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| author | Phil Carmody <ext-phil.2.carmody@nokia.com> | 2011-03-22 16:30:13 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2011-03-22 17:43:58 -0700 |
| commit | 8d2587970b8bdf7c8d9208e3f4bb93182aef1a0f (patch) | |
| tree | 931cacaa98583412975b4601b62fb244a5ed678d /kernel | |
| parent | edd45544c6f09550df0a5491aa8a07af24767e73 (diff) | |
| download | lwn-8d2587970b8bdf7c8d9208e3f4bb93182aef1a0f.tar.gz lwn-8d2587970b8bdf7c8d9208e3f4bb93182aef1a0f.zip | |
cgroups: if you list_empty() a head then don't list_del() it
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@nokia.com>
Reviewed-by: Paul Menage <menage@google.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Kirill A. Shutemov <kirill@shutemov.name>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/cgroup.c | 14 |
1 files changed, 6 insertions, 8 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 95362d15128c..e31b220a743d 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 @@ -4241,7 +4239,7 @@ 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); } |