Messages in this thread | | | Subject | Re: [PATCH] ima: fix deadlock when traversing "ima_default_rules". | From | Mimi Zohar <> | Date | Thu, 30 Sep 2021 15:46:52 -0400 |
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Hi Liqiong,
On Sat, 2021-09-18 at 11:11 +0800, liqiong wrote: > 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. > > 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") > Signed-off-by: Mimi Zohar <zohar@linux.ibm.com> > Reported-by: kernel test robot <lkp@intel.com> > Fix sparse: incompatible types in comparison expression.
The "Fix sparse" line shouldn't be on a separate line. Either post the one line fix as a separate patch using the normal "Fixes:" tag or fix the "Reported-by" line, as previously suggested.
thanks,
Mimi
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