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]>
