1
\
 
 \ /
  Last update: 2022-03-31 04:37    [W:0.046 / U:22.216 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site