2020-09-03 14:52:46

by Tom Rix

Subject: [PATCH] media: em28xx: fix function pointer check

From: Tom Rix <[email protected]>

clang static analyzer reports this problem

em28xx-core.c:1162:4: warning: Called function pointer
is null (null dereference)
ops->suspend(dev->dev_next);
^~~~~~~~~~~~~~~~~~~~~~~~~~~

This is the problem block

if (ops->suspend)
ops->suspend(dev);
if (dev->dev_next)
ops->suspend(dev->dev_next);

The check for ops->suspend only covers one statement.
So fix the check consistent with other similar in
the file.

Change a similar check in em28xx_resume_extension()
to use consistent logic as its siblings.

Fixes: be7fd3c3a8c5 ("media: em28xx: Hauppauge DualHD second tuner functionality")
Signed-off-by: Tom Rix <[email protected]>
---
drivers/media/usb/em28xx/em28xx-core.c | 17 +++++++++--------
1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/drivers/media/usb/em28xx/em28xx-core.c b/drivers/media/usb/em28xx/em28xx-core.c
index e6088b5d1b80..d60f4c2a661d 100644
--- a/drivers/media/usb/em28xx/em28xx-core.c
+++ b/drivers/media/usb/em28xx/em28xx-core.c
@@ -1156,10 +1156,11 @@ int em28xx_suspend_extension(struct em28xx *dev)
dev_info(&dev->intf->dev, "Suspending extensions\n");
mutex_lock(&em28xx_devlist_mutex);
list_for_each_entry(ops, &em28xx_extension_devlist, next) {
- if (ops->suspend)
+ if (ops->suspend) {
ops->suspend(dev);
- if (dev->dev_next)
- ops->suspend(dev->dev_next);
+ if (dev->dev_next)
+ ops->suspend(dev->dev_next);
+ }
}
mutex_unlock(&em28xx_devlist_mutex);
return 0;
@@ -1172,11 +1173,11 @@ int em28xx_resume_extension(struct em28xx *dev)
dev_info(&dev->intf->dev, "Resuming extensions\n");
mutex_lock(&em28xx_devlist_mutex);
list_for_each_entry(ops, &em28xx_extension_devlist, next) {
- if (!ops->resume)
- continue;
- ops->resume(dev);
- if (dev->dev_next)
- ops->resume(dev->dev_next);
+ if (ops->resume) {
+ ops->resume(dev);
+ if (dev->dev_next)
+ ops->resume(dev->dev_next);
+ }
}
mutex_unlock(&em28xx_devlist_mutex);
return 0;
--
2.18.1

2020-09-03 16:56:06

by Nathan Chancellor

Subject: Re: [PATCH] media: em28xx: fix function pointer check

On Thu, Sep 03, 2020 at 07:50:38AM -0700, [email protected] wrote:
> From: Tom Rix <[email protected]>
>
> clang static analyzer reports this problem
>
> em28xx-core.c:1162:4: warning: Called function pointer
> is null (null dereference)
> ops->suspend(dev->dev_next);
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> This is the problem block
>
> if (ops->suspend)
> ops->suspend(dev);
> if (dev->dev_next)
> ops->suspend(dev->dev_next);
>
> The check for ops->suspend only covers one statement.
> So fix the check consistent with other similar in
> the file.
>
> Change a similar check in em28xx_resume_extension()
> to use consistent logic as its siblings.
>
> Fixes: be7fd3c3a8c5 ("media: em28xx: Hauppauge DualHD second tuner functionality")
> Signed-off-by: Tom Rix <[email protected]>

Seems reasonable.

