2021-03-12 20:12:58

by Alexander Lobakin

Subject: [PATCH net] flow_dissector: fix byteorder of dissected ICMP ID

flow_dissector_key_icmp::id is of type u16 (CPU byteorder),
ICMP header has its ID field in network byteorder obviously.
Sparse says:

net/core/flow_dissector.c:178:43: warning: restricted __be16 degrades to integer

Convert ID value to CPU byteorder when storing it into
flow_dissector_key_icmp.

Fixes: 5dec597e5cd0 ("flow_dissector: extract more ICMP information")
Signed-off-by: Alexander Lobakin <[email protected]>
---
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 2ef2224b3bff..a96a4f5de0ce 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -176,7 +176,7 @@ void skb_flow_get_icmp_tci(const struct sk_buff *skb,
* avoid confusion with packets without such field
*/
if (icmp_has_id(ih->type))
- key_icmp->id = ih->un.echo.id ? : 1;
+ key_icmp->id = ih->un.echo.id ? ntohs(ih->un.echo.id) : 1;
else
key_icmp->id = 0;
}
--
2.30.2

2021-03-14 20:42:14

by Jakub Sitnicki

Subject: Re: [PATCH net] flow_dissector: fix byteorder of dissected ICMP ID

On Fri, Mar 12, 2021 at 09:08 PM CET, Alexander Lobakin wrote:
> flow_dissector_key_icmp::id is of type u16 (CPU byteorder),
> ICMP header has its ID field in network byteorder obviously.
> Sparse says:
>
> net/core/flow_dissector.c:178:43: warning: restricted __be16 degrades to integer
>
> Convert ID value to CPU byteorder when storing it into
> flow_dissector_key_icmp.
>
> Fixes: 5dec597e5cd0 ("flow_dissector: extract more ICMP information")
> Signed-off-by: Alexander Lobakin <[email protected]>
> ---
> 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 2ef2224b3bff..a96a4f5de0ce 100644
> --- a/net/core/flow_dissector.c
> +++ b/net/core/flow_dissector.c
> @@ -176,7 +176,7 @@ void skb_flow_get_icmp_tci(const struct sk_buff *skb,
> * avoid confusion with packets without such field
> */
> if (icmp_has_id(ih->type))
> - key_icmp->id = ih->un.echo.id ? : 1;
> + key_icmp->id = ih->un.echo.id ? ntohs(ih->un.echo.id) : 1;
> else
> key_icmp->id = 0;
> }

Smells like a breaking change for existing consumers of this value.

How about we change the type of flow_dissector_key_icmp{}.id to __be16
instead to make sparse happy?

2021-03-14 20:47:37

by Vladimir Oltean

Subject: Re: [PATCH net] flow_dissector: fix byteorder of dissected ICMP ID

On Sun, Mar 14, 2021 at 09:21:40PM +0100, Jakub Sitnicki wrote:
> On Fri, Mar 12, 2021 at 09:08 PM CET, Alexander Lobakin wrote:
> > flow_dissector_key_icmp::id is of type u16 (CPU byteorder),
> > ICMP header has its ID field in network byteorder obviously.
> > Sparse says:
> >
> > net/core/flow_dissector.c:178:43: warning: restricted __be16 degrades to integer
> >
> > Convert ID value to CPU byteorder when storing it into
> > flow_dissector_key_icmp.
> >
> > Fixes: 5dec597e5cd0 ("flow_dissector: extract more ICMP information")
> > Signed-off-by: Alexander Lobakin <[email protected]>
> > ---
> > 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 2ef2224b3bff..a96a4f5de0ce 100644
> > --- a/net/core/flow_dissector.c
> > +++ b/net/core/flow_dissector.c
> > @@ -176,7 +176,7 @@ void skb_flow_get_icmp_tci(const struct sk_buff *skb,
> > * avoid confusion with packets without such field
> > */
> > if (icmp_has_id(ih->type))
> > - key_icmp->id = ih->un.echo.id ? : 1;
> > + key_icmp->id = ih->un.echo.id ? ntohs(ih->un.echo.id) : 1;
> > else
> > key_icmp->id = 0;
> > }
>
> Smells like a breaking change for existing consumers of this value.
>
> How about we change the type of flow_dissector_key_icmp{}.id to __be16
> instead to make sparse happy?

The struct flow_dissector_key_icmp::id only appears to be used in
bond_xmit_hash, and there, the exact value doesn't seem to matter.

This appears to be a real bug and not just to appease sparse:
ih->un.echo.id has one endianness and "1" has another. Both cannot
be correct.

2021-03-14 21:40:48

by David Miller

Subject: Re: [PATCH net] flow_dissector: fix byteorder of dissected ICMP ID

From: Vladimir Oltean <[email protected]>
Date: Sun, 14 Mar 2021 20:44:49 +0000

> On Sun, Mar 14, 2021 at 09:21:40PM +0100, Jakub Sitnicki wrote:
>> On Fri, Mar 12, 2021 at 09:08 PM CET, Alexander Lobakin wrote:
>>
>> Smells like a breaking change for existing consumers of this value.
>>
>> How about we change the type of flow_dissector_key_icmp{}.id to __be16
>> instead to make sparse happy?
>
> The struct flow_dissector_key_icmp::id only appears to be used in
> bond_xmit_hash, and there, the exact value doesn't seem to matter.
>
> This appears to be a real bug and not just to appease sparse:
> ih->un.echo.id has one endianness and "1" has another. Both cannot
> be correct.

Agreed, so I will apply this, thanks.

2021-03-14 22:41:54

by patchwork-bot+netdevbpf

Subject: Re: [PATCH net] flow_dissector: fix byteorder of dissected ICMP ID

Hello:

This patch was applied to netdev/net.git (refs/heads/master):

On Fri, 12 Mar 2021 20:08:57 +0000 you wrote:
> flow_dissector_key_icmp::id is of type u16 (CPU byteorder),
> ICMP header has its ID field in network byteorder obviously.
> Sparse says:
>
> net/core/flow_dissector.c:178:43: warning: restricted __be16 degrades to integer
>
> Convert ID value to CPU byteorder when storing it into
> flow_dissector_key_icmp.
>
> [...]

Here is the summary with links:
- [net] flow_dissector: fix byteorder of dissected ICMP ID
https://git.kernel.org/netdev/net/c/a25f82228542

You are awesome, thank you!
--
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