[PATCH net v3] bonding: Fix unnecessary warnings and logs from bond_xdp_get_xmit_slave()

[PATCH net v3] bonding: Fix unnecessary warnings and logs from bond_xdp_get_xmit_slave()

[Jiwon Kim]

syzbot reported a WARNING in bond_xdp_get_xmit_slave. To reproduce
this[1], one bond device (bond1) has xdpdrv, which increases
bpf_master_redirect_enabled_key. Another bond device (bond0) which is
unsupported by XDP but its slave (veth3) has xdpgeneric that returns
XDP_TX. This triggers WARN_ON_ONCE() from the xdp_master_redirect().
To reduce unnecessary warnings and improve log management, we need to
delete the WARN_ON_ONCE() and add ratelimit to the netdev_err().

[1] Steps to reproduce:
    # Needs tx_xdp with return XDP_TX;
    ip l add veth0 type veth peer veth1
    ip l add veth3 type veth peer veth4
    ip l add bond0 type bond mode 6 # BOND_MODE_ALB, unsupported by XDP
    ip l add bond1 type bond # BOND_MODE_ROUNDROBIN by default
    ip l set veth0 master bond1
    ip l set bond1 up
    # Increases bpf_master_redirect_enabled_key
    ip l set dev bond1 xdpdrv object tx_xdp.o section xdp_tx
    ip l set veth3 master bond0
    ip l set bond0 up
    ip l set veth4 up
    # Triggers WARN_ON_ONCE() from the xdp_master_redirect()
    ip l set veth3 xdpgeneric object tx_xdp.o section xdp_tx

Reported-by: syzbot+c187823a52ed505b2257@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=c187823a52ed505b2257
Fixes: 9e2ee5c7e7c3 ("net, bonding: Add XDP support to the bonding driver")
Signed-off-by: Jiwon Kim <jiwonaid0@gmail.com>
---
v3: Fix subject and description
v2: Change the patch to fix bond_xdp_get_xmit_slave
---
 drivers/net/bonding/bond_main.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index b560644ee1b1..b1bffd8e9a95 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -5610,9 +5610,9 @@ bond_xdp_get_xmit_slave(struct net_device *bond_dev, struct xdp_buff *xdp)
 		break;
 
 	default:
-		/* Should never happen. Mode guarded by bond_xdp_check() */
-		netdev_err(bond_dev, "Unknown bonding mode %d for xdp xmit\n", BOND_MODE(bond));
-		WARN_ON_ONCE(1);
+		if (net_ratelimit())
+			netdev_err(bond_dev, "Unknown bonding mode %d for xdp xmit\n",
+				   BOND_MODE(bond));
 		return NULL;
 	}
 
-- 
2.43.0

Re: [PATCH net v3] bonding: Fix unnecessary warnings and logs from bond_xdp_get_xmit_slave()

[Nikolay Aleksandrov]

On 18/09/2024 17:06, Jiwon Kim wrote:
> syzbot reported a WARNING in bond_xdp_get_xmit_slave. To reproduce
> this[1], one bond device (bond1) has xdpdrv, which increases
> bpf_master_redirect_enabled_key. Another bond device (bond0) which is
> unsupported by XDP but its slave (veth3) has xdpgeneric that returns
> XDP_TX. This triggers WARN_ON_ONCE() from the xdp_master_redirect().
> To reduce unnecessary warnings and improve log management, we need to
> delete the WARN_ON_ONCE() and add ratelimit to the netdev_err().
> 
> [1] Steps to reproduce:
>     # Needs tx_xdp with return XDP_TX;
>     ip l add veth0 type veth peer veth1
>     ip l add veth3 type veth peer veth4
>     ip l add bond0 type bond mode 6 # BOND_MODE_ALB, unsupported by XDP
>     ip l add bond1 type bond # BOND_MODE_ROUNDROBIN by default
>     ip l set veth0 master bond1
>     ip l set bond1 up
>     # Increases bpf_master_redirect_enabled_key
>     ip l set dev bond1 xdpdrv object tx_xdp.o section xdp_tx
>     ip l set veth3 master bond0
>     ip l set bond0 up
>     ip l set veth4 up
>     # Triggers WARN_ON_ONCE() from the xdp_master_redirect()
>     ip l set veth3 xdpgeneric object tx_xdp.o section xdp_tx
> 
> Reported-by: syzbot+c187823a52ed505b2257@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=c187823a52ed505b2257
> Fixes: 9e2ee5c7e7c3 ("net, bonding: Add XDP support to the bonding driver")
> Signed-off-by: Jiwon Kim <jiwonaid0@gmail.com>
> ---
> v3: Fix subject and description
> v2: Change the patch to fix bond_xdp_get_xmit_slave
> ---
>  drivers/net/bonding/bond_main.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index b560644ee1b1..b1bffd8e9a95 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -5610,9 +5610,9 @@ bond_xdp_get_xmit_slave(struct net_device *bond_dev, struct xdp_buff *xdp)
>  		break;
>  
>  	default:
> -		/* Should never happen. Mode guarded by bond_xdp_check() */
> -		netdev_err(bond_dev, "Unknown bonding mode %d for xdp xmit\n", BOND_MODE(bond));
> -		WARN_ON_ONCE(1);
> +		if (net_ratelimit())
> +			netdev_err(bond_dev, "Unknown bonding mode %d for xdp xmit\n",
> +				   BOND_MODE(bond));
>  		return NULL;
>  	}
>  

Looks good to me, but next time wait 1 day before reposting another version.
Signed-off-by: Nikolay Aleksandrov <razor@blackwall.org>

Re: [PATCH net v3] bonding: Fix unnecessary warnings and logs from bond_xdp_get_xmit_slave()

