diff mbox series

[Linux-kernel-mentees,v3,net] rose: Fix Null pointer dereference in rose_send_frame()

Message ID 20201107191835.5541-1-anmol.karan123@gmail.com
State Superseded
Headers show
Series [Linux-kernel-mentees,v3,net] rose: Fix Null pointer dereference in rose_send_frame() | expand

Commit Message

Anmol Karn Nov. 7, 2020, 7:18 p.m. UTC 
rose_send_frame() dereferences `neigh->dev` when called from
rose_transmit_clear_request(), and the first occurrence of the
`neigh` is in rose_loopback_timer() as `rose_loopback_neigh`,
and it is initialized in rose_add_loopback_neigh() as NULL.
i.e when `rose_loopback_neigh` used in rose_loopback_timer()
its `->dev` was still NULL and rose_loopback_timer() was calling
rose_rx_call_request() without checking for NULL.

- net/rose/rose_link.c
This bug seems to get triggered in this line:

rose_call = (ax25_address *)neigh->dev->dev_addr;

Fix it by adding NULL checking for `rose_loopback_neigh->dev`
in rose_loopback_timer().

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: syzbot+a1c743815982d9496393@syzkaller.appspotmail.com
Tested-by: syzbot+a1c743815982d9496393@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?id=9d2a7ca8c7f2e4b682c97578dfa3f236258300b3
Signed-off-by: Anmol Karn <anmol.karan123@gmail.com>
---
Changes in v3:
        - Corrected checkpatch warnings and errors (Suggested-by: Saeed Mahameed <saeed@kernel.org>)
	- Added "Fixes:" tag (Suggested-by: Saeed Mahameed <saeed@kernel.org>)
Changes in v2:
	- Added NULL check in rose_loopback_timer() (Suggested-by: Greg KH <gregkh@linuxfoundation.org>)

 net/rose/rose_loopback.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

-
2.29.2

Comments

Jakub Kicinski Nov. 10, 2020, 5:58 p.m. UTC | #1 
On Sun,  8 Nov 2020 00:48:35 +0530 Anmol Karn wrote:
> +			dev = rose_dev_get(dest);


this calls dev_hold internally, you never release that reference in
case ..neigh->dev is NULL

> +			if (rose_loopback_neigh->dev && dev) {
Anmol Karn Nov. 10, 2020, 7:45 p.m. UTC | #2 
Hello Sir,

On Tue, Nov 10, 2020 at 09:58:15AM -0800, Jakub Kicinski wrote:
> On Sun,  8 Nov 2020 00:48:35 +0530 Anmol Karn wrote:

> > +			dev = rose_dev_get(dest);

> 

> this calls dev_hold internally, you never release that reference in

> case ..neigh->dev is NULL

> 

> > +			if (rose_loopback_neigh->dev && dev) {


Ah, I missed to `dev_put()` the `dev` after checking for, if neigh->dev is NULL,
I will fix it soon and send another version.

Thank you for review.


Anmol
Jakub Kicinski Nov. 14, 2020, 7:18 p.m. UTC | #3 
On Wed, 11 Nov 2020 22:29:54 +0530 Anmol Karn wrote:
> rose_send_frame() dereferences `neigh->dev` when called from

> rose_transmit_clear_request(), and the first occurrence of the

> `neigh` is in rose_loopback_timer() as `rose_loopback_neigh`,

> and it is initialized in rose_add_loopback_neigh() as NULL.

> i.e when `rose_loopback_neigh` used in rose_loopback_timer()

> its `->dev` was still NULL and rose_loopback_timer() was calling

> rose_rx_call_request() without checking for NULL.

> 

> - net/rose/rose_link.c

> This bug seems to get triggered in this line:

> 

> rose_call = (ax25_address *)neigh->dev->dev_addr;

> 

> Fix it by adding NULL checking for `rose_loopback_neigh->dev`

> in rose_loopback_timer().