Reviewed-by: Nathan Chancellor <[email protected]>

> ---
> drivers/media/usb/em28xx/em28xx-core.c | 17 +++++++++--------
> 1 file changed, 9 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/media/usb/em28xx/em28xx-core.c b/drivers/media/usb/em28xx/em28xx-core.c
> index e6088b5d1b80..d60f4c2a661d 100644
> --- a/drivers/media/usb/em28xx/em28xx-core.c
> +++ b/drivers/media/usb/em28xx/em28xx-core.c
> @@ -1156,10 +1156,11 @@ int em28xx_suspend_extension(struct em28xx *dev)
> dev_info(&dev->intf->dev, "Suspending extensions\n");
> mutex_lock(&em28xx_devlist_mutex);
> list_for_each_entry(ops, &em28xx_extension_devlist, next) {
> - if (ops->suspend)
> + if (ops->suspend) {
> ops->suspend(dev);
> - if (dev->dev_next)
> - ops->suspend(dev->dev_next);
> + if (dev->dev_next)
> + ops->suspend(dev->dev_next);
> + }
> }
> mutex_unlock(&em28xx_devlist_mutex);
> return 0;
> @@ -1172,11 +1173,11 @@ int em28xx_resume_extension(struct em28xx *dev)
> dev_info(&dev->intf->dev, "Resuming extensions\n");
> mutex_lock(&em28xx_devlist_mutex);
> list_for_each_entry(ops, &em28xx_extension_devlist, next) {
> - if (!ops->resume)
> - continue;
> - ops->resume(dev);
> - if (dev->dev_next)
> - ops->resume(dev->dev_next);
> + if (ops->resume) {
> + ops->resume(dev);
> + if (dev->dev_next)
> + ops->resume(dev->dev_next);
> + }
> }
> mutex_unlock(&em28xx_devlist_mutex);
> return 0;
> --
> 2.18.1
>

2020-09-09 17:22:48

by Hans Verkuil

Subject: Re: [PATCH] media: em28xx: fix function pointer check

On 03/09/2020 16:50, [email protected] wrote:
> From: Tom Rix <[email protected]>
>
> clang static analyzer reports this problem
>
> em28xx-core.c:1162:4: warning: Called function pointer
> is null (null dereference)
> ops->suspend(dev->dev_next);
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> This is the problem block
>
> if (ops->suspend)
> ops->suspend(dev);
> if (dev->dev_next)
> ops->suspend(dev->dev_next);
>
> The check for ops->suspend only covers one statement.
> So fix the check consistent with other similar in
> the file.
>
> Change a similar check in em28xx_resume_extension()
> to use consistent logic as its siblings.
>
> Fixes: be7fd3c3a8c5 ("media: em28xx: Hauppauge DualHD second tuner functionality")
> Signed-off-by: Tom Rix <[email protected]>
> ---
> drivers/media/usb/em28xx/em28xx-core.c | 17 +++++++++--------
> 1 file changed, 9 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/media/usb/em28xx/em28xx-core.c b/drivers/media/usb/em28xx/em28xx-core.c
> index e6088b5d1b80..d60f4c2a661d 100644
> --- a/drivers/media/usb/em28xx/em28xx-core.c
> +++ b/drivers/media/usb/em28xx/em28xx-core.c
> @@ -1156,10 +1156,11 @@ int em28xx_suspend_extension(struct em28xx *dev)
> dev_info(&dev->intf->dev, "Suspending extensions\n");
> mutex_lock(&em28xx_devlist_mutex);
> list_for_each_entry(ops, &em28xx_extension_devlist, next) {
> - if (ops->suspend)
> + if (ops->suspend) {
> ops->suspend(dev);
> - if (dev->dev_next)
> - ops->suspend(dev->dev_next);
> + if (dev->dev_next)
> + ops->suspend(dev->dev_next);
> + }
> }
> mutex_unlock(&em28xx_devlist_mutex);
> return 0;
> @@ -1172,11 +1173,11 @@ int em28xx_resume_extension(struct em28xx *dev)
> dev_info(&dev->intf->dev, "Resuming extensions\n");
> mutex_lock(&em28xx_devlist_mutex);
> list_for_each_entry(ops, &em28xx_extension_devlist, next) {
> - if (!ops->resume)
> - continue;

Actually, this code is fine: if !ops->resume, then just continue.

So there is no need to change this resume code.

And in fact, I think it would be best if the same approach was used in
em28xx_suspend_extension.

Regards,

Hans

> - ops->resume(dev);
> - if (dev->dev_next)
> - ops->resume(dev->dev_next);
> + if (ops->resume) {
> + ops->resume(dev);
> + if (dev->dev_next)
> + ops->resume(dev->dev_next);
> + }
> }
> mutex_unlock(&em28xx_devlist_mutex);
> return 0;
>