On 2024/5/7 19:54, Mimi Zohar wrote:
On Tue, 2024-05-07 at 09:37 +0000, GUO Zihua wrote:
From: liqiong liqiong@nfschina.com
[ Upstream commit eb0782bbdfd0d7c4786216659277c3fd585afc0e ]
The current IMA ruleset is identified by the variable "ima_rules" that default to "&ima_default_rules". When loading a custom policy for the first time, the variable is updated to "&ima_policy_rules" instead. That update isn't RCU-safe, and deadlocks are possible. Indeed, some functions like ima_match_policy() may loop indefinitely when traversing "ima_default_rules" with list_for_each_entry_rcu().
When iterating over the default ruleset back to head, if the list head is "ima_default_rules", and "ima_rules" have been updated to "&ima_policy_rules", the loop condition (&entry->list != ima_rules) stays always true, traversing won't terminate, causing a soft lockup and RCU stalls.
Introduce a temporary value for "ima_rules" when iterating over the ruleset to avoid the deadlocks.
Addition:
A rcu_read_lock pair is added within ima_update_policy_flag to avoid suspicious RCU usage warning. This pair of RCU lock was added with commit 4f2946aa0c45 ("IMA: introduce a new policy option func=SETXATTR_CHECK") on mainstream.
Signed-off-by: liqiong liqiong@nfschina.com Reviewed-by: THOBY Simon Simon.THOBY@viveris.fr Fixes: 38d859f991f3 ("IMA: policy can now be updated multiple times") Reported-by: kernel test robot lkp@intel.com (Fix sparse: incompatible types in comparison expression.) Signed-off-by: Mimi Zohar zohar@linux.ibm.com Sig=ned-off-by: GUO Zihua guozihua@huawei.com
Hi Scott,
I'm confused by this patch. Is it meant for upstream?
thanks,
Mimi
It's a backport from upstream.