Restricts the mounting of tmpfs:
mount -t tmpfs -o memcg=<cgroup>
Only if the mounting task is allowed to open <cgroup>/cgroup.procs file
and allowed to enter the cgroup. Thus, processes are allowed to direct
tmpfs changes to a cgroup that they themselves can enter and allocate
memory in.
Signed-off-by: Mina Almasry <almasrymina@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Theodore Ts'o <tytso@xxxxxxx>
Cc: Greg Thelen <gthelen@xxxxxxxxxx>
Cc: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Roman Gushchin <songmuchun@xxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Cc: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Cc: riel@xxxxxxxxxxx
Cc: linux-mm@xxxxxxxxx
Cc: linux-fsdevel@xxxxxxxxxxxxxxx
Cc: cgroups@xxxxxxxxxxxxxxx
---
mm/memcontrol.c | 26 +++++++++++++++++++++++++-
1 file changed, 25 insertions(+), 1 deletion(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 389d2f2be9674..2e4c20d09f959 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -62,6 +62,7 @@
#include <linux/tracehook.h>
#include <linux/psi.h>
#include <linux/seq_buf.h>
+#include <linux/string.h>
#include "internal.h"
#include <net/sock.h>
#include <net/ip.h>
@@ -2585,9 +2586,32 @@ void mem_cgroup_handle_over_high(void)
*/
struct mem_cgroup *mem_cgroup_get_from_path(const char *path)
{
- struct file *file;
+ static const char procs_filename[] = "/cgroup.procs";
+ struct file *file, *procs;
struct cgroup_subsys_state *css;
struct mem_cgroup *memcg;
+ char *procs_path =
+ kmalloc(strlen(path) + sizeof(procs_filename), GFP_KERNEL);
+
+ if (procs_path == NULL)
+ return ERR_PTR(-ENOMEM);
+ strcpy(procs_path, path);
+ strcat(procs_path, procs_filename);
+
+ procs = filp_open(procs_path, O_WRONLY, 0);
+ kfree(procs_path);
+
+ /*
+ * Restrict the capability for tasks to mount with memcg charging to the
+ * cgroup they could not join. For example, disallow:
+ *
+ * mount -t tmpfs -o memcg=root-cgroup nodev <MOUNT_DIR>
+ *
+ * if it is a non-root task.
+ */
+ if (IS_ERR(procs))
+ return (struct mem_cgroup *)procs;
+ fput(procs);
file = filp_open(path, O_DIRECTORY | O_RDONLY, 0);
if (IS_ERR(file))
--
2.34.0.rc0.344.g81b53c2807-goog
