device_cgroup: don't grab mutex in rcu callback (53eb8c82) · Commits · 戴 / test

Commit ("security/device_cgroup: lock assert fails in dev_exception_clean()") grabs devcgroup_mutex to fix assert failure, but a mutex can't be grabbed in rcu callback. Since there shouldn't be any other references when css_free is called, mutex isn't needed for list cleanup in devcgroup_css_free(). Signed-off-by:

Jerry Snitselaar <jerry.snitselaar@oracle.com> Acked-by:

Tejun Heo <tj@kernel.org> Acked-by:

Aristeu Rozanski <aris@redhat.com> Cc: James Morris <james.l.morris@oracle.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

security/device_cgroup.c

+12 −9

Original line number	Diff line number	Diff line
		@@ -159,6 +159,16 @@ static void dev_exception_rm(struct dev_cgroup *dev_cgroup,
		}
		}

		static void __dev_exception_clean(struct dev_cgroup *dev_cgroup)
		{
		struct dev_exception_item ex, tmp;

		list_for_each_entry_safe(ex, tmp, &dev_cgroup->exceptions, list) {
		list_del_rcu(&ex->list);
		kfree_rcu(ex, rcu);
		}
		}

		/**
		* dev_exception_clean - frees all entries of the exception list
		* @dev_cgroup: dev_cgroup with the exception list to be cleaned
		@@ -167,14 +177,9 @@ static void dev_exception_rm(struct dev_cgroup *dev_cgroup,
		*/
		static void dev_exception_clean(struct dev_cgroup *dev_cgroup)
		{
		struct dev_exception_item ex, tmp;

		lockdep_assert_held(&devcgroup_mutex);

		list_for_each_entry_safe(ex, tmp, &dev_cgroup->exceptions, list) {
		list_del_rcu(&ex->list);
		kfree_rcu(ex, rcu);
		}
		__dev_exception_clean(dev_cgroup);
		}

		/*
		@@ -215,9 +220,7 @@ static void devcgroup_css_free(struct cgroup *cgroup)
		struct dev_cgroup *dev_cgroup;

		dev_cgroup = cgroup_to_devcgroup(cgroup);
		mutex_lock(&devcgroup_mutex);
		dev_exception_clean(dev_cgroup);
		mutex_unlock(&devcgroup_mutex);
		__dev_exception_clean(dev_cgroup);
		kfree(dev_cgroup);
		}

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