> -----Original Message-----
> From: Intel-wired-lan <[email protected]> On Behalf Of
> Simon Horman
> Sent: Thursday, November 27, 2025 3:45 AM
> To: Joshi, Sreedevi <[email protected]>
> Cc: [email protected]; [email protected]; Loktionov,
> Aleksandr <[email protected]>; Samudrala, Sridhar
> <[email protected]>; Tantilov, Emil S <[email protected]>
> Subject: Re: [Intel-wired-lan] [PATCH iwl-net v2 3/3] idpf: Fix RSS LUT NULL
> ptr
> issue after soft reset
>
> On Mon, Nov 24, 2025 at 12:47:50PM -0600, Sreedevi Joshi wrote:
> > During soft reset, the RSS LUT is freed and not restored unless the
> > interface is up. If an ethtool command that accesses the rss lut is
> > attempted immediately after reset, it will result in NULL ptr
> > dereference. Also, there is no need to reset the rss lut if the soft
> > reset does not involve queue count change.
> >
> > After soft reset, set the RSS LUT to default values based on the
> > updated queue count only if the reset was a result of a queue count
> > change and the LUT was not configured by the user. In all other cases,
> > don't touch the LUT.
> >
> > Steps to reproduce:
> >
> > ** Bring the interface down (if up)
> > ifconfig eth1 down
> >
> > ** update the queue count (eg., 27->20) ethtool -L eth1 combined 20
> >
> > ** display the RSS LUT
> > ethtool -x eth1
> >
> > [82375.558338] BUG: kernel NULL pointer dereference, address:
> > 0000000000000000 [82375.558373] #PF: supervisor read access in kernel
> > mode [82375.558391] #PF: error_code(0x0000) - not-present page
> > [82375.558408] PGD 0 P4D 0 [82375.558421] Oops: Oops: 0000 [#1] SMP
> > NOPTI <snip> [82375.558516] RIP: 0010:idpf_get_rxfh+0x108/0x150 [idpf]
> > [82375.558786] Call Trace:
> > [82375.558793] <TASK>
> > [82375.558804] rss_prepare.isra.0+0x187/0x2a0 [82375.558827]
> > rss_prepare_data+0x3a/0x50 [82375.558845]
> > ethnl_default_doit+0x13d/0x3e0 [82375.558863]
> > genl_family_rcv_msg_doit+0x11f/0x180
> > [82375.558886] genl_rcv_msg+0x1ad/0x2b0 [82375.558902] ?
> > __pfx_ethnl_default_doit+0x10/0x10
> > [82375.558920] ? __pfx_genl_rcv_msg+0x10/0x10 [82375.558937]
> > netlink_rcv_skb+0x58/0x100 [82375.558957] genl_rcv+0x2c/0x50
> > [82375.558971] netlink_unicast+0x289/0x3e0 [82375.558988]
> > netlink_sendmsg+0x215/0x440 [82375.559005]
> __sys_sendto+0x234/0x240
> > [82375.559555] __x64_sys_sendto+0x28/0x30 [82375.560068]
> > x64_sys_call+0x1909/0x1da0 [82375.560576] do_syscall_64+0x7a/0xfa0
> > [82375.561076] ? clear_bhb_loop+0x60/0xb0 [82375.561567]
> > entry_SYSCALL_64_after_hwframe+0x76/0x7e
> > <snip>
> >
> > Fixes: 02cbfba1add5 ("idpf: add ethtool callbacks")
> > Signed-off-by: Sreedevi Joshi <[email protected]>
> > Reviewed-by: Aleksandr Loktionov <[email protected]>
> > Reviewed-by: Sridhar Samudrala <[email protected]>
> > Reviewed-by: Emil Tantilov <[email protected]>
>
> Reviewed-by: Simon Horman <[email protected]>
Tested-by: Samuel Salin <[email protected]>
