Subject: Re: [PATCH iwl-net v3] ice: Add netif_device_attach/detach into PF reset flow

From: Przemek Kitszel <[email-masked]>
Date: Mon, 19 Aug 2024 10:47:19 +0200

On 8/19/24 10:21, Dawid Osuchowski wrote:
> Ethtool callbacks can be executed while reset is in progress and try to
> access deleted resources, e.g. getting coalesce settings can result in a
> NULL pointer dereference seen below.
> 
> Reproduction steps:
> Once the driver is fully initialized, trigger reset:
> 	# echo 1 > /sys/class/net/<interface>/device/reset
> when reset is in progress try to get coalesce settings using ethtool:
> 	# ethtool -c <interface>
> 
> BUG: kernel NULL pointer dereference, address: 0000000000000020
> PGD 0 P4D 0
> Oops: Oops: 0000 [#1] PREEMPT SMP PTI
> CPU: 11 PID: 19713 Comm: ethtool Tainted: G S                 6.10.0-rc7+ #7
> RIP: 0010:ice_get_q_coalesce+0x2e/0xa0 [ice]
> RSP: 0018:ffffbab1e9bcf6a8 EFLAGS: 00010206
> RAX: 000000000000000c RBX: ffff94512305b028 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: ffff9451c3f2e588 RDI: ffff9451c3f2e588
> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
> R10: ffff9451c3f2e580 R11: 000000000000001f R12: ffff945121fa9000
> R13: ffffbab1e9bcf760 R14: 0000000000000013 R15: ffffffff9e65dd40
> FS:  00007faee5fbe740(0000) GS:ffff94546fd80000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000000000020 CR3: 0000000106c2e005 CR4: 00000000001706f0
> Call Trace:
> <TASK>
> ice_get_coalesce+0x17/0x30 [ice]
> coalesce_prepare_data+0x61/0x80
> ethnl_default_doit+0xde/0x340
> genl_family_rcv_msg_doit+0xf2/0x150
> genl_rcv_msg+0x1b3/0x2c0
> netlink_rcv_skb+0x5b/0x110
> genl_rcv+0x28/0x40
> netlink_unicast+0x19c/0x290
> netlink_sendmsg+0x222/0x490
> __sys_sendto+0x1df/0x1f0
> __x64_sys_sendto+0x24/0x30
> do_syscall_64+0x82/0x160
> entry_SYSCALL_64_after_hwframe+0x76/0x7e
> RIP: 0033:0x7faee60d8e27
> 
> Calling netif_device_detach() before reset makes the net core not call
> the driver when ethtool command is issued, the attempt to execute an
> ethtool command during reset will result in the following message:
> 
>      netlink error: No such device
> 
> instead of NULL pointer dereference. Once reset is done and
> ice_rebuild() is executing, the netif_device_attach() is called to allow
> for ethtool operations to occur again in a safe manner.
> 
> Fixes: fcea6f3da546 ("ice: Add stats and ethtool support")
> Suggested-by: Jakub Kicinski <[email-masked]>
> Reviewed-by: Igor Bagnucki <[email-masked]>
> Signed-off-by: Dawid Osuchowski <[email-masked]>
> ---
> Changes since v1:
> * Changed Fixes tag to point to another commit
> * Minified the stacktrace
> 
> Changes since v2:
> * Moved netif_device_attach() directly into ice_rebuild() and perform it
>    only on main vsi
> 
> Suggestion from Kuba: https://lore.kernel.org/netdev/[email-masked]/
> Previous attempt (dropped because it introduced regression with link up): https://lore.kernel.org/netdev/[email-masked]/
> ---
>   drivers/net/ethernet/intel/ice/ice_main.c | 6 ++++++
>   1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/net/ethernet/intel/ice/ice_main.c b/drivers/net/ethernet/intel/ice/ice_main.c
> index eaa73cc200f4..27ec5d8d5810 100644
> --- a/drivers/net/ethernet/intel/ice/ice_main.c
> +++ b/drivers/net/ethernet/intel/ice/ice_main.c
> @@ -608,6 +608,8 @@ ice_prepare_for_reset(struct ice_pf *pf, enum ice_reset_req reset_type)
>   			memset(&vsi->mqprio_qopt, 0, sizeof(vsi->mqprio_qopt));
>   		}
>   	}
> +	if (vsi->netdev)
> +		netif_device_detach(vsi->netdev);
>   skip:
>   
>   	/* clear SW filtering DB */
> @@ -7731,6 +7733,10 @@ static void ice_rebuild(struct ice_pf *pf, enum ice_reset_req reset_type)
>   		ice_rebuild_arfs(pf);
>   	}
>   
> +	struct ice_vsi *vsi = ice_get_main_vsi(pf);

you should separate declaration statements from expressions by one blank
line; we also put declarations at the very front of the scope

> +	if (vsi && vsi->netdev)
> +		netif_device_attach(vsi->netdev);
> +
>   	ice_update_pf_netdev_link(pf);
>   
>   	/* tell the firmware we are up */