[PATCH 4.19 10/61] sctp: Free cookie before we memdup a new one

[PATCH 4.19 10/61] sctp: Free cookie before we memdup a new one

[Greg Kroah-Hartman]

From: Neil Horman <nhorman@tuxdriver.com>

[ Upstream commit ce950f1050cece5e406a5cde723c69bba60e1b26 ]

Based on comments from Xin, even after fixes for our recent syzbot
report of cookie memory leaks, its possible to get a resend of an INIT
chunk which would lead to us leaking cookie memory.

To ensure that we don't leak cookie memory, free any previously
allocated cookie first.

Change notes
v1->v2
update subsystem tag in subject (davem)
repeat kfree check for peer_random and peer_hmacs (xin)

v2->v3
net->sctp
also free peer_chunks

v3->v4
fix subject tags

v4->v5
remove cut line

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Reported-by: syzbot+f7e9153b037eac9b1df8@syzkaller.appspotmail.com
CC: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
CC: Xin Long <lucien.xin@gmail.com>
CC: "David S. Miller" <davem@davemloft.net>
CC: netdev@vger.kernel.org
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/sctp/sm_make_chunk.c |    8 ++++++++
 1 file changed, 8 insertions(+)

--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c
@@ -2600,6 +2600,8 @@ do_addr_param:
 	case SCTP_PARAM_STATE_COOKIE:
 		asoc->peer.cookie_len =
 			ntohs(param.p->length) - sizeof(struct sctp_paramhdr);
+		if (asoc->peer.cookie)
+			kfree(asoc->peer.cookie);
 		asoc->peer.cookie = kmemdup(param.cookie->body, asoc->peer.cookie_len, gfp);
 		if (!asoc->peer.cookie)
 			retval = 0;
@@ -2664,6 +2666,8 @@ do_addr_param:
 			goto fall_through;
 
 		/* Save peer's random parameter */
+		if (asoc->peer.peer_random)
+			kfree(asoc->peer.peer_random);
 		asoc->peer.peer_random = kmemdup(param.p,
 					    ntohs(param.p->length), gfp);
 		if (!asoc->peer.peer_random) {
@@ -2677,6 +2681,8 @@ do_addr_param:
 			goto fall_through;
 
 		/* Save peer's HMAC list */
+		if (asoc->peer.peer_hmacs)
+			kfree(asoc->peer.peer_hmacs);
 		asoc->peer.peer_hmacs = kmemdup(param.p,
 					    ntohs(param.p->length), gfp);
 		if (!asoc->peer.peer_hmacs) {
@@ -2692,6 +2698,8 @@ do_addr_param:
 		if (!ep->auth_enable)
 			goto fall_through;
 
+		if (asoc->peer.peer_chunks)
+			kfree(asoc->peer.peer_chunks);
 		asoc->peer.peer_chunks = kmemdup(param.p,
 					    ntohs(param.p->length), gfp);
 		if (!asoc->peer.peer_chunks)

Re: [PATCH 4.19 10/61] sctp: Free cookie before we memdup a new one

[Pavel Machek]

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Hi!

On Thu 2019-06-20 19:57:05, Greg Kroah-Hartman wrote:
> From: Neil Horman <nhorman@tuxdriver.com>
> 
> [ Upstream commit ce950f1050cece5e406a5cde723c69bba60e1b26 ]
> 
> Based on comments from Xin, even after fixes for our recent syzbot
> report of cookie memory leaks, its possible to get a resend of an INIT
> chunk which would lead to us leaking cookie memory.
> 

> --- a/net/sctp/sm_make_chunk.c
> +++ b/net/sctp/sm_make_chunk.c
> @@ -2600,6 +2600,8 @@ do_addr_param:
>  	case SCTP_PARAM_STATE_COOKIE:
>  		asoc->peer.cookie_len =
>  			ntohs(param.p->length) - sizeof(struct sctp_paramhdr);
> +		if (asoc->peer.cookie)
> +			kfree(asoc->peer.cookie);
>  		asoc->peer.cookie = kmemdup(param.cookie->body, asoc->peer.cookie_len, gfp);
>  		if (!asoc->peer.cookie)
>  			retval = 0;

kfree() handles NULL just fine. Can we simply work without the tests
and save a bit of code?

										Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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