[Paolo Abeni]

On 9/18/24 16:06, Jiwon Kim wrote:
> syzbot reported a WARNING in bond_xdp_get_xmit_slave. To reproduce
> this[1], one bond device (bond1) has xdpdrv, which increases
> bpf_master_redirect_enabled_key. Another bond device (bond0) which is
> unsupported by XDP but its slave (veth3) has xdpgeneric that returns
> XDP_TX. This triggers WARN_ON_ONCE() from the xdp_master_redirect().
> To reduce unnecessary warnings and improve log management, we need to
> delete the WARN_ON_ONCE() and add ratelimit to the netdev_err().
> 
> [1] Steps to reproduce:
>      # Needs tx_xdp with return XDP_TX;
>      ip l add veth0 type veth peer veth1
>      ip l add veth3 type veth peer veth4
>      ip l add bond0 type bond mode 6 # BOND_MODE_ALB, unsupported by XDP
>      ip l add bond1 type bond # BOND_MODE_ROUNDROBIN by default
>      ip l set veth0 master bond1
>      ip l set bond1 up
>      # Increases bpf_master_redirect_enabled_key
>      ip l set dev bond1 xdpdrv object tx_xdp.o section xdp_tx
>      ip l set veth3 master bond0
>      ip l set bond0 up
>      ip l set veth4 up
>      # Triggers WARN_ON_ONCE() from the xdp_master_redirect()
>      ip l set veth3 xdpgeneric object tx_xdp.o section xdp_tx
> 
> Reported-by: syzbot+c187823a52ed505b2257@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=c187823a52ed505b2257
> Fixes: 9e2ee5c7e7c3 ("net, bonding: Add XDP support to the bonding driver")
> Signed-off-by: Jiwon Kim <jiwonaid0@gmail.com>

Isn't the above issue completely addressed by explicitly checking for 
bond->prog in bond_xdp_get_xmit_slave()? Or would that broke some use-case?

Thanks,

Paolo

Re: [PATCH net v3] bonding: Fix unnecessary warnings and logs from bond_xdp_get_xmit_slave()

[Nikolay Aleksandrov]

On 9/24/24 13:20, Paolo Abeni wrote:
> On 9/18/24 16:06, Jiwon Kim wrote:
>> syzbot reported a WARNING in bond_xdp_get_xmit_slave. To reproduce
>> this[1], one bond device (bond1) has xdpdrv, which increases
>> bpf_master_redirect_enabled_key. Another bond device (bond0) which is
>> unsupported by XDP but its slave (veth3) has xdpgeneric that returns
>> XDP_TX. This triggers WARN_ON_ONCE() from the xdp_master_redirect().
>> To reduce unnecessary warnings and improve log management, we need to
>> delete the WARN_ON_ONCE() and add ratelimit to the netdev_err().
>>
>> [1] Steps to reproduce:
>>      # Needs tx_xdp with return XDP_TX;
>>      ip l add veth0 type veth peer veth1
>>      ip l add veth3 type veth peer veth4
>>      ip l add bond0 type bond mode 6 # BOND_MODE_ALB, unsupported by XDP
>>      ip l add bond1 type bond # BOND_MODE_ROUNDROBIN by default
>>      ip l set veth0 master bond1
>>      ip l set bond1 up
>>      # Increases bpf_master_redirect_enabled_key
>>      ip l set dev bond1 xdpdrv object tx_xdp.o section xdp_tx
>>      ip l set veth3 master bond0
>>      ip l set bond0 up
>>      ip l set veth4 up
>>      # Triggers WARN_ON_ONCE() from the xdp_master_redirect()
>>      ip l set veth3 xdpgeneric object tx_xdp.o section xdp_tx
>>
>> Reported-by: syzbot+c187823a52ed505b2257@syzkaller.appspotmail.com
>> Closes: https://syzkaller.appspot.com/bug?extid=c187823a52ed505b2257
>> Fixes: 9e2ee5c7e7c3 ("net, bonding: Add XDP support to the bonding driver")
>> Signed-off-by: Jiwon Kim <jiwonaid0@gmail.com>
> 
> Isn't the above issue completely addressed by explicitly checking for 
> bond->prog in bond_xdp_get_xmit_slave()? Or would that broke some use-case?
> 
> Thanks,
> 
> Paolo
> 

There isn't much difference with this patch, bond_xdp_get_xmit_slave()
always returns either a slave or NULL, either way you'd return NULL.

It does have a potential to break some weird setup, but I can't
currently come up with one where bond_xdp_get_xmit_slave is used and
xdp_prog is not set, so I don't have a preference about which way
to fix it. :)

Cheers,
 Nik

Re: [PATCH net v3] bonding: Fix unnecessary warnings and logs from bond_xdp_get_xmit_slave()

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Paolo Abeni <pabeni@redhat.com>:

On Wed, 18 Sep 2024 14:06:02 +0000 you wrote:
> syzbot reported a WARNING in bond_xdp_get_xmit_slave. To reproduce
> this[1], one bond device (bond1) has xdpdrv, which increases
> bpf_master_redirect_enabled_key. Another bond device (bond0) which is
> unsupported by XDP but its slave (veth3) has xdpgeneric that returns
> XDP_TX. This triggers WARN_ON_ONCE() from the xdp_master_redirect().
> To reduce unnecessary warnings and improve log management, we need to
> delete the WARN_ON_ONCE() and add ratelimit to the netdev_err().
> 
> [...]

Here is the summary with links:
  - [net,v3] bonding: Fix unnecessary warnings and logs from bond_xdp_get_xmit_slave()
    https://git.kernel.org/netdev/net/c/0cbfd45fbcf0

You are awesome, thank you!
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