| Message ID | 20230417195003.19504-1-korotkov.maxim.s@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | usb: typec: fix potential NULL dereference | expand |
On Tue, Apr 18, 2023 at 09:56:51AM +0300, Maxim Korotkov wrote: > On 18.04.2023 09:16, Greg Kroah-Hartman wrote: > > On Mon, Apr 17, 2023 at 10:50:03PM +0300, Maxim Korotkov wrote: > > > The pointer 'adev' was being dereferenced before being checked for NULL > > > in the 'type_alt mode_enter()' and 'type_alt mode_exit()' functions. > > > Although this is a hypothetical issue, it's better to move the pointer > > > assignment after the NULL check to avoid any potential problems. > > > > > > Found by Linux Verification Center with Svace static analyzer. > > > > > > Fixes: 8a37d87d72f0 ("usb: typec: Bus type for alternate modes") > > > Signed-off-by: Maxim Korotkov <korotkov.maxim.s@gmail.com> > > > --- > > > drivers/usb/typec/bus.c | 13 +++++++++---- > > > 1 file changed, 9 insertions(+), 4 deletions(-) > > > > > > diff --git a/drivers/usb/typec/bus.c b/drivers/usb/typec/bus.c > > > index 098f0efaa58d..ae0aca8f33db 100644 > > > --- a/drivers/usb/typec/bus.c > > > +++ b/drivers/usb/typec/bus.c > > > @@ -125,13 +125,16 @@ EXPORT_SYMBOL_GPL(typec_altmode_notify); > > > */ > > > int typec_altmode_enter(struct typec_altmode *adev, u32 *vdo) > > > { > > > - struct altmode *partner = to_altmode(adev)->partner; > > > - struct typec_altmode *pdev = &partner->adev; > > > + struct altmode *partner; > > > + struct typec_altmode *pdev; > > > int ret; > > > if (!adev || adev->active) > > > return 0; > > > + partner = to_altmode(adev)->partner; > > > + pdev = &partner->adev; > > > > As you point out, the original code is still fine here, we check before > > we actually use these values. > > > > Also, can adev every actually be NULL? In looking at the code paths, I > > can't see how that could happen. > > > > thanks, > > > > greg k-h > > I agree that the adev will most likely never be NULL, but usually this > pointer is checked before usage (for example in typec_altmode_notify() or > typec_altmode_vdm()). It is a little odd that in these functions it utilized > before check. Is it just extra check that can be removed? Please go ahead and remove it. thanks,
diff --git a/drivers/usb/typec/bus.c b/drivers/usb/typec/bus.c index 098f0efaa58d..ae0aca8f33db 100644 --- a/drivers/usb/typec/bus.c +++ b/drivers/usb/typec/bus.c @@ -125,13 +125,16 @@ EXPORT_SYMBOL_GPL(typec_altmode_notify); */ int typec_altmode_enter(struct typec_altmode *adev, u32 *vdo) { - struct altmode *partner = to_altmode(adev)->partner; - struct typec_altmode *pdev = &partner->adev; + struct altmode *partner; + struct typec_altmode *pdev; int ret; if (!adev || adev->active) return 0; + partner = to_altmode(adev)->partner; + pdev = &partner->adev; + if (!pdev->ops || !pdev->ops->enter) return -EOPNOTSUPP; @@ -156,13 +159,15 @@ EXPORT_SYMBOL_GPL(typec_altmode_enter); */ int typec_altmode_exit(struct typec_altmode *adev) { - struct altmode *partner = to_altmode(adev)->partner; - struct typec_altmode *pdev = &partner->adev; + struct altmode *partner; + struct typec_altmode *pdev; int ret; if (!adev || !adev->active) return 0; + partner = to_altmode(adev)->partner; + pdev = &partner->adev; if (!pdev->ops || !pdev->ops->exit) return -EOPNOTSUPP;
The pointer 'adev' was being dereferenced before being checked for NULL in the 'type_alt mode_enter()' and 'type_alt mode_exit()' functions. Although this is a hypothetical issue, it's better to move the pointer assignment after the NULL check to avoid any potential problems. Found by Linux Verification Center with Svace static analyzer. Fixes: 8a37d87d72f0 ("usb: typec: Bus type for alternate modes") Signed-off-by: Maxim Korotkov <korotkov.maxim.s@gmail.com> --- drivers/usb/typec/bus.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-)