* [PATCH v2] opp: use list iterator only inside the loop
@ 2022-03-31 2:36 Xiaomeng Tong
2022-03-31 2:49 ` Viresh Kumar
0 siblings, 1 reply; 6+ messages in thread
From: Xiaomeng Tong @ 2022-03-31 2:36 UTC (permalink / raw)
To: vireshk, nm, sboyd; +Cc: linux-pm, linux-kernel, Xiaomeng Tong
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
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH v2] opp: use list iterator only inside the loop
2022-03-31 2:36 [PATCH v2] opp: use list iterator only inside the loop Xiaomeng Tong
@ 2022-03-31 2:49 ` Viresh Kumar
0 siblings, 0 replies; 6+ messages in thread
From: Viresh Kumar @ 2022-03-31 2:49 UTC (permalink / raw)
To: Xiaomeng Tong; +Cc: vireshk, nm, sboyd, linux-pm, linux-kernel
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
--
viresh
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH v2] opp: use list iterator only inside the loop
@ 2022-03-31 8:30 Xiaomeng Tong
2022-03-31 8:44 ` Viresh Kumar
2022-04-11 3:02 ` Viresh Kumar
0 siblings, 2 replies; 6+ messages in thread
From: Xiaomeng Tong @ 2022-03-31 8:30 UTC (permalink / raw)
To: vireshk, nm, sboyd; +Cc: linux-pm, linux-kernel, Xiaomeng Tong
To move the list iterator variable into the list_for_each_entry_*()
macro in the future it should be avoided to use the list iterator
variable after the loop body.
To *never* use the list iterator variable after the loop it was
concluded to use a separate dedicated pointer variable [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://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/
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
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH v2] opp: use list iterator only inside the loop
2022-03-31 8:30 Xiaomeng Tong
@ 2022-03-31 8:44 ` Viresh Kumar
2022-03-31 8:51 ` Xiaomeng Tong
2022-04-11 3:02 ` Viresh Kumar
1 sibling, 1 reply; 6+ messages in thread
From: Viresh Kumar @ 2022-03-31 8:44 UTC (permalink / raw)
To: Xiaomeng Tong; +Cc: vireshk, nm, sboyd, linux-pm, linux-kernel
This is V3 and not V2. You need to be careful to update them for every
single version of patch you send.
On 31-03-22, 16:30, Xiaomeng Tong wrote:
> To move the list iterator variable into the list_for_each_entry_*()
> macro in the future it should be avoided to use the list iterator
> variable after the loop body.
>
> To *never* use the list iterator variable after the loop it was
> concluded to use a separate dedicated pointer variable [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://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/
>
> 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(-)
Looks good now. I will apply it in few days.
--
viresh
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v2] opp: use list iterator only inside the loop
2022-03-31 8:44 ` Viresh Kumar
@ 2022-03-31 8:51 ` Xiaomeng Tong
0 siblings, 0 replies; 6+ messages in thread
From: Xiaomeng Tong @ 2022-03-31 8:51 UTC (permalink / raw)
To: viresh.kumar; +Cc: linux-kernel, linux-pm, nm, sboyd, vireshk, xiam0nd.tong
On Thu, 31 Mar 2022 14:14:53 +0530, Viresh Kumar wrote:
> This is V3 and not V2. You need to be careful to update them for every
> single version of patch you send.
>
Thank you very much for your patient reply. I got it.
--
Xiaomeng Tong
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v2] opp: use list iterator only inside the loop
2022-03-31 8:30 Xiaomeng Tong
2022-03-31 8:44 ` Viresh Kumar
@ 2022-04-11 3:02 ` Viresh Kumar
1 sibling, 0 replies; 6+ messages in thread
From: Viresh Kumar @ 2022-04-11 3:02 UTC (permalink / raw)
To: Xiaomeng Tong; +Cc: vireshk, nm, sboyd, linux-pm, linux-kernel
On 31-03-22, 16:30, Xiaomeng Tong wrote:
> To move the list iterator variable into the list_for_each_entry_*()
> macro in the future it should be avoided to use the list iterator
> variable after the loop body.
>
> To *never* use the list iterator variable after the loop it was
> concluded to use a separate dedicated pointer variable [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://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/
>
> Signed-off-by: Xiaomeng Tong <xiam0nd.tong@gmail.com>
> ---
Applied. Thanks.
--
viresh
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2022-04-11 3:02 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2022-03-31 2:36 [PATCH v2] opp: use list iterator only inside the loop Xiaomeng Tong
2022-03-31 2:49 ` Viresh Kumar
2022-03-31 8:30 Xiaomeng Tong
2022-03-31 8:44 ` Viresh Kumar
2022-03-31 8:51 ` Xiaomeng Tong
2022-04-11 3:02 ` Viresh Kumar
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