Re: [PATCH] staging: rtl8723bs: Fix two possible sleep-in-atomic-context bugs in translate_scan()

[Jia-Ju Bai]

On 2018/6/20 17:56, Dan Carpenter wrote:
> On Wed, Jun 20, 2018 at 05:50:16PM +0800, Jia-Ju Bai wrote:
> > The driver may sleep with holding a spinlock.
> > The function call paths (from bottom to top) in Linux-4.16.7 are:
> >
> > [FUNC] kzalloc(GFP_KERNEL)
> > drivers/staging/rtl8723bs/os_dep/ioctl_linux.c, 323:
> > 		kzalloc in translate_scan
> > drivers/staging/rtl8723bs/os_dep/ioctl_linux.c, 1554:
> > 		translate_scan in rtw_wx_get_scan
> > drivers/staging/rtl8723bs/os_dep/ioctl_linux.c, 1533:
> > 		spin_lock_bh in rtw_wx_get_scan
> >
> > [FUNC] kzalloc(GFP_KERNEL)
> > drivers/staging/rtl8723bs/os_dep/ioctl_linux.c, 455:
> > 		kzalloc in translate_scan
> > drivers/staging/rtl8723bs/os_dep/ioctl_linux.c, 1554:
> > 		translate_scan in rtw_wx_get_scan
> > drivers/staging/rtl8723bs/os_dep/ioctl_linux.c, 1533:
> > 		spin_lock_bh in rtw_wx_get_scan
> >
> > To fix these bugs, GFP_KERNEL is replaced with GFP_ATOMIC.
> >
> > These bugs are found by my static analysis tool (DSAC-2) and checked by
> > my code review.
> >
> > Signed-off-by: Jia-Ju Bai <baijiaju1990@xxxxxxxxx>
> > ---
> >   drivers/staging/rtl8723bs/os_dep/ioctl_linux.c | 4 ++--
> >   1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/staging/rtl8723bs/os_dep/ioctl_linux.c b/drivers/staging/rtl8723bs/os_dep/ioctl_linux.c
> > index b26533983864..7632b8974563 100644
> > --- a/drivers/staging/rtl8723bs/os_dep/ioctl_linux.c
> > +++ b/drivers/staging/rtl8723bs/os_dep/ioctl_linux.c
> > @@ -321,7 +321,7 @@ static char *translate_scan(struct adapter *padapter,
> >   		RT_TRACE(_module_rtl871x_mlme_c_, _drv_info_, ("rtw_wx_get_scan: ssid =%s\n", pnetwork->network.Ssid.Ssid));
> >   		RT_TRACE(_module_rtl871x_mlme_c_, _drv_info_, ("rtw_wx_get_scan: wpa_len =%d rsn_len =%d\n", wpa_len, rsn_len));
> >   
> > -		buf = kzalloc(MAX_WPA_IE_LEN*2, GFP_KERNEL);
> > +		buf = kzalloc(MAX_WPA_IE_LEN*2, GFP_ATOMIC);
> >   		if (!buf)
> >   			return start;
> Thanks!  It occurs to me that another way to detect this bug is that
> one of the allocations in this function already uses GFP_ATOMIC.  It
> doesn't normally make sense to mix GFP_ATOMIC and GFP_KERNEL when there
> isn't any locking in the function.

Yes, this pattern is interesting for bug finding :)
But to fix the bugs of this pattern, we need to decide whether 
GFP_ATOMIC or GFP_KERNEL should be used here.


Best wishes,
Jia-Ju Bai