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authorAleksa Sarai <cyphar@cyphar.com>2015-06-09 21:32:09 +1000
committerTejun Heo <tj@kernel.org>2015-07-14 17:29:23 -0400
commit7e47682ea555e7c1edef1d8fd96e2aa4c12abe59 (patch)
tree6012cbc180ae7d633be4ed2ff1f1f6f7f188c1a0 /kernel/fork.c
parentd770e558e21961ad6cfdf0ff7df0eb5d7d4f0754 (diff)
downloadlinux-sh-7e47682ea555e7c1edef1d8fd96e2aa4c12abe59.tar.gz
cgroup: allow a cgroup subsystem to reject a fork
Add a new cgroup subsystem callback can_fork that conditionally states whether or not the fork is accepted or rejected by a cgroup policy. In addition, add a cancel_fork callback so that if an error occurs later in the forking process, any state modified by can_fork can be reverted. Allow for a private opaque pointer to be passed from cgroup_can_fork to cgroup_post_fork, allowing for the fork state to be stored by each subsystem separately. Also add a tagging system for cgroup_subsys.h to allow for CGROUP_<TAG> enumerations to be be defined and used. In addition, explicitly add a CGROUP_CANFORK_COUNT macro to make arrays easier to define. This is in preparation for implementing the pids cgroup subsystem. Signed-off-by: Aleksa Sarai <cyphar@cyphar.com> Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'kernel/fork.c')
-rw-r--r--kernel/fork.c17
1 files changed, 15 insertions, 2 deletions
diff --git a/kernel/fork.c b/kernel/fork.c
index 1bfefc6f96a4..40e3af12c55e 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1239,6 +1239,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
{
int retval;
struct task_struct *p;
+ void *cgrp_ss_priv[CGROUP_CANFORK_COUNT] = {};
if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
return ERR_PTR(-EINVAL);
@@ -1513,6 +1514,16 @@ static struct task_struct *copy_process(unsigned long clone_flags,
p->task_works = NULL;
/*
+ * Ensure that the cgroup subsystem policies allow the new process to be
+ * forked. It should be noted the the new process's css_set can be changed
+ * between here and cgroup_post_fork() if an organisation operation is in
+ * progress.
+ */
+ retval = cgroup_can_fork(p, cgrp_ss_priv);
+ if (retval)
+ goto bad_fork_free_pid;
+
+ /*
* Make it visible to the rest of the system, but dont wake it up yet.
* Need tasklist lock for parent etc handling!
*/
@@ -1548,7 +1559,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
spin_unlock(&current->sighand->siglock);
write_unlock_irq(&tasklist_lock);
retval = -ERESTARTNOINTR;
- goto bad_fork_free_pid;
+ goto bad_fork_cancel_cgroup;
}
if (likely(p->pid)) {
@@ -1590,7 +1601,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
write_unlock_irq(&tasklist_lock);
proc_fork_connector(p);
- cgroup_post_fork(p);
+ cgroup_post_fork(p, cgrp_ss_priv);
if (clone_flags & CLONE_THREAD)
threadgroup_change_end(current);
perf_event_fork(p);
@@ -1600,6 +1611,8 @@ static struct task_struct *copy_process(unsigned long clone_flags,
return p;
+bad_fork_cancel_cgroup:
+ cgroup_cancel_fork(p, cgrp_ss_priv);
bad_fork_free_pid:
if (pid != &init_struct_pid)
free_pid(pid);