2021-02-13 13:19:56

by Ivan Safonov

Subject: [PATCH] staging:wlan-ng: use memdup_user instead of kmalloc/copy_from_user

memdup_user() is shorter and safer equivalent
of kmalloc/copy_from_user pair.

Signed-off-by: Ivan Safonov <[email protected]>
---
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);
+ if (IS_ERR(msgbuf)) {
+ result = PTR_ERR(msgbuf);
+ goto bail;
+ }

- if (result == 0) {
- if (copy_to_user
- ((void __user *)req->data, msgbuf, req->len)) {
- result = -EFAULT;
- }
+ result = p80211req_dorequest(wlandev, msgbuf);
+
+ if (result == 0) {
+ if (copy_to_user
+ ((void __user *)req->data, msgbuf, req->len)) {
+ result = -EFAULT;
}
- kfree(msgbuf);
- } else {
- result = -ENOMEM;
}
+ kfree(msgbuf);
+
bail:
/* If allocate,copyfrom or copyto fails, return errno */
return result;
--
2.26.2

2021-02-15 08:47:32

by Michal Hocko

Subject: Re: [PATCH] staging:wlan-ng: use memdup_user instead of kmalloc/copy_from_user

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 <[email protected]>
> ---
> 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.

--
Michal Hocko
SUSE Labs

2021-02-15 13:29:55

by Dan Carpenter

Subject: Re: [PATCH] staging:wlan-ng: use memdup_user instead of kmalloc/copy_from_user

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 <[email protected]>
> > ---
> > 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