Messages in this thread | | | Date | Tue, 18 Apr 2023 09:56:51 +0300 | Subject | Re: [PATCH] usb: typec: fix potential NULL dereference | From | Maxim Korotkov <> |
| |
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?
best regards, Max
| |