| Message ID | 20220327053943.3071-1-xiam0nd.tong@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | opp: fix a missing check on list iterator | expand |
On 27-03-22, 13:39, Xiaomeng Tong wrote: > The bug is here: > dev = new_dev->dev; > > The list iterator 'new_dev' will point to a bogus position containing > HEAD if the list is empty or no element is found. This case must > be checked before any use of the iterator, otherwise it will lead > to a invalid memory access. > > To fix this bug, add an check. 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 element. > > Cc: stable@vger.kernel.org > Fixes: deaa51465105a ("PM / OPP: Add debugfs support") > Signed-off-by: Xiaomeng Tong <xiam0nd.tong@gmail.com> > --- > drivers/opp/debugfs.c | 11 ++++++++--- > 1 file changed, 8 insertions(+), 3 deletions(-) > > diff --git a/drivers/opp/debugfs.c b/drivers/opp/debugfs.c > index 596c185b5dda..a4476985e4ce 100644 > --- a/drivers/opp/debugfs.c > +++ b/drivers/opp/debugfs.c > @@ -187,14 +187,19 @@ 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; > + } > + > + if (!new_dev) > + return; I think you missed this check in the parent function ? if (!list_is_singular(&opp_table->dev_list)) { i.e. this bug can never happen.
diff --git a/drivers/opp/debugfs.c b/drivers/opp/debugfs.c index 596c185b5dda..a4476985e4ce 100644 --- a/drivers/opp/debugfs.c +++ b/drivers/opp/debugfs.c @@ -187,14 +187,19 @@ 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; + } + + if (!new_dev) + return; /* new_dev is guaranteed to be valid here */ dev = new_dev->dev;
The bug is here: dev = new_dev->dev; The list iterator 'new_dev' will point to a bogus position containing HEAD if the list is empty or no element is found. This case must be checked before any use of the iterator, otherwise it will lead to a invalid memory access. To fix this bug, add an check. 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 element. Cc: stable@vger.kernel.org Fixes: deaa51465105a ("PM / OPP: Add debugfs support") Signed-off-by: Xiaomeng Tong <xiam0nd.tong@gmail.com> --- drivers/opp/debugfs.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-)