i40e: Add checking for null for nlmsg_find_attr()

stable inclusion
from stable-v5.10.169
commit b452e20b95d7e0b09ee4a6f773e3ebe6764ff1cf
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7V9QX

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b452e20b95d7e0b09ee4a6f773e3ebe6764ff1cf



----------------------------------------------------

[ Upstream commit 7fa0b526 ]

The result of nlmsg_find_attr() 'br_spec' is dereferenced in
nla_for_each_nested(), but it can take NULL value in nla_find() function,
which will result in an error.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 51616018 ("i40e: Add support for getlink, setlink ndo ops")
Signed-off-by: Natalia Petrova <n.petrova@fintech.ru>
Reviewed-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Gurucharan G <gurucharanx.g@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Link: https://lore.kernel.org/r/20230209172833.3596034-1-anthony.l.nguyen@intel.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: zhaoxiaoqiang11 <zhaoxiaoqiang11@jd.com>