Re: [PATCH] netfilter: nf_conntrack_sctp: fix build warning

Re: [PATCH] netfilter: nf_conntrack_sctp: fix build warning

[Patrick McHardy]

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Wu Fengguang wrote:
>> print some debug info would be better?
> 
> Like this one?
> +		pr_debug("Empty sctp packet\n");
> 
> Fengguang
> ---
> netfilter: nf_conntrack_sctp: fix build warning
> 
> net/netfilter/nf_conntrack_proto_sctp.c: In function ‘sctp_packet’:
> net/netfilter/nf_conntrack_proto_sctp.c:376: warning: array subscript is above array bounds

The warning is bogus, so we don't need a pr_debug() there.
I've applied your first patch with an unlikely() added and
a comment stating that the warning is bogus.


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commit a3e2913ffd3dec7f6975f680035670261ad5f56e
Author: Wu Fengguang <wfg@linux.intel.com>
Date:   Mon Nov 24 13:18:00 2008 +0100

    netfilter: nf_conntrack_sctp: fix build warning
    
    net/netfilter/nf_conntrack_proto_sctp.c: In function 'sctp_packet':
    net/netfilter/nf_conntrack_proto_sctp.c:376: warning: array subscript is above array bounds
    
    [Patrick; add unlikely and comment stating that the warning is bogus]
    
    Signed-off-by: Wu Fengguang <wfg@linux.intel.com>
    Signed-off-by: Patrick McHardy <kaber@trash.net>

diff --git a/net/netfilter/nf_conntrack_proto_sctp.c b/net/netfilter/nf_conntrack_proto_sctp.c
index c2bd457..1259ec6 100644
--- a/net/netfilter/nf_conntrack_proto_sctp.c
+++ b/net/netfilter/nf_conntrack_proto_sctp.c
@@ -373,6 +373,12 @@ static int sctp_packet(struct nf_conn *ct,
 	}
 	write_unlock_bh(&sctp_lock);
 
+	/* Avoid bogus warning, gcc doesn't realize do_basic_checks()
+	 * guarantees that there is at least one SCTP chunk.
+	 */
+	if (unlikely(new_state == SCTP_CONNTRACK_MAX))
+		goto out;
+
 	nf_ct_refresh_acct(ct, ctinfo, skb, sctp_timeouts[new_state]);
 
 	if (old_state == SCTP_CONNTRACK_COOKIE_ECHOED &&

Re: [PATCH] netfilter: nf_conntrack_sctp: fix build warning

[Wu Fengguang]

On Mon, Nov 24, 2008 at 02:23:16PM +0200, Patrick McHardy wrote:
> Wu Fengguang wrote:
> >> print some debug info would be better?
> > 
> > Like this one?
> > +		pr_debug("Empty sctp packet\n");
> > 
> > Fengguang
> > ---
> > netfilter: nf_conntrack_sctp: fix build warning
> > 
> > net/netfilter/nf_conntrack_proto_sctp.c: In function ‘sctp_packet’:
> > net/netfilter/nf_conntrack_proto_sctp.c:376: warning: array subscript is above array bounds
> 
> The warning is bogus, so we don't need a pr_debug() there.
> I've applied your first patch with an unlikely() added and
> a comment stating that the warning is bogus.

Thank you! I was expecting some better solution (and learn a bit) ;-)

> commit a3e2913ffd3dec7f6975f680035670261ad5f56e
> Author: Wu Fengguang <wfg@linux.intel.com>
> Date:   Mon Nov 24 13:18:00 2008 +0100
> 
>     netfilter: nf_conntrack_sctp: fix build warning
>     
>     net/netfilter/nf_conntrack_proto_sctp.c: In function 'sctp_packet':
>     net/netfilter/nf_conntrack_proto_sctp.c:376: warning: array subscript is above array bounds
>     
>     [Patrick; add unlikely and comment stating that the warning is bogus]
>     
>     Signed-off-by: Wu Fengguang <wfg@linux.intel.com>
>     Signed-off-by: Patrick McHardy <kaber@trash.net>
> 
> diff --git a/net/netfilter/nf_conntrack_proto_sctp.c b/net/netfilter/nf_conntrack_proto_sctp.c
> index c2bd457..1259ec6 100644
> --- a/net/netfilter/nf_conntrack_proto_sctp.c
> +++ b/net/netfilter/nf_conntrack_proto_sctp.c
> @@ -373,6 +373,12 @@ static int sctp_packet(struct nf_conn *ct,
>  	}
>  	write_unlock_bh(&sctp_lock);
>  
> +	/* Avoid bogus warning, gcc doesn't realize do_basic_checks()
> +	 * guarantees that there is at least one SCTP chunk.
> +	 */
> +	if (unlikely(new_state == SCTP_CONNTRACK_MAX))
> +		goto out;
> +

If do_basic_checks() guarantees that, why not Initialize new_state to 0?

