CHROMIUM: remove Android's cgroup generic permissions checks

The implementation is utterly broken, resulting in all processes being
allows to move tasks between sets (as long as they have access to the
"tasks" attribute), and upstream is heading towards checking only
capability anyway, so let's get rid of this code.

BUG=b:31790445,chromium:647994
TEST=Boot android container, examine logcat

Change-Id: I2f780a5992c34e52a8f2d0b3557fc9d490da2779
Signed-off-by: Dmitry Torokhov <dtor@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/394967
Reviewed-by: Ricky Zhou <rickyz@chromium.org>
Reviewed-by: John Stultz <john.stultz@linaro.org>

diff --git a/Documentation/cgroups/cgroups.txt b/Documentation/cgroups/cgroups.txt
index 2d984e20783be198586267633e65a842ae61559e..c6256ae9885b8ac7445f6d10066ee541ebb388b8 100644 (file)
--- a/Documentation/cgroups/cgroups.txt
+++ b/Documentation/cgroups/cgroups.txt
@@ -578,15 +578,6 @@ is completely unused; @cgrp->parent is still valid. (Note - can also
 be called for a newly-created cgroup if an error occurs after this
 subsystem's create() method has been called for the new cgroup).
 
-int allow_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
-(cgroup_mutex held by caller)
-
-Called prior to moving a task into a cgroup; if the subsystem
-returns an error, this will abort the attach operation.  Used
-to extend the permission checks - if all subsystems in a cgroup
-return 0, the attach will be allowed to proceed, even if the
-default permission check (root or same user) fails.
-
 int can_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
 (cgroup_mutex held by caller)
 

diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
index 4a4eea01956c108e43f849ce27a27dc2582d9ce4..06b77f9dd3f2052ac87f970b8aa8c195b78f7ada 100644 (file)
--- a/include/linux/cgroup-defs.h
+++ b/include/linux/cgroup-defs.h
@@ -422,7 +422,6 @@ struct cgroup_subsys {
        void (*css_reset)(struct cgroup_subsys_state *css);
        void (*css_e_css_changed)(struct cgroup_subsys_state *css);
 
-       int (*allow_attach)(struct cgroup_taskset *tset);
        int (*can_attach)(struct cgroup_taskset *tset);
        void (*cancel_attach)(struct cgroup_taskset *tset);
        void (*attach)(struct cgroup_taskset *tset);

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 70358b9f5a7ab809be0dd1e6d5310c7588166ba7..cb91b44f5f7877d5899403b26ca1d9231c1ac9b6 100644 (file)
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -528,16 +528,6 @@ static inline void pr_cont_cgroup_path(struct cgroup *cgrp)
        pr_cont_kernfs_path(cgrp->kn);
 }
 
-/*
- * Default Android check for whether the current process is allowed to move a
- * task across cgroups, either because CAP_SYS_NICE is set or because the uid
- * of the calling process is the same as the moved task or because we are
- * running as root.
- * Returns 0 if this is allowed, or -EACCES otherwise.
- */
-int subsys_cgroup_allow_attach(struct cgroup_taskset *tset);
-
-
 #else /* !CONFIG_CGROUPS */
 
 struct cgroup_subsys_state;
@@ -562,10 +552,6 @@ static inline void cgroup_free(struct task_struct *p) {}
 static inline int cgroup_init_early(void) { return 0; }
 static inline int cgroup_init(void) { return 0; }
 
-static inline int subsys_cgroup_allow_attach(void *tset)
-{
-       return -EINVAL;
-}
 #endif /* !CONFIG_CGROUPS */
 
 #endif /* _LINUX_CGROUP_H */

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index bd541053efc2cfae451d53d4f10d4751dc4af85d..371ee5a827e007a3cf4299c050cca8f6857fbd0c 100644 (file)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2663,45 +2663,6 @@ static int cgroup_attach_task(struct cgroup *dst_cgrp,
        return ret;
 }
 
