[3.19,and,earlier] fib_rules: Fix dump_rules() not to exit early

From: Roland Dreier <roland@purestorage.com>

Backports of 41fc014332d9 ("fib_rules: fix fib rule dumps across
multiple skbs") introduced a regression in "ip rule show" - it ends up
dumping the first rule over and over and never exiting, because 3.19
and earlier are missing commit 053c095a82cf ("netlink: make
nlmsg_end() and genlmsg_end() void"), so fib_nl_fill_rule() ends up
returning skb->len (i.e. > 0) in the success case.

Fix this by checking the return code for < 0 instead of != 0.

Signed-off-by: Roland Dreier <roland@purestorage.com>
---
Hi, this is needed for all stable trees earlier than 4.0 that have
picked up 41fc014332d9; so far looks like at least 3.10.y and 3.14.y
have made such releases.

 net/core/fib_rules.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

On 10/05/2015, 07:29 PM, Roland Dreier wrote:
> From: Roland Dreier <roland@purestorage.com>
> 
> Backports of 41fc014332d9 ("fib_rules: fix fib rule dumps across
> multiple skbs") introduced a regression in "ip rule show" - it ends up
> dumping the first rule over and over and never exiting, because 3.19
> and earlier are missing commit 053c095a82cf ("netlink: make
> nlmsg_end() and genlmsg_end() void"), so fib_nl_fill_rule() ends up
> returning skb->len (i.e. > 0) in the success case.
> 
> Fix this by checking the return code for < 0 instead of != 0.
> 
> Signed-off-by: Roland Dreier <roland@purestorage.com>
> ---
> Hi, this is needed for all stable trees earlier than 4.0 that have
> picked up 41fc014332d9; so far looks like at least 3.10.y and 3.14.y
> have made such releases.
> 
>  net/core/fib_rules.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/core/fib_rules.c b/net/core/fib_rules.c
> index 627e517077e4..84340a2605ed 100644
> --- a/net/core/fib_rules.c
> +++ b/net/core/fib_rules.c
> @@ -606,7 +606,7 @@ static int dump_rules(struct sk_buff *skb, struct netlink_callback *cb,
>  		err = fib_nl_fill_rule(skb, rule, NETLINK_CB(cb->skb).portid,
>  				       cb->nlh->nlmsg_seq, RTM_NEWRULE,
>  				       NLM_F_MULTI, ops);
> -		if (err)
> +		if (err < 0)

I integrated the fix into the backport of 41fc014332d9 in 3.12 and made
a note in there. Thanks!

On Mon, 2015-10-05 at 10:29 -0700, Roland Dreier wrote:
> From: Roland Dreier <roland@purestorage.com>
> 
> Backports of 41fc014332d9 ("fib_rules: fix fib rule dumps across
> multiple skbs") introduced a regression in "ip rule show" - it ends up
> dumping the first rule over and over and never exiting, because 3.19
> and earlier are missing commit 053c095a82cf ("netlink: make
> nlmsg_end() and genlmsg_end() void"), so fib_nl_fill_rule() ends up
> returning skb->len (i.e. > 0) in the success case.
> 
> Fix this by checking the return code for < 0 instead of != 0.
> 
> Signed-off-by: Roland Dreier <roland@purestorage.com>
> ---
> Hi, this is needed for all stable trees earlier than 4.0 that have
> picked up 41fc014332d9; so far looks like at least 3.10.y and 3.14.y
> have made such releases.
[...]

Thanks, I'm folding this into the backported patch in 3.2.

Ben.

Hi Roland,

On Monday, 5. October 2015 10:29:28 Roland Dreier wrote:
> From: Roland Dreier <roland@purestorage.com>
> 
> Backports of 41fc014332d9 ("fib_rules: fix fib rule dumps across
> multiple skbs") introduced a regression in "ip rule show" - it ends up
> dumping the first rule over and over and never exiting, because 3.19
> and earlier are missing commit 053c095a82cf ("netlink: make
> nlmsg_end() and genlmsg_end() void"), so fib_nl_fill_rule() ends up
> returning skb->len (i.e. > 0) in the success case.
> 
> Fix this by checking the return code for < 0 instead of != 0.

thanks for this fix. You just saved me an afternoon of bisecting :)

I can confirm that this fixes the mentioned issue introduced in 3.14.54.
We have an automated ipsec VPN test that failed after the upgrade:
The "ip rule list" command was hanging forever.

Cheers,
Thomas

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On Mon, Oct 05, 2015 at 10:29:28AM -0700, Roland Dreier wrote:
> From: Roland Dreier <roland@purestorage.com>
> 
> Backports of 41fc014332d9 ("fib_rules: fix fib rule dumps across
> multiple skbs") introduced a regression in "ip rule show" - it ends up
> dumping the first rule over and over and never exiting, because 3.19
> and earlier are missing commit 053c095a82cf ("netlink: make
> nlmsg_end() and genlmsg_end() void"), so fib_nl_fill_rule() ends up
> returning skb->len (i.e. > 0) in the success case.
> 
> Fix this by checking the return code for < 0 instead of != 0.
> 
> Signed-off-by: Roland Dreier <roland@purestorage.com>
> ---
> Hi, this is needed for all stable trees earlier than 4.0 that have
> picked up 41fc014332d9; so far looks like at least 3.10.y and 3.14.y
> have made such releases.

Thanks for this, now applied to 3.10 and 3.14-stable trees.

greg k-h
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On Mon, Oct 05, 2015 at 10:29:28AM -0700, Roland Dreier wrote:
> From: Roland Dreier <roland@purestorage.com>
> 
> Backports of 41fc014332d9 ("fib_rules: fix fib rule dumps across
> multiple skbs") introduced a regression in "ip rule show" - it ends up
> dumping the first rule over and over and never exiting, because 3.19
> and earlier are missing commit 053c095a82cf ("netlink: make
> nlmsg_end() and genlmsg_end() void"), so fib_nl_fill_rule() ends up
> returning skb->len (i.e. > 0) in the success case.
> 
> Fix this by checking the return code for < 0 instead of != 0.
> 
> Signed-off-by: Roland Dreier <roland@purestorage.com>
> ---
> Hi, this is needed for all stable trees earlier than 4.0 that have
> picked up 41fc014332d9; so far looks like at least 3.10.y and 3.14.y
> have made such releases.
>

Thanks Roland, I'm queuing this fix for the 3.16 kernel as well.

Cheers,
--
Luís


>  net/core/fib_rules.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/core/fib_rules.c b/net/core/fib_rules.c
> index 627e517077e4..84340a2605ed 100644
> --- a/net/core/fib_rules.c
> +++ b/net/core/fib_rules.c
> @@ -606,7 +606,7 @@ static int dump_rules(struct sk_buff *skb, struct netlink_callback *cb,
>  		err = fib_nl_fill_rule(skb, rule, NETLINK_CB(cb->skb).portid,
>  				       cb->nlh->nlmsg_seq, RTM_NEWRULE,
>  				       NLM_F_MULTI, ops);
> -		if (err)
> +		if (err < 0)
>  			break;
>  skip:
>  		idx++;
> -- 
> 2.5.0
> 
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