* [PATCH] net/l2tp: Fix reference count leak in l2tp_udp_recv_core
@ 2021-09-09 4:32 Xiyu Yang
2021-09-09 9:01 ` Tom Parkin
2021-09-09 10:10 ` patchwork-bot+netdevbpf
0 siblings, 2 replies; 4+ messages in thread
From: Xiyu Yang @ 2021-09-09 4:32 UTC (permalink / raw)
To: David S. Miller, Jakub Kicinski, Cong Wang, Randy Dunlap,
Tom Parkin, Xin Xiong, Gong, Sishuai, Matthias Schiffer,
Xiyu Yang, Bhaskar Chowdhury, netdev, linux-kernel
Cc: yuanxzhang, Xin Tan
The reference count leak issue may take place in an error handling
path. If both conditions of tunnel->version == L2TP_HDR_VER_3 and the
return value of l2tp_v3_ensure_opt_in_linear is nonzero, the function
would directly jump to label invalid, without decrementing the reference
count of the l2tp_session object session increased earlier by
l2tp_tunnel_get_session(). This may result in refcount leaks.
Fix this issue by decrease the reference count before jumping to the
label invalid.
Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Signed-off-by: Xin Xiong <xiongx18@fudan.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
---
net/l2tp/l2tp_core.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index 53486b162f01..93271a2632b8 100644
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -869,8 +869,10 @@ static int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb)
}
if (tunnel->version == L2TP_HDR_VER_3 &&
- l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr))
+ l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr)) {
+ l2tp_session_dec_refcount(session);
goto invalid;
+ }
l2tp_recv_common(session, skb, ptr, optr, hdrflags, length);
l2tp_session_dec_refcount(session);
--
2.7.4
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH] net/l2tp: Fix reference count leak in l2tp_udp_recv_core
2021-09-09 4:32 [PATCH] net/l2tp: Fix reference count leak in l2tp_udp_recv_core Xiyu Yang
@ 2021-09-09 9:01 ` Tom Parkin
2021-09-09 9:10 ` Tom Parkin
2021-09-09 10:10 ` patchwork-bot+netdevbpf
1 sibling, 1 reply; 4+ messages in thread
From: Tom Parkin @ 2021-09-09 9:01 UTC (permalink / raw)
To: Xiyu Yang
Cc: David S. Miller, Jakub Kicinski, Cong Wang, Randy Dunlap,
Xin Xiong, Gong, Sishuai, Matthias Schiffer, Bhaskar Chowdhury,
netdev, linux-kernel, yuanxzhang, Xin Tan
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On Thu, Sep 09, 2021 at 12:32:00 +0800, Xiyu Yang wrote:
> The reference count leak issue may take place in an error handling
> path. If both conditions of tunnel->version == L2TP_HDR_VER_3 and the
> return value of l2tp_v3_ensure_opt_in_linear is nonzero, the function
> would directly jump to label invalid, without decrementing the reference
> count of the l2tp_session object session increased earlier by
> l2tp_tunnel_get_session(). This may result in refcount leaks.
I agree with your analysis. Thanks for catching this!
>
> Fix this issue by decrease the reference count before jumping to the
> label invalid.
>
> Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
> Signed-off-by: Xin Xiong <xiongx18@fudan.edu.cn>
> Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
> ---
> net/l2tp/l2tp_core.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
> index 53486b162f01..93271a2632b8 100644
> --- a/net/l2tp/l2tp_core.c
> +++ b/net/l2tp/l2tp_core.c
> @@ -869,8 +869,10 @@ static int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb)
> }
>
> if (tunnel->version == L2TP_HDR_VER_3 &&
> - l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr))
> + l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr)) {
> + l2tp_session_dec_refcount(session);
> goto invalid;
> + }
The error paths in l2tp_udp_recv_core are a bit convoluted because of
the check (!session || !session->recv_skb) which may or may not need
to drop a session reference if triggered.
I think it could be simplified since session->recv_skb is always set
for all the current session types in the tree, but doing that is probably
a little patch series on its own.
