[PATCH v2 net 1/2] net: hamradio: bpqether: validate frame length in bpq_rcv()

[PATCH v2 net 1/2] net: hamradio: bpqether: validate frame length in bpq_rcv()

[Mashiro Chen]

The BPQ length field is decoded as:

  len = skb->data[0] + skb->data[1] * 256 - 5;

If the sender sets bytes [0..1] to values whose combined value is
less than 5, len becomes negative.  Passing a negative int to
skb_trim() silently converts to a huge unsigned value, causing the
function to be a no-op.  The frame is then passed up to AX.25 with
its original (untrimmed) payload, delivering garbage beyond the
declared frame boundary.

Additionally, a negative len corrupts the 64-bit rx_bytes counter
through implicit sign-extension.

Add a bounds check before pulling the length bytes: reject frames
where len is negative or exceeds the remaining skb data.

Cc: stable@vger.kernel.org
Cc: linux-hams@vger.kernel.org
Acked-by: Joerg Reuter <jreuter@yaina.de>
Signed-off-by: Mashiro Chen <mashiro.chen@mailbox.org>
---
 drivers/net/hamradio/bpqether.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/hamradio/bpqether.c b/drivers/net/hamradio/bpqether.c
index 045c5177262eaf..214fd1f819a1bb 100644
--- a/drivers/net/hamradio/bpqether.c
+++ b/drivers/net/hamradio/bpqether.c
@@ -187,6 +187,9 @@ static int bpq_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_ty
 
 	len = skb->data[0] + skb->data[1] * 256 - 5;
 
+	if (len < 0 || len > skb->len - 2)
+		goto drop_unlock;
+
 	skb_pull(skb, 2);	/* Remove the length bytes */
 	skb_trim(skb, len);	/* Set the length of the data */
 
-- 
2.53.0

[PATCH v2 net 2/2] net: hamradio: scc: validate bufsize in SIOCSCCSMEM ioctl

[Mashiro Chen]

The SIOCSCCSMEM ioctl copies a scc_mem_config from user space and
assigns its bufsize field directly to scc->stat.bufsize without any
range validation:

  scc->stat.bufsize = memcfg.bufsize;

If a privileged user (CAP_SYS_RAWIO) sets bufsize to 0, the receive
interrupt handler later calls dev_alloc_skb(0) and immediately writes
a KISS type byte via skb_put_u8() into a zero-capacity socket buffer,
corrupting the adjacent skb_shared_info region.

Reject bufsize values smaller than 16; this is large enough to hold
at least one KISS header byte plus useful data.

Cc: stable@vger.kernel.org
Cc: linux-hams@vger.kernel.org
Signed-off-by: Mashiro Chen <mashiro.chen@mailbox.org>
---
 drivers/net/hamradio/scc.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/hamradio/scc.c b/drivers/net/hamradio/scc.c
index ae5048efde686a..8569db4a71401c 100644
--- a/drivers/net/hamradio/scc.c
+++ b/drivers/net/hamradio/scc.c
@@ -1909,6 +1909,8 @@ static int scc_net_siocdevprivate(struct net_device *dev,
 			if (!capable(CAP_SYS_RAWIO)) return -EPERM;
 			if (!arg || copy_from_user(&memcfg, arg, sizeof(memcfg)))
 				return -EINVAL;
+			if (memcfg.bufsize < 16)
+				return -EINVAL;
 			scc->stat.bufsize   = memcfg.bufsize;
 			return 0;
 		
-- 
2.53.0

Re: [PATCH v2 net 2/2] net: hamradio: scc: validate bufsize in SIOCSCCSMEM ioctl

[Joerg Reuter]

Looks great, thanks!

    73, Joerg

> The SIOCSCCSMEM ioctl copies a scc_mem_config from user space and
> assigns its bufsize field directly to scc->stat.bufsize without any
> range validation:
> 
>   scc->stat.bufsize = memcfg.bufsize;
> 
> If a privileged user (CAP_SYS_RAWIO) sets bufsize to 0, the receive
> interrupt handler later calls dev_alloc_skb(0) and immediately writes
> a KISS type byte via skb_put_u8() into a zero-capacity socket buffer,
> corrupting the adjacent skb_shared_info region.
> 
> Reject bufsize values smaller than 16; this is large enough to hold
> at least one KISS header byte plus useful data.
> 
> Cc: stable@vger.kernel.org
> Cc: linux-hams@vger.kernel.org
Acked-by: Joerg Reuter <jreuter@yaina.de>
> Signed-off-by: Mashiro Chen <mashiro.chen@mailbox.org>
> ---
>  drivers/net/hamradio/scc.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/net/hamradio/scc.c b/drivers/net/hamradio/scc.c
> index ae5048efde686a..8569db4a71401c 100644
> --- a/drivers/net/hamradio/scc.c
> +++ b/drivers/net/hamradio/scc.c
> @@ -1909,6 +1909,8 @@ static int scc_net_siocdevprivate(struct net_device *dev,
>  			if (!capable(CAP_SYS_RAWIO)) return -EPERM;
>  			if (!arg || copy_from_user(&memcfg, arg, sizeof(memcfg)))
>  				return -EINVAL;
> +			if (memcfg.bufsize < 16)
> +				return -EINVAL;
>  			scc->stat.bufsize   = memcfg.bufsize;
>  			return 0;
>  		
> -- 
> 2.53.0
> 

-- 
Joerg Reuter                                    http://yaina.de/jreuter
And I make my way to where the warm scent of soil fills the evening air. 
Everything is waiting quietly out there....                 (Anne Clark)