> 

> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")

> Reported-by: syzbot+a1c743815982d9496393@syzkaller.appspotmail.com

> Tested-by: syzbot+a1c743815982d9496393@syzkaller.appspotmail.com

> Link: https://syzkaller.appspot.com/bug?id=9d2a7ca8c7f2e4b682c97578dfa3f236258300b3

> Signed-off-by: Anmol Karn <anmol.karan123@gmail.com>


> diff --git a/net/rose/rose_loopback.c b/net/rose/rose_loopback.c

> index 7b094275ea8b..6a71b6947d92 100644

> --- a/net/rose/rose_loopback.c

> +++ b/net/rose/rose_loopback.c

> @@ -96,10 +96,12 @@ static void rose_loopback_timer(struct timer_list *unused)

>  		}

> 

>  		if (frametype == ROSE_CALL_REQUEST) {

> -			if ((dev = rose_dev_get(dest)) != NULL) {

> +			dev = rose_dev_get(dest);

> +			if (rose_loopback_neigh->dev && dev) {

>  				if (rose_rx_call_request(skb, dev, rose_loopback_neigh, lci_o) == 0)

>  					kfree_skb(skb);

>  			} else {

> +				dev_put(dev);

>  				kfree_skb(skb);

>  			}

>  		} else {


This is still not correct. With this code dev_put() could be called with
NULL, which would cause a crash.

There is also a dev_put() missing if rose_rx_call_request() returns 0.

I think that this is the correct code:

diff --git a/net/rose/rose_loopback.c b/net/rose/rose_loopback.c
index 7b094275ea8b..ff252ef73592 100644
--- a/net/rose/rose_loopback.c
+++ b/net/rose/rose_loopback.c
@@ -96,11 +96,22 @@ static void rose_loopback_timer(struct timer_list *unused)
 		}
 
 		if (frametype == ROSE_CALL_REQUEST) {
-			if ((dev = rose_dev_get(dest)) != NULL) {
-				if (rose_rx_call_request(skb, dev, rose_loopback_neigh, lci_o) == 0)
-					kfree_skb(skb);
-			} else {
+			if (!rose_loopback_neigh->dev) {
 				kfree_skb(skb);
+				continue;
+			}
+
+			dev = rose_dev_get(dest);
+			if (!dev) {
+				kfree_skb(skb);
+				continue;
+			}
+
+			if (rose_rx_call_request(skb, dev, rose_loopback_neigh,
+						 lci_o) == 0) {
+				dev_put(dev);
+				kfree_skb(skb);
 			}
 		} else {
 			kfree_skb(skb);

Please test this and resubmit it if it works.
Anmol Karn Nov. 15, 2020, 11:44 a.m. UTC | #4 
On Sat, Nov 14, 2020 at 11:18:38AM -0800, Jakub Kicinski wrote:
> On Wed, 11 Nov 2020 22:29:54 +0530 Anmol Karn wrote:

> > rose_send_frame() dereferences `neigh->dev` when called from

> > rose_transmit_clear_request(), and the first occurrence of the

> > `neigh` is in rose_loopback_timer() as `rose_loopback_neigh`,

> > and it is initialized in rose_add_loopback_neigh() as NULL.

> > i.e when `rose_loopback_neigh` used in rose_loopback_timer()

> > its `->dev` was still NULL and rose_loopback_timer() was calling

> > rose_rx_call_request() without checking for NULL.

> > 

> > - net/rose/rose_link.c

> > This bug seems to get triggered in this line:

> > 

> > rose_call = (ax25_address *)neigh->dev->dev_addr;

> > 

> > Fix it by adding NULL checking for `rose_loopback_neigh->dev`

> > in rose_loopback_timer().

> > 

> > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")

> > Reported-by: syzbot+a1c743815982d9496393@syzkaller.appspotmail.com

> > Tested-by: syzbot+a1c743815982d9496393@syzkaller.appspotmail.com

> > Link: https://syzkaller.appspot.com/bug?id=9d2a7ca8c7f2e4b682c97578dfa3f236258300b3

> > Signed-off-by: Anmol Karn <anmol.karan123@gmail.com>

> 

> > diff --git a/net/rose/rose_loopback.c b/net/rose/rose_loopback.c

> > index 7b094275ea8b..6a71b6947d92 100644

> > --- a/net/rose/rose_loopback.c

> > +++ b/net/rose/rose_loopback.c

> > @@ -96,10 +96,12 @@ static void rose_loopback_timer(struct timer_list *unused)

> >  		}

> > 

> >  		if (frametype == ROSE_CALL_REQUEST) {

> > -			if ((dev = rose_dev_get(dest)) != NULL) {

> > +			dev = rose_dev_get(dest);

> > +			if (rose_loopback_neigh->dev && dev) {

> >  				if (rose_rx_call_request(skb, dev, rose_loopback_neigh, lci_o) == 0)

> >  					kfree_skb(skb);

> >  			} else {

> > +				dev_put(dev);

> >  				kfree_skb(skb);

> >  			}

> >  		} else {

> 

> This is still not correct. With this code dev_put() could be called with

> NULL, which would cause a crash.

