2021-11-03 16:16:27

by butt3rflyh4ck

[permalink] [raw]

Subject: A kernel-infoleak bug in pppoe_getname() in drivers/net/ppp/pppoe.c

---

Hi, I report a kernel-infoleak bug in pppoe_getname()) in
drivers/net/ppp/pppoe.c.
And we can call getname ioctl to invoke pppoe_getname().

###anaylze
```
static int pppoe_getname(struct socket *sock, struct sockaddr *uaddr,
int peer)
{
int len = sizeof(struct sockaddr_pppox);
struct sockaddr_pppox sp; ///---> define a 'sp' in stack but does
not clear it

sp.sa_family = AF_PPPOX; ///---> sp.sa_family is a short type, just
2 byte sizes.
sp.sa_protocol = PX_PROTO_OE;
memcpy(&sp.sa_addr.pppoe, &pppox_sk(sock->sk)->pppoe_pa,
sizeof(struct pppoe_addr));

memcpy(uaddr, &sp, len);

return len;
}
```
There is an anonymous 2-byte hole after sa_family, make sure to clear it.

###fix
use memset() to clear the struct sockaddr_pppox sp.
```
diff --git a/drivers/net/ppp/pppoe.c b/drivers/net/ppp/pppoe.c
index 3619520340b7..fec328ad7202 100644
--- a/drivers/net/ppp/pppoe.c
+++ b/drivers/net/ppp/pppoe.c
@@ -723,6 +723,11 @@ static int pppoe_getname(struct socket *sock,
struct sockaddr *uaddr,
int len = sizeof(struct sockaddr_pppox);
struct sockaddr_pppox sp;

+ /* There is an anonymous 2-byte hole after sa_family,
+ * make sure to clear it.
+ */
+ memset(&sp, 0, len);
+
sp.sa_family = AF_PPPOX;
sp.sa_protocol = PX_PROTO_OE;
memcpy(&sp.sa_addr.pppoe, &pppox_sk(sock->sk)->pppoe_pa,
```
The attachment is a patch.


Regards,
butt3rflyh4ck.
--
Active Defense Lab of Venustech

---

Attachments:

0001-net-ppp-pppoe-fix-a-kernel-infoleak-in-pppoe_getname.patch (1.05 kB)

2021-11-03 16:57:32

by Jakub Kicinski

[permalink] [raw]

Subject: Re: A kernel-infoleak bug in pppoe_getname() in drivers/net/ppp/pppoe.c

---

On Thu, 4 Nov 2021 00:14:31 +0800 butt3rflyh4ck wrote:
> Hi, I report a kernel-infoleak bug in pppoe_getname()) in
> drivers/net/ppp/pppoe.c.
> And we can call getname ioctl to invoke pppoe_getname().
>
> ###anaylze
> ```
> static int pppoe_getname(struct socket *sock, struct sockaddr *uaddr,
> int peer)
> {
> int len = sizeof(struct sockaddr_pppox);
> struct sockaddr_pppox sp; ///---> define a 'sp' in stack but does
> not clear it
>
> sp.sa_family = AF_PPPOX; ///---> sp.sa_family is a short type, just

But the structure is marked as __packed.

> 2 byte sizes.
> sp.sa_protocol = PX_PROTO_OE;
> memcpy(&sp.sa_addr.pppoe, &pppox_sk(sock->sk)->pppoe_pa,
> sizeof(struct pppoe_addr));
>
> memcpy(uaddr, &sp, len);
>
> return len;
> }
> ```
> There is an anonymous 2-byte hole after sa_family, make sure to clear it.
>
> ###fix
> use memset() to clear the struct sockaddr_pppox sp.
> ```
> diff --git a/drivers/net/ppp/pppoe.c b/drivers/net/ppp/pppoe.c
> index 3619520340b7..fec328ad7202 100644
> --- a/drivers/net/ppp/pppoe.c
> +++ b/drivers/net/ppp/pppoe.c
> @@ -723,6 +723,11 @@ static int pppoe_getname(struct socket *sock,
> struct sockaddr *uaddr,
> int len = sizeof(struct sockaddr_pppox);
> struct sockaddr_pppox sp;
>
> + /* There is an anonymous 2-byte hole after sa_family,
> + * make sure to clear it.
> + */
> + memset(&sp, 0, len);
> +
> sp.sa_family = AF_PPPOX;
> sp.sa_protocol = PX_PROTO_OE;
> memcpy(&sp.sa_addr.pppoe, &pppox_sk(sock->sk)->pppoe_pa,
> ```
> The attachment is a patch.

2021-11-04 03:11:23

by butt3rflyh4ck

[permalink] [raw]

Subject: Re: A kernel-infoleak bug in pppoe_getname() in drivers/net/ppp/pppoe.c

---

Ok, I will check. Oh, you are right.



On Thu, Nov 4, 2021 at 12:53 AM Jakub Kicinski <[email protected]> wrote:
>
> On Thu, 4 Nov 2021 00:14:31 +0800 butt3rflyh4ck wrote:
> > Hi, I report a kernel-infoleak bug in pppoe_getname()) in
> > drivers/net/ppp/pppoe.c.
> > And we can call getname ioctl to invoke pppoe_getname().
> >
> > ###anaylze
> > ```
> > static int pppoe_getname(struct socket *sock, struct sockaddr *uaddr,
> > int peer)
> > {
> > int len = sizeof(struct sockaddr_pppox);
> > struct sockaddr_pppox sp; ///---> define a 'sp' in stack but does
> > not clear it
> >
> > sp.sa_family = AF_PPPOX; ///---> sp.sa_family is a short type, just
>
> But the structure is marked as __packed.
>
> > 2 byte sizes.
> > sp.sa_protocol = PX_PROTO_OE;
> > memcpy(&sp.sa_addr.pppoe, &pppox_sk(sock->sk)->pppoe_pa,
> > sizeof(struct pppoe_addr));
> >
> > memcpy(uaddr, &sp, len);
> >
> > return len;
> > }
> > ```
> > There is an anonymous 2-byte hole after sa_family, make sure to clear it.
> >
> > ###fix
> > use memset() to clear the struct sockaddr_pppox sp.
> > ```
> > diff --git a/drivers/net/ppp/pppoe.c b/drivers/net/ppp/pppoe.c
> > index 3619520340b7..fec328ad7202 100644
> > --- a/drivers/net/ppp/pppoe.c
> > +++ b/drivers/net/ppp/pppoe.c
> > @@ -723,6 +723,11 @@ static int pppoe_getname(struct socket *sock,
> > struct sockaddr *uaddr,
> > int len = sizeof(struct sockaddr_pppox);
> > struct sockaddr_pppox sp;
> >
> > + /* There is an anonymous 2-byte hole after sa_family,
> > + * make sure to clear it.
> > + */
> > + memset(&sp, 0, len);
> > +
> > sp.sa_family = AF_PPPOX;
> > sp.sa_protocol = PX_PROTO_OE;
> > memcpy(&sp.sa_addr.pppoe, &pppox_sk(sock->sk)->pppoe_pa,
> > ```
> > The attachment is a patch.
>


--
Active Defense Lab of Venustech