>
> l2tp_recv_common(session, skb, ptr, optr, hdrflags, length);
> l2tp_session_dec_refcount(session);
> --
> 2.7.4
>
--
Tom Parkin
Katalix Systems Ltd
https://katalix.com
Catalysts for your Embedded Linux software development
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^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] net/l2tp: Fix reference count leak in l2tp_udp_recv_core
2021-09-09 9:01 ` Tom Parkin
@ 2021-09-09 9:10 ` Tom Parkin
0 siblings, 0 replies; 4+ messages in thread
From: Tom Parkin @ 2021-09-09 9:10 UTC (permalink / raw)
To: Xiyu Yang
Cc: David S. Miller, Jakub Kicinski, Cong Wang, Randy Dunlap,
Xin Xiong, Gong, Sishuai, Matthias Schiffer, Bhaskar Chowdhury,
netdev, linux-kernel, yuanxzhang, Xin Tan
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On Thu, Sep 09, 2021 at 10:01:56 +0100, Tom Parkin wrote:
> On Thu, Sep 09, 2021 at 12:32:00 +0800, Xiyu Yang wrote:
> > The reference count leak issue may take place in an error handling
> > path. If both conditions of tunnel->version == L2TP_HDR_VER_3 and the
> > return value of l2tp_v3_ensure_opt_in_linear is nonzero, the function
> > would directly jump to label invalid, without decrementing the reference
> > count of the l2tp_session object session increased earlier by
> > l2tp_tunnel_get_session(). This may result in refcount leaks.
>
> I agree with your analysis. Thanks for catching this!
>
Also: I forgot to mention I think this fixes:
4522a70db7aa ("l2tp: fix reading optional fields of L2TPv3")
> >
> > Fix this issue by decrease the reference count before jumping to the
> > label invalid.
> >
> > Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
> > Signed-off-by: Xin Xiong <xiongx18@fudan.edu.cn>
> > Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
> > ---
> > net/l2tp/l2tp_core.c | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
> > index 53486b162f01..93271a2632b8 100644
> > --- a/net/l2tp/l2tp_core.c
> > +++ b/net/l2tp/l2tp_core.c
> > @@ -869,8 +869,10 @@ static int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb)
> > }
> >
> > if (tunnel->version == L2TP_HDR_VER_3 &&
> > - l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr))
> > + l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr)) {
> > + l2tp_session_dec_refcount(session);
> > goto invalid;
> > + }
>
> The error paths in l2tp_udp_recv_core are a bit convoluted because of
> the check (!session || !session->recv_skb) which may or may not need
> to drop a session reference if triggered.
>
> I think it could be simplified since session->recv_skb is always set
> for all the current session types in the tree, but doing that is probably
> a little patch series on its own.
>
> >
> > l2tp_recv_common(session, skb, ptr, optr, hdrflags, length);
> > l2tp_session_dec_refcount(session);
> > --
> > 2.7.4
> >
>
> --
> Tom Parkin
> Katalix Systems Ltd
> https://katalix.com
> Catalysts for your Embedded Linux software development
--
Tom Parkin
Katalix Systems Ltd
https://katalix.com
Catalysts for your Embedded Linux software development
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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] net/l2tp: Fix reference count leak in l2tp_udp_recv_core
2021-09-09 4:32 [PATCH] net/l2tp: Fix reference count leak in l2tp_udp_recv_core Xiyu Yang
2021-09-09 9:01 ` Tom Parkin
@ 2021-09-09 10:10 ` patchwork-bot+netdevbpf
1 sibling, 0 replies; 4+ messages in thread
From: patchwork-bot+netdevbpf @ 2021-09-09 10:10 UTC (permalink / raw)
To: Xiyu Yang
Cc: davem, kuba, cong.wang, rdunlap, tparkin, xiongx18, sishuai,
mschiffer, unixbhaskar, netdev, linux-kernel, yuanxzhang,
tanxin.ctf
Hello:
This patch was applied to netdev/net.git (refs/heads/master):
On Thu, 9 Sep 2021 12:32:00 +0800 you wrote:
> The reference count leak issue may take place in an error handling
> path. If both conditions of tunnel->version == L2TP_HDR_VER_3 and the
> return value of l2tp_v3_ensure_opt_in_linear is nonzero, the function
> would directly jump to label invalid, without decrementing the reference
> count of the l2tp_session object session increased earlier by
> l2tp_tunnel_get_session(). This may result in refcount leaks.
>
> [...]
Here is the summary with links:
- net/l2tp: Fix reference count leak in l2tp_udp_recv_core
https://git.kernel.org/netdev/net/c/9b6ff7eb6664
You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
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^ permalink raw reply [flat|nested] 4+ messages in thread
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2021-09-09 4:32 [PATCH] net/l2tp: Fix reference count leak in l2tp_udp_recv_core Xiyu Yang
2021-09-09 9:01 ` Tom Parkin
2021-09-09 9:10 ` Tom Parkin
2021-09-09 10:10 ` patchwork-bot+netdevbpf
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