[PATCH] flow_dissector: Pre-initialize ip_proto in __skb_flow_dissect()

[PATCH] flow_dissector: Pre-initialize ip_proto in __skb_flow_dissect()

[Geert Uytterhoeven]

net/core/flow_dissector.c: In function ‘__skb_flow_dissect’:
net/core/flow_dissector.c:132: warning: ‘ip_proto’ may be used uninitialized in this function

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
---
This may be a false positive, but the state machine in
__skb_flow_dissect() is a bit hard to follow.
As I believe it is controlled by a packet received from the network, the
only safe thing to do is to pre-initialize ip_proto.
---
 net/core/flow_dissector.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index 476e5dda59e19822..2a834c6179b9973e 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -129,7 +129,7 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
 	struct flow_dissector_key_ports *key_ports;
 	struct flow_dissector_key_tags *key_tags;
 	struct flow_dissector_key_keyid *key_keyid;
-	u8 ip_proto;
+	u8 ip_proto = 0;
 
 	if (!data) {
 		data = skb->data;
-- 
1.9.1

Re: [PATCH] flow_dissector: Pre-initialize ip_proto in __skb_flow_dissect()

[David Miller]

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From: Geert Uytterhoeven <geert@linux-m68k.org>
Date: Thu, 25 Jun 2015 15:10:32 +0200

> net/core/flow_dissector.c: In function ¡__skb_flow_dissect¢:
> net/core/flow_dissector.c:132: warning: ¡ip_proto¢ may be used uninitialized in this function
> 
> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
> ---
> This may be a false positive, but the state machine in
> __skb_flow_dissect() is a bit hard to follow.
> As I believe it is controlled by a packet received from the network, the
> only safe thing to do is to pre-initialize ip_proto.

Actually I think this is a real bug, because for the ETH_P_MPLS_* cases I cannot
see what will always set ip_proto before it gets used as an input.
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Re: [PATCH] flow_dissector: Pre-initialize ip_proto in __skb_flow_dissect()

[Jiri Pirko]

Thu, Jun 25, 2015 at 03:33:31PM CEST, davem@davemloft.net wrote:
>From: Geert Uytterhoeven <geert@linux-m68k.org>
>Date: Thu, 25 Jun 2015 15:10:32 +0200
>
>> net/core/flow_dissector.c: In function ‘__skb_flow_dissect’:
>> net/core/flow_dissector.c:132: warning: ‘ip_proto’ may be used uninitialized in this function
>> 
>> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
>> ---
>> This may be a false positive, but the state machine in
>> __skb_flow_dissect() is a bit hard to follow.
>> As I believe it is controlled by a packet received from the network, the
>> only safe thing to do is to pre-initialize ip_proto.
>
>Actually I think this is a real bug, because for the ETH_P_MPLS_* cases I cannot
>see what will always set ip_proto before it gets used as an input.

I think that MPLS cases are ok. In this case, return is always hit.
I believe this is false positive.

Re: [PATCH] flow_dissector: Pre-initialize ip_proto in __skb_flow_dissect()

[Tom Herbert]

On Thu, Jun 25, 2015 at 6:10 AM, Geert Uytterhoeven
<geert@linux-m68k.org> wrote:
> net/core/flow_dissector.c: In function ‘__skb_flow_dissect’:
> net/core/flow_dissector.c:132: warning: ‘ip_proto’ may be used uninitialized in this function
>
> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
> ---
> This may be a false positive, but the state machine in
> __skb_flow_dissect() is a bit hard to follow.
> As I believe it is controlled by a packet received from the network, the
> only safe thing to do is to pre-initialize ip_proto.
> ---
>  net/core/flow_dissector.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
> index 476e5dda59e19822..2a834c6179b9973e 100644
> --- a/net/core/flow_dissector.c
> +++ b/net/core/flow_dissector.c
> @@ -129,7 +129,7 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
>         struct flow_dissector_key_ports *key_ports;
>         struct flow_dissector_key_tags *key_tags;
>         struct flow_dissector_key_keyid *key_keyid;
> -       u8 ip_proto;
> +       u8 ip_proto = 0;
>
>         if (!data) {
>                 data = skb->data;
> --
> 1.9.1
>

Acked-by: Tom Herbert <tom@herbertland.com>

Re: [PATCH] flow_dissector: Pre-initialize ip_proto in __skb_flow_dissect()

[David Miller]

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From: Geert Uytterhoeven <geert@linux-m68k.org>
Date: Thu, 25 Jun 2015 15:10:32 +0200

> net/core/flow_dissector.c: In function ¡__skb_flow_dissect¢:
> net/core/flow_dissector.c:132: warning: ¡ip_proto¢ may be used uninitialized in this function
> 
> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

Applied, thanks.
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