From: Phil Carmody <[email protected]> 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 <[email protected]> Reviewed-by: Paul Menage <[email protected]> Cc: Li Zefan <[email protected]> Acked-by: Kirill A. Shutemov <[email protected]> Cc: <[email protected]> Signed-off-by: Andrew Morton <[email protected]> --- kernel/cgroup.c | 14 ++++++-------- 1 file changed, 6 insertions(+), 8 deletions(-) diff -puN kernel/cgroup.c~cgroups-if-you-list_empty-a-head-then-dont-list_del-it kernel/cgroup.c --- a/kernel/cgroup.c~cgroups-if-you-list_empty-a-head-then-dont-list_del-it +++ a/kernel/cgroup.c @@ -1813,10 +1813,8 @@ int cgroup_attach_task(struct cgroup *cg /* 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_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 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); } _ _______________________________________________ stable mailing list [email protected] http://linux.kernel.org/mailman/listinfo/stable