-int subsys_cgroup_allow_attach(struct cgroup_taskset *tset)
-{
-       const struct cred *cred = current_cred(), *tcred;
-       struct task_struct *task;
-       struct cgroup_subsys_state *css;
-
-       if (capable(CAP_SYS_NICE))
-               return 0;
-
-       cgroup_taskset_for_each(task, css, tset) {
-               tcred = __task_cred(task);
-
-               if (current != task && !uid_eq(cred->euid, tcred->uid) &&
-                   !uid_eq(cred->euid, tcred->suid))
-                       return -EACCES;
-       }
-
-       return 0;
-}
-
-static int cgroup_allow_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
-{
-       struct cgroup_subsys_state *css;
-       int i;
-       int ret;
-
-       for_each_css(css, i, cgrp) {
-               if (css->ss->allow_attach) {
-                       ret = css->ss->allow_attach(tset);
-                       if (ret)
-                               return ret;
-               } else {
-                       return -EACCES;
-               }
-       }
-
-       return 0;
-}
-
 static int cgroup_procs_write_permission(struct task_struct *task,
                                         struct cgroup *dst_cgrp,
                                         struct kernfs_open_file *of)
@@ -2716,24 +2677,8 @@ static int cgroup_procs_write_permission(struct task_struct *task,
         */
        if (!uid_eq(cred->euid, GLOBAL_ROOT_UID) &&
            !uid_eq(cred->euid, tcred->uid) &&
-           !uid_eq(cred->euid, tcred->suid)) {
-               /*
-                * if the default permission check fails, give each
-                * cgroup a chance to extend the permission check
-                */
-               struct cgroup_taskset tset = {
-                       .src_csets = LIST_HEAD_INIT(tset.src_csets),
-                       .dst_csets = LIST_HEAD_INIT(tset.dst_csets),
-                       .csets = &tset.src_csets,
-               };
-               struct css_set *cset;
-               cset = task_css_set(task);
-               list_add(&cset->mg_node, &tset.src_csets);
-               ret = cgroup_allow_attach(dst_cgrp, &tset);
-               list_del(&tset.src_csets);
-               if (ret)
-                       ret = -EACCES;
-       }
+           !uid_eq(cred->euid, tcred->suid))
+               ret = -EACCES;
 
        if (!ret && cgroup_on_dfl(dst_cgrp)) {
                struct super_block *sb = of->file->f_path.dentry->d_sb;

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index c90bfb620981e9822ec2fd0d0ab6a6cd12086d80..471094bfbcc6e1f0fa28b3585596d577986223bb 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -8935,7 +8935,6 @@ struct cgroup_subsys cpu_cgrp_subsys = {
        .fork           = cpu_cgroup_fork,
        .can_attach     = cpu_cgroup_can_attach,
        .attach         = cpu_cgroup_attach,
-       .allow_attach   = subsys_cgroup_allow_attach,
        .legacy_cftypes = cpu_files,
        .early_init     = 1,
 };

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 5c714f33f49477f66f70377e60a8e5930dbcb753..ee6acd279953f9a7378ad68c547a3b47307c657c 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4879,11 +4879,6 @@ static int mem_cgroup_can_attach(struct cgroup_taskset *tset)
        return ret;
 }
 
-static int mem_cgroup_allow_attach(struct cgroup_taskset *tset)
-{
-       return subsys_cgroup_allow_attach(tset);
-}
-
 static void mem_cgroup_cancel_attach(struct cgroup_taskset *tset)
 {
        if (mc.to)
@@ -5045,10 +5040,6 @@ static int mem_cgroup_can_attach(struct cgroup_taskset *tset)
 {
        return 0;
 }
-static int mem_cgroup_allow_attach(struct cgroup_taskset *tset)
-{
-       return 0;
-}
 static void mem_cgroup_cancel_attach(struct cgroup_taskset *tset)
 {
 }
@@ -5232,7 +5223,6 @@ struct cgroup_subsys memory_cgrp_subsys = {
        .can_attach = mem_cgroup_can_attach,
        .cancel_attach = mem_cgroup_cancel_attach,
        .attach = mem_cgroup_move_task,
-       .allow_attach = mem_cgroup_allow_attach,
        .bind = mem_cgroup_bind,
        .dfl_cftypes = memory_files,
        .legacy_cftypes = mem_cgroup_legacy_files,