diff mbox series

mac80211_hwsim: correctly handle zero length frames

Message ID 20210610161916.9307-1-mail@anirudhrb.com
State New
Headers show
Series mac80211_hwsim: correctly handle zero length frames | expand

Commit Message

Anirudh Rayabharam June 10, 2021, 4:19 p.m. UTC 
syzbot, using KMSAN, has reported an uninit-value access in
hwsim_cloned_frame_received_nl(). This is happening because frame_data_len
is 0. The code doesn't detect this case and blindly tries to read the
frame's header.

Fix this by bailing out in case frame_data_len is 0.

Reported-by: syzbot+b2645b5bf1512b81fa22@syzkaller.appspotmail.com
Tested-by: syzbot+b2645b5bf1512b81fa22@syzkaller.appspotmail.com
Signed-off-by: Anirudh Rayabharam <mail@anirudhrb.com>
---
 drivers/net/wireless/mac80211_hwsim.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Johannes Berg June 18, 2021, 9:36 a.m. UTC | #1 
On Thu, 2021-06-10 at 21:49 +0530, Anirudh Rayabharam wrote:
> syzbot, using KMSAN, has reported an uninit-value access in

> hwsim_cloned_frame_received_nl(). This is happening because frame_data_len

> is 0. The code doesn't detect this case and blindly tries to read the

> frame's header.

> 

> Fix this by bailing out in case frame_data_len is 0.


This really seems quite pointless - you should bail out if the frame is
too short for what we need to do, not just when it's 0.

johannes
Anirudh Rayabharam June 23, 2021, 7:26 a.m. UTC | #2 
On Fri, Jun 18, 2021 at 11:36:16AM +0200, Johannes Berg wrote:
> On Thu, 2021-06-10 at 21:49 +0530, Anirudh Rayabharam wrote:

> > syzbot, using KMSAN, has reported an uninit-value access in

> > hwsim_cloned_frame_received_nl(). This is happening because frame_data_len

> > is 0. The code doesn't detect this case and blindly tries to read the

> > frame's header.

> > 

> > Fix this by bailing out in case frame_data_len is 0.

> 

> This really seems quite pointless - you should bail out if the frame is

> too short for what we need to do, not just when it's 0.


That makes sense. Do you happen to know what the min length of a valid
frame is? There doesn't seem to be constant defined for that already.

	- Anirudh

> 

> johannes

>
diff mbox series

Patch

diff --git a/drivers/net/wireless/mac80211_hwsim.c b/drivers/net/wireless/mac80211_hwsim.c
index 51ce767eaf88..ccfe40313109 100644
--- a/drivers/net/wireless/mac80211_hwsim.c
+++ b/drivers/net/wireless/mac80211_hwsim.c
@@ -3649,7 +3649,7 @@  static int hwsim_cloned_frame_received_nl(struct sk_buff *skb_2,
 	if (skb == NULL)
 		goto err;
 
-	if (frame_data_len > IEEE80211_MAX_DATA_LEN)
+	if (frame_data_len == 0 || frame_data_len > IEEE80211_MAX_DATA_LEN)
 		goto err;
 
 	/* Copy the data */