---
diff --git a/net/netfilter/nf_conntrack_proto_sctp.c b/net/netfilter/nf_conntrack_proto_sctp.c
index ae8c260..218137d 100644
--- a/net/netfilter/nf_conntrack_proto_sctp.c
+++ b/net/netfilter/nf_conntrack_proto_sctp.c
@@ -317,7 +317,11 @@ static int sctp_packet(struct nf_conn *ct,
 		goto out;
 	}
 
-	old_state = new_state = SCTP_CONNTRACK_MAX;
+	/* Avoid bogus warning, gcc doesn't realize do_basic_checks()
+	 * guarantees that there is at least one SCTP chunk.
+	 */
+	old_state = new_state = 0;
+
 	write_lock_bh(&sctp_lock);
 	for_each_sctp_chunk (skb, sch, _sch, offset, dataoff, count) {
 		/* Special cases of Verification tag check (Sec 8.5.1) */
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Re: [PATCH] netfilter: nf_conntrack_sctp: fix build warning

[Patrick McHardy]

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Wu Fengguang wrote:
> On Mon, Nov 24, 2008 at 02:23:16PM +0200, Patrick McHardy wrote:
>> +	/* Avoid bogus warning, gcc doesn't realize do_basic_checks()
>> +	 * guarantees that there is at least one SCTP chunk.
>> +	 */
>> +	if (unlikely(new_state == SCTP_CONNTRACK_MAX))
>> +		goto out;
>> +
> 
> If do_basic_checks() guarantees that, why not Initialize new_state to 0?

Good point. I've replaced the patch by this one:


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commit 328bd8997dbb7184d5389e45c642af44ae6e9043
Author: Patrick McHardy <kaber@trash.net>
Date:   Mon Nov 24 13:44:55 2008 +0100

    netfilter: nf_conntrack_proto_sctp: avoid bogus warning
    
    net/netfilter/nf_conntrack_proto_sctp.c: In function 'sctp_packet':
    net/netfilter/nf_conntrack_proto_sctp.c:376: warning: array subscript is above array bounds
    
    gcc doesn't realize that do_basic_checks() guarantees that there is
    at least one valid chunk and thus new_state is never SCTP_CONNTRACK_MAX
    after the loop. Initialize to SCTP_CONNTRACK_NONE to avoid the warning.
    
    Based on patch by Wu Fengguang <wfg@linux.intel.com>
    
    Signed-off-by: Patrick McHardy <kaber@trash.net>

diff --git a/net/netfilter/nf_conntrack_proto_sctp.c b/net/netfilter/nf_conntrack_proto_sctp.c
index c2bd457..74e0379 100644
--- a/net/netfilter/nf_conntrack_proto_sctp.c
+++ b/net/netfilter/nf_conntrack_proto_sctp.c
@@ -317,7 +317,7 @@ static int sctp_packet(struct nf_conn *ct,
 		goto out;
 	}
 
-	old_state = new_state = SCTP_CONNTRACK_MAX;
+	old_state = new_state = SCTP_CONNTRACK_NONE;
 	write_lock_bh(&sctp_lock);
 	for_each_sctp_chunk (skb, sch, _sch, offset, dataoff, count) {
 		/* Special cases of Verification tag check (Sec 8.5.1) */

Re: [PATCH] netfilter: nf_conntrack_sctp: fix build warning

[Wu Fengguang]

On Mon, Nov 24, 2008 at 02:48:07PM +0200, Patrick McHardy wrote:
> Wu Fengguang wrote:
> > On Mon, Nov 24, 2008 at 02:23:16PM +0200, Patrick McHardy wrote:
> >> +	/* Avoid bogus warning, gcc doesn't realize do_basic_checks()
> >> +	 * guarantees that there is at least one SCTP chunk.
> >> +	 */
> >> +	if (unlikely(new_state == SCTP_CONNTRACK_MAX))
> >> +		goto out;
> >> +
> > 
> > If do_basic_checks() guarantees that, why not Initialize new_state to 0?
> 
> Good point. I've replaced the patch by this one:

Thanks!

Fengguang

Content-Description: x
> commit 328bd8997dbb7184d5389e45c642af44ae6e9043
> Author: Patrick McHardy <kaber@trash.net>
> Date:   Mon Nov 24 13:44:55 2008 +0100
> 
>     netfilter: nf_conntrack_proto_sctp: avoid bogus warning
>     
>     net/netfilter/nf_conntrack_proto_sctp.c: In function 'sctp_packet':
>     net/netfilter/nf_conntrack_proto_sctp.c:376: warning: array subscript is above array bounds
>     
>     gcc doesn't realize that do_basic_checks() guarantees that there is
>     at least one valid chunk and thus new_state is never SCTP_CONNTRACK_MAX
>     after the loop. Initialize to SCTP_CONNTRACK_NONE to avoid the warning.
>     
>     Based on patch by Wu Fengguang <wfg@linux.intel.com>
>     
>     Signed-off-by: Patrick McHardy <kaber@trash.net>
> 
> diff --git a/net/netfilter/nf_conntrack_proto_sctp.c b/net/netfilter/nf_conntrack_proto_sctp.c
> index c2bd457..74e0379 100644
> --- a/net/netfilter/nf_conntrack_proto_sctp.c
> +++ b/net/netfilter/nf_conntrack_proto_sctp.c
> @@ -317,7 +317,7 @@ static int sctp_packet(struct nf_conn *ct,
>  		goto out;
>  	}
>  
> -	old_state = new_state = SCTP_CONNTRACK_MAX;
> +	old_state = new_state = SCTP_CONNTRACK_NONE;
>  	write_lock_bh(&sctp_lock);
>  	for_each_sctp_chunk (skb, sch, _sch, offset, dataoff, count) {
>  		/* Special cases of Verification tag check (Sec 8.5.1) */