On Mon, Feb 15, 2021 at 09:44:24AM +0100, Michal Hocko wrote:
> On Sat 13-02-21 15:05:28, Ivan Safonov wrote:
> > memdup_user() is shorter and safer equivalent
> > of kmalloc/copy_from_user pair.
> >
> > Signed-off-by: Ivan Safonov <insafo...@gmail.com>
> > ---
> > drivers/staging/wlan-ng/p80211netdev.c | 28 ++++++++++++--------------
> > 1 file changed, 13 insertions(+), 15 deletions(-)
> >
> > diff --git a/drivers/staging/wlan-ng/p80211netdev.c
> > b/drivers/staging/wlan-ng/p80211netdev.c
> > index a15abb2c8f54..6f9666dc0277 100644
> > --- a/drivers/staging/wlan-ng/p80211netdev.c
> > +++ b/drivers/staging/wlan-ng/p80211netdev.c
> > @@ -569,24 +569,22 @@ static int p80211knetdev_do_ioctl(struct net_device
> > *dev,
> > goto bail;
> > }
> >
> > - /* Allocate a buf of size req->len */
> > - msgbuf = kmalloc(req->len, GFP_KERNEL);
> > - if (msgbuf) {
> > - if (copy_from_user(msgbuf, (void __user *)req->data, req->len))
> > - result = -EFAULT;
> > - else
> > - result = p80211req_dorequest(wlandev, msgbuf);
> > + msgbuf = memdup_user(req->data, req->len);
>
> Move to memdup_user is definitely a right step. What is the range of
> req->len though? If this can be larger than PAGE_SIZE then vmemdup_user
> would be a better alternative.
req->len shoudn't be anywhere close to PAGE_SIZE but it's actually
important to check req->len and this code does not do that which leads
to memory corruption:
drivers/staging/wlan-ng/p80211netdev.c
566 goto bail;
567 } else if (cmd != P80211_IFREQ) {
568 result = -EINVAL;
569 goto bail;
570 }
571
572 msgbuf = memdup_user(req->data, req->len);
573 if (IS_ERR(msgbuf)) {
574 result = PTR_ERR(msgbuf);
575 goto bail;
576 }
577
578 result = p80211req_dorequest(wlandev, msgbuf);
We don't know that "req->len" is >= sizeof(*msgbuf), and then we pass
msgbuf top80211req_dorequest() which calls p80211req_handlemsg(). In
p80211req_handlemsg() then "req->len" has to be larger than
sizeof(struct p80211msg_lnxreq_hostwep).
579
580 if (result == 0) {
581 if (copy_to_user
582 ((void __user *)req->data, msgbuf, req->len)) {
583 result = -EFAULT;
584 }
585 }
586 kfree(msgbuf);
587
588 bail:
589 /* If allocate,copyfrom or copyto fails, return errno */
590 return result;
591 }
Smatch has a problem parsing this code because struct ifreq *ifr is a
union and Smatch gets confused. :/
regards,
dan carpenter
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