On 2022/12/16 11:04, Paul Moore wrote:
On Thu, Dec 15, 2022 at 9:36 PM Guozihua (Scott) guozihua@huawei.com wrote:
On 2022/12/16 5:04, Paul Moore wrote:
...
How bad is the backport really? Perhaps it is worth doing it to see what it looks like?
It might not be that bad, I'll try to post a version next Monday.
Thanks for giving it a shot.
When I am trying a partial backport of b16942455193 ("ima: use the lsm policy update notifier"), I took a closer look into it and if we rip off the RCU and the notifier part, there would be a potential UAF issue when multiple processes are calling ima_lsm_update_rule() and ima_match_rules() at the same time. ima_lsm_update_rule() would free the old rule if the new rule is successfully copied and initialized, leading to ima_match_rules() accessing a freed rule.
To reserve the mainline solution, we would have to either introduce RCU for rule access, which would work better with notifier mechanism or the same rule would be updated multiple times, or we would have to introduce a lock for LSM based rule update.