summaryrefslogtreecommitdiffstats
path: root/kernel/cgroup/cgroup.c
diff options
context:
space:
mode:
Diffstat (limited to 'kernel/cgroup/cgroup.c')
-rw-r--r--kernel/cgroup/cgroup.c25
1 files changed, 22 insertions, 3 deletions
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index a800c3b1b795..df71bffe9126 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -3643,6 +3643,12 @@ static ssize_t cgroup_pressure_write(struct kernfs_open_file *of, char *buf,
cgroup_get(cgrp);
cgroup_kn_unlock(of->kn);
+ /* Allow only one trigger per file descriptor */
+ if (ctx->psi.trigger) {
+ cgroup_put(cgrp);
+ return -EBUSY;
+ }
+
psi = cgroup_ino(cgrp) == 1 ? &psi_system : &cgrp->psi;
new = psi_trigger_create(psi, buf, nbytes, res);
if (IS_ERR(new)) {
@@ -3650,8 +3656,7 @@ static ssize_t cgroup_pressure_write(struct kernfs_open_file *of, char *buf,
return PTR_ERR(new);
}
- psi_trigger_replace(&ctx->psi.trigger, new);
-
+ smp_store_release(&ctx->psi.trigger, new);
cgroup_put(cgrp);
return nbytes;
@@ -3690,7 +3695,7 @@ static void cgroup_pressure_release(struct kernfs_open_file *of)
{
struct cgroup_file_ctx *ctx = of->priv;
- psi_trigger_replace(&ctx->psi.trigger, NULL);
+ psi_trigger_destroy(ctx->psi.trigger);
}
bool cgroup_psi_enabled(void)
@@ -6161,6 +6166,20 @@ static int cgroup_css_set_fork(struct kernel_clone_args *kargs)
if (ret)
goto err;
+ /*
+ * Spawning a task directly into a cgroup works by passing a file
+ * descriptor to the target cgroup directory. This can even be an O_PATH
+ * file descriptor. But it can never be a cgroup.procs file descriptor.
+ * This was done on purpose so spawning into a cgroup could be
+ * conceptualized as an atomic
+ *
+ * fd = openat(dfd_cgroup, "cgroup.procs", ...);
+ * write(fd, <child-pid>, ...);
+ *
+ * sequence, i.e. it's a shorthand for the caller opening and writing
+ * cgroup.procs of the cgroup indicated by @dfd_cgroup. This allows us
+ * to always use the caller's credentials.
+ */
ret = cgroup_attach_permissions(cset->dfl_cgrp, dst_cgrp, sb,
!(kargs->flags & CLONE_THREAD),
current->nsproxy->cgroup_ns);