eth: nfp: bound the ntuple rule dump by the caller's buffer size

nfp_net_get_fs_loc() dumps every entry of nn->fs.list into rule_locs[]
without consulting cmd->rule_cnt, which is how many entries the caller
had room for.  ETHTOOL_GRXCLSRLALL requires no CAP_NET_ADMIN and the
ioctl sizes the buffer from the rule_cnt userspace passes in, so once an
admin has installed flow steering rules any user can ask for fewer slots
than there are rules and run off the end of the allocation.  A rule_cnt
of 0 leaves the buffer pointer NULL and the walk dereferences it.

Bail out with -EMSGSIZE when the buffer fills up, the way the other
ntuple capable drivers do, and report how many locations were filled so
a shrinking rule list does not leave the caller reading stale slots.

Reported-by: VEGA <vega@nebusec.ai>
Fixes: 9eb03bb1c035 ("nfp: add ethtool flow steering callbacks")
Reviewed-by: Joe Damato <joe@dama.to>
Link: https://patch.msgid.link/20260903032611.3000029-3-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

0 files changed, 0 insertions, 0 deletions