idpf: Fix RSS LUT NULL ptr issue after soft reset

idpf: Fix RSS LUT NULL ptr issue after soft reset

[ Upstream commit ebecca5b093895da801b3eba1a55b4ec4027d196 ]

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 <sreedevi.joshi@intel.com>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Reviewed-by: Sridhar Samudrala <sridhar.samudrala@intel.com>
Reviewed-by: Emil Tantilov <emil.s.tantilov@intel.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Tested-by: Samuel Salin <Samuel.salin@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>