list_del() leaves poison in the prev and next pointers. The next
list_empty() will compare those poisons, and say the list isn't empty.
Any list operations that assume the node is on a list because of such a
check will be fooled into dereferencing poison. One needs to INIT the
node after the del, and fortunately there's already a wrapper for that -
list_del_init().
Some of the dels are followed by deallocations, so can be ignored,
and one can be merged with an add to make a move. Apart from that, I
erred on the side of caution in making nodes list_empty()-queriable.
Signed-off-by: Phil Carmody <ext-phil.2.carmody@xxxxxxxxx>
---
kernel/cgroup.c | 14 ++++++--------
1 files changed, 6 insertions(+), 8 deletions(-)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index b24d702..bcc7336 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1813,10 +1813,8 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
/* Update the css_set linked lists if we're using them */
write_lock(&css_set_lock);
- if (!list_empty(&tsk->cg_list)) {
- list_del(&tsk->cg_list);
- list_add(&tsk->cg_list, &newcg->tasks);
- }
+ if (!list_empty(&tsk->cg_list))
+ list_move(&tsk->cg_list, &newcg->tasks);
write_unlock(&css_set_lock);
for_each_subsys(root, ss) {
@@ -3655,12 +3653,12 @@ again:
spin_lock(&release_list_lock);
set_bit(CGRP_REMOVED, &cgrp->flags);
if (!list_empty(&cgrp->release_list))
- list_del(&cgrp->release_list);
+ list_del_init(&cgrp->release_list);
spin_unlock(&release_list_lock);
cgroup_lock_hierarchy(cgrp->root);
/* delete this cgroup from parent->children */
- list_del(&cgrp->sibling);
+ list_del_init(&cgrp->sibling);
cgroup_unlock_hierarchy(cgrp->root);
d = dget(cgrp->dentry);
@@ -3879,7 +3877,7 @@ void cgroup_unload_subsys(struct cgroup_subsys *ss)
subsys[ss->subsys_id] = NULL;
/* remove subsystem from rootnode's list of subsystems */
- list_del(&ss->sibling);
+ list_del_init(&ss->sibling);
/*
* disentangle the css from all css_sets attached to the dummytop. as
@@ -4253,7 +4251,7 @@ void cgroup_exit(struct task_struct *tsk, int run_callbacks)
if (!list_empty(&tsk->cg_list)) {
write_lock(&css_set_lock);
if (!list_empty(&tsk->cg_list))
- list_del(&tsk->cg_list);
+ list_del_init(&tsk->cg_list);
write_unlock(&css_set_lock);
}
--
1.7.2.rc1.37.gf8c40
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