Re: [PATCH iwl-net v2 1/3] idpf: Fix RSS LUT NULL pointer crash on early ethtool operations

[Simon Horman <horms@kernel.org>]

On Mon, Nov 24, 2025 at 12:47:48PM -0600, Sreedevi Joshi wrote:
> The RSS LUT is not initialized until the interface comes up, causing
> the following NULL pointer crash when ethtool operations like rxhash on/off
> are performed before the interface is brought up for the first time.
> 
> Move RSS LUT initialization from ndo_open to vport creation to ensure LUT
> is always available. This enables RSS configuration via ethtool before
> bringing the interface up. Simplify LUT management by maintaining all
> changes in the driver's soft copy and programming zeros to the indirection
> table when rxhash is disabled. Defer HW programming until the interface
> comes up if it is down during rxhash and LUT configuration changes.
> 
> Steps to reproduce:
> ** Load idpf driver; interfaces will be created
> 	modprobe idpf
> ** Before bringing the interfaces up, turn rxhash off
> 	ethtool -K eth2 rxhash off
> 
> [89408.371875] BUG: kernel NULL pointer dereference, address: 0000000000000000
> [89408.371908] #PF: supervisor read access in kernel mode
> [89408.371924] #PF: error_code(0x0000) - not-present page
> [89408.371940] PGD 0 P4D 0
> [89408.371953] Oops: Oops: 0000 [#1] SMP NOPTI
> <snip>
> [89408.372052] RIP: 0010:memcpy_orig+0x16/0x130
> [89408.372310] Call Trace:
> [89408.372317]  <TASK>
> [89408.372326]  ? idpf_set_features+0xfc/0x180 [idpf]
> [89408.372363]  __netdev_update_features+0x295/0xde0
> [89408.372384]  ethnl_set_features+0x15e/0x460
> [89408.372406]  genl_family_rcv_msg_doit+0x11f/0x180
> [89408.372429]  genl_rcv_msg+0x1ad/0x2b0
> [89408.372446]  ? __pfx_ethnl_set_features+0x10/0x10
> [89408.372465]  ? __pfx_genl_rcv_msg+0x10/0x10
> [89408.372482]  netlink_rcv_skb+0x58/0x100
> [89408.372502]  genl_rcv+0x2c/0x50
> [89408.372516]  netlink_unicast+0x289/0x3e0
> [89408.372533]  netlink_sendmsg+0x215/0x440
> [89408.372551]  __sys_sendto+0x234/0x240
> [89408.372571]  __x64_sys_sendto+0x28/0x30
> [89408.372585]  x64_sys_call+0x1909/0x1da0
> [89408.372604]  do_syscall_64+0x7a/0xfa0
> [89408.373140]  ? clear_bhb_loop+0x60/0xb0
> [89408.373647]  entry_SYSCALL_64_after_hwframe+0x76/0x7e
> [89408.378887]  </TASK>
> <snip>
> 
> Fixes: a251eee62133 ("idpf: add SRIOV support and other ndo_ops")
> Signed-off-by: Sreedevi Joshi <sreedevi.joshi@intel.com>
> Reviewed-by: Sridhar Samudrala <sridhar.samudrala@intel.com>
> Reviewed-by: Emil Tantilov <emil.s.tantilov@intel.com>
> Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
> Reviewed-by: Paul Menzel <pmenzel@molgen.mpg.de>

Reviewed-by: Simon Horman <horms@kernel.org>