RE: [Intel-wired-lan] [PATCH v3] igb: Add lock to avoid data race

[Jankowski, Konrad0]

> -----Original Message-----
> From: Intel-wired-lan <intel-wired-lan-bounces@xxxxxxxxxx> On Behalf Of
> Lin Ma
> Sent: Tuesday, August 9, 2022 9:36 AM
> To: Brandeburg, Jesse <jesse.brandeburg@xxxxxxxxx>; Nguyen, Anthony L
> <anthony.l.nguyen@xxxxxxxxx>; davem@xxxxxxxxxxxxx;
> edumazet@xxxxxxxxxx; kuba@xxxxxxxxxx; pabeni@xxxxxxxxxx;
> ast@xxxxxxxxxx; daniel@xxxxxxxxxxxxx; hawk@xxxxxxxxxx;
> john.fastabend@xxxxxxxxx; intel-wired-lan@xxxxxxxxxxxxxxxx;
> netdev@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> bpf@xxxxxxxxxxxxxxx
> Cc: Lin Ma <linma@xxxxxxxxxx>
> Subject: [Intel-wired-lan] [PATCH v3] igb: Add lock to avoid data race
> 
> The commit c23d92b80e0b ("igb: Teardown SR-IOV before
> unregister_netdev()") places the unregister_netdev() call after the
> igb_disable_sriov() call to avoid functionality issue.
> 
> However, it introduces several race conditions when detaching a device.
> For example, when .remove() is called, the below interleaving leads to use-
> after-free.
> 
>  (FREE from device detaching)      |   (USE from netdev core)
> igb_remove                         |  igb_ndo_get_vf_config
>  igb_disable_sriov                 |  vf >= adapter->vfs_allocated_count?
>   kfree(adapter->vf_data)          |
>   adapter->vfs_allocated_count = 0 |
>                                    |    memcpy(... adapter->vf_data[vf]
> 
> Moreover, the igb_disable_sriov() also suffers from data race with the
> requests from VF driver.
> 
>  (FREE from device detaching)      |   (USE from requests)
> igb_remove                         |  igb_msix_other
>  igb_disable_sriov                 |   igb_msg_task
>   kfree(adapter->vf_data)          |    vf < adapter->vfs_allocated_count
>   adapter->vfs_allocated_count = 0 |
> 
> To this end, this commit first eliminates the data races from netdev core by
> using rtnl_lock (similar to commit 719479230893 ("dpaa2-eth: add MAC/PHY
> support through phylink")). And then adds a spinlock to eliminate races from
> driver requests. (similar to commit 1e53834ce541
> ("ixgbe: Add locking to prevent panic when setting sriov_numvfs to zero")
> 
> 
> Fixes: c23d92b80e0b ("igb: Teardown SR-IOV before unregister_netdev()")
> Signed-off-by: Lin Ma <linma@xxxxxxxxxx>
> ---
> V2 -> V3:  make the commit message much clear
> V1 -> V2:  fix typo in title idb -> igb
> V0 -> V1:  change title from "Add rtnl_lock" to "Add lock"
>            add additional spinlock as suggested by Jakub, according to
>            1e53834ce541 ("ixgbe: Add locking to prevent panic when setting
>            sriov_numvfs to zero")
> 
>  drivers/net/ethernet/intel/igb/igb.h      |  2 ++
>  drivers/net/ethernet/intel/igb/igb_main.c | 12 +++++++++++-
>  2 files changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/intel/igb/igb.h
> b/drivers/net/ethernet/intel/igb/igb.h
> index 2d3daf022651..015b78144114 100644
> --- a/drivers/net/ethernet/intel/igb/igb.h
> +++ b/drivers/net/ethernet/intel/igb/igb.h
> @@ -664,6 +664,8 @@ struct igb_adapter {

Tested-by: Konrad Jankowski <konrad0.jankowski@xxxxxxxxx>