The second tagged commit introduced a UAF, as it removed restoring
q_vector->vport pointers after reinitializating the structures.
This is due to that all queue allocation functions are performed here
with the new temporary vport structure and those functions rewrite
the backpointers to the vport. Then, this new struct is freed and
the pointers start leading to nowhere.

But generally speaking, the current logic is very fragile. It claims
to be more reliable when the system is low on memory, but in fact, it
consumes two times more memory as at the moment of running this
function, there are two vports allocated with their queues and vectors.
Moreover, it claims to prevent the driver from running into "bad state",
but in fact, any error during the rebuild leaves the old vport in the
partially allocated state.
Finally, if the interface is down when the function is called, it always
allocates a new queue set, but when the user decides to enable the
interface later on, vport_open() allocates them once again, IOW there's
a clear memory leak here.

Just don't allocate a new queue set when performing a reset, that solves
crashes and memory leaks. Readd the old queue number and reopen the
interface on rollback - that solves limbo states when the device is left
disabled and/or without HW queues enabled.

Fixes: 02cbfba1 ("idpf: add ethtool callbacks")
Fixes: e4891e46 ("idpf: split &idpf_queue into 4 strictly-typed queue structures")
Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Tested-by: Krishneil Singh <krishneil.k.singh@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Link: https://patch.msgid.link/20240806220923.3359860-2-anthony.l.nguyen@intel.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>