> 

> There is also a dev_put() missing if rose_rx_call_request() returns 0.

> 

> I think that this is the correct code:

> 

> diff --git a/net/rose/rose_loopback.c b/net/rose/rose_loopback.c

> index 7b094275ea8b..ff252ef73592 100644

> --- a/net/rose/rose_loopback.c

> +++ b/net/rose/rose_loopback.c

> @@ -96,11 +96,22 @@ static void rose_loopback_timer(struct timer_list *unused)

>  		}

>  

>  		if (frametype == ROSE_CALL_REQUEST) {

> -			if ((dev = rose_dev_get(dest)) != NULL) {

> -				if (rose_rx_call_request(skb, dev, rose_loopback_neigh, lci_o) == 0)

> -					kfree_skb(skb);

> -			} else {

> +			if (!rose_loopback_neigh->dev) {

>  				kfree_skb(skb);

> +				continue;

> +			}

> +

> +			dev = rose_dev_get(dest);

> +			if (!dev) {

> +				kfree_skb(skb);

> +				continue;

> +			}

> +

> +			if (rose_rx_call_request(skb, dev, rose_loopback_neigh,

> +						 lci_o) == 0) {

> +				dev_put(dev);

> +				kfree_skb(skb);

>  			}

>  		} else {

>  			kfree_skb(skb);

> 

> Please test this and resubmit it if it works.


Sure sir, I will test it and resend, if it works.


Thanks,
Anmol
Jakub Kicinski Nov. 20, 2020, 6:06 p.m. UTC | #5 
On Fri, 20 Nov 2020 00:40:43 +0530 Anmol Karn wrote:
> rose_send_frame() dereferences `neigh->dev` when called from

> rose_transmit_clear_request(), and the first occurrence of the

> `neigh` is in rose_loopback_timer() as `rose_loopback_neigh`,

> and it is initialized in rose_add_loopback_neigh() as NULL.

> i.e when `rose_loopback_neigh` used in rose_loopback_timer()

> its `->dev` was still NULL and rose_loopback_timer() was calling

> rose_rx_call_request() without checking for NULL.

> 

> - net/rose/rose_link.c

> This bug seems to get triggered in this line:

> 

> rose_call = (ax25_address *)neigh->dev->dev_addr;

> 

> Fix it by adding NULL checking for `rose_loopback_neigh->dev`

> in rose_loopback_timer().

> 

> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")

> Suggested-by: Jakub Kicinski <kuba@kernel.org>

> Reported-by: syzbot+a1c743815982d9496393@syzkaller.appspotmail.com

> Tested-by: syzbot+a1c743815982d9496393@syzkaller.appspotmail.com

> Link: https://syzkaller.appspot.com/bug?id=9d2a7ca8c7f2e4b682c97578dfa3f236258300b3

> Signed-off-by: Anmol Karn <anmol.karan123@gmail.com>


Applied to net, thanks!
diff mbox series

Patch

diff --git a/net/rose/rose_loopback.c b/net/rose/rose_loopback.c
index 7b094275ea8b..2c51756ed7bf 100644
--- a/net/rose/rose_loopback.c
+++ b/net/rose/rose_loopback.c
@@ -96,7 +96,8 @@  static void rose_loopback_timer(struct timer_list *unused)
 		}

 		if (frametype == ROSE_CALL_REQUEST) {
-			if ((dev = rose_dev_get(dest)) != NULL) {
+			dev = rose_dev_get(dest);
+			if (rose_loopback_neigh->dev && dev) {
 				if (rose_rx_call_request(skb, dev, rose_loopback_neigh, lci_o) == 0)
 					kfree_skb(skb);
 			} else {