| Message ID | 20220331023608.30497-1-xiam0nd.tong@gmail.com (mailing list archive) |
|---|---|
| State | Superseded, archived |
| Headers | show |
| Series | [v2] opp: use list iterator only inside the loop | expand |
On 31-03-22, 10:36, Xiaomeng Tong wrote: > 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;'. There is no such bug as I explained earlier, why you added this again despite being discussed ? > As discussed before, I just told you not to use such language as this will go in logs, but you still chose to add it :( > 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);. Please look at this on how to write the log, which fixes a very similar problem. https://lore.kernel.org/all/20220324071815.61405-1-jakobkoschel@gmail.com/ > > [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
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;
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(-)