cgroups: rework base cgroup parsing

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

diff --git a/src/lxc/cgroups/cgfsng.c b/src/lxc/cgroups/cgfsng.c
index d0652b8fc3cc8a03c41118730c72329eb53a5ae1..6d7504e7e2748e96a06b54130a3d8c4f603f68fa 100644 (file)
--- a/src/lxc/cgroups/cgfsng.c
+++ b/src/lxc/cgroups/cgfsng.c
@@ -46,6 +46,7 @@
 #include "memory_utils.h"
 #include "mount_utils.h"
 #include "storage/storage.h"
+#include "string_utils.h"
 #include "syscall_wrappers.h"
 #include "utils.h"
 
@@ -695,24 +696,33 @@ static struct hierarchy *add_hierarchy(struct cgroup_ops *ops,
                                       char **clist, char *mountpoint,
                                       char *container_base_path, int type)
 {
-       struct hierarchy *new;
+       __do_free struct hierarchy *new = NULL;
        int newentry;
 
+       if (abspath(container_base_path))
+               return syserrno(NULL, "Container base path must be relative to controller mount");
+
        new = zalloc(sizeof(*new));
        if (!new)
                return ret_set_errno(NULL, ENOMEM);
 
-       new->controllers = clist;
-       new->mountpoint = mountpoint;
-       new->container_base_path = container_base_path;
-       new->version = type;
-       new->cgfd_con = -EBADF;
-       new->cgfd_limit = -EBADF;
-       new->cgfd_mon = -EBADF;
+       new->version                    = type;
+       new->controllers                = clist;
+       new->mountpoint                 = mountpoint;
+       new->container_base_path        = container_base_path;
+       new->cgfd_con                   = -EBADF;
+       new->cgfd_limit                 = -EBADF;
+       new->cgfd_mon                   = -EBADF;
+
+       TRACE("Adding cgroup hierarchy with mountpoint %s and base cgroup %s %s",
+             mountpoint, container_base_path,
+             clist ? "with controllers " : "without any controllers");
+       for (char *const *it = clist; it && *it; it++)
+               TRACE("%s", *it);
 
        newentry = append_null_to_list((void ***)&ops->hierarchies);
        (ops->hierarchies)[newentry] = new;
-       return new;
+       return move_ptr(new);
 }
 
 /* Get a copy of the mountpoint from @line, which is a line from
@@ -790,38 +800,71 @@ static bool controller_in_clist(char *cgline, char *c)
        return false;
 }
 
+static inline char *trim(char *s)
+{
+       size_t len;
+
+       len = strlen(s);
+       while ((len > 1) && (s[len - 1] == '\n'))
+               s[--len] = '\0';
+
+       return s;
+}
+
 /* @basecginfo is a copy of /proc/$$/cgroup. Return the current cgroup for
  * @controller.
  */
-static char *cg_hybrid_get_current_cgroup(char *basecginfo, char *controller,
-                                         int type)
+static char *cg_hybrid_get_current_cgroup(bool relative, char *basecginfo,
+                                         char *controller, int type)
 {
-       char *p = basecginfo;
+       char *base_cgroup = basecginfo;
 
        for (;;) {
                bool is_cgv2_base_cgroup = false;
 
                /* cgroup v2 entry in "/proc/<pid>/cgroup": "0::/some/path" */
-               if ((type == CGROUP2_SUPER_MAGIC) && (*p == '0'))
+               if ((type == CGROUP2_SUPER_MAGIC) && (*base_cgroup == '0'))
                        is_cgv2_base_cgroup = true;
 
-               p = strchr(p, ':');
-               if (!p)
+               base_cgroup = strchr(base_cgroup, ':');
+               if (!base_cgroup)
                        return NULL;
-               p++;
+               base_cgroup++;
+
+               if (is_cgv2_base_cgroup || (controller && controller_in_clist(base_cgroup, controller))) {
+                       __do_free char *copy = NULL;
 
-               if (is_cgv2_base_cgroup || (controller && controller_in_clist(p, controller))) {
-                       p = strchr(p, ':');
-                       if (!p)
+                       base_cgroup = strchr(base_cgroup, ':');
+                       if (!base_cgroup)
                                return NULL;
-                       p++;
-                       return copy_to_eol(p);
+                       base_cgroup++;
+
+                       copy = copy_to_eol(base_cgroup);
+                       if (!copy)
+                               return NULL;
+                       trim(copy);
+
+                       if (!relative) {
+                               base_cgroup = prune_init_scope(copy);
+                               if (!base_cgroup)
+                                       return NULL;
+                       } else {
+                               base_cgroup = copy;
+                       }
+
+                       if (abspath(base_cgroup))
+                               base_cgroup = deabs(base_cgroup);
+
+                       if (is_empty_string(base_cgroup))
+                               base_cgroup = ".";
+
+                       return strdup(base_cgroup);
                }
 
-               p = strchr(p, '\n');
-               if (!p)
+               base_cgroup = strchr(base_cgroup, '\n');
+               if (!base_cgroup)
                        return NULL;
-               p++;
+               base_cgroup++;
        }
 }
 
@@ -879,17 +922,6 @@ static int get_existing_subsystems(char ***klist, char ***nlist)
        return 0;
 }
 
-static char *trim(char *s)
-{
-       size_t len;
-
-       len = strlen(s);
-       while ((len > 1) && (s[len - 1] == '\n'))
-               s[--len] = '\0';
-
-       return s;
-}
-
 static void lxc_cgfsng_print_hierarchies(struct cgroup_ops *ops)
 {
        int i;
@@ -3384,16 +3416,14 @@ static int cg_hybrid_init(struct cgroup_ops *ops, bool relative, bool unprivileg
                }
 
                if (type == CGROUP_SUPER_MAGIC)
-                       base_cgroup = cg_hybrid_get_current_cgroup(basecginfo, controller_list[0], CGROUP_SUPER_MAGIC);
+                       base_cgroup = cg_hybrid_get_current_cgroup(relative, basecginfo, controller_list[0], CGROUP_SUPER_MAGIC);
                else
-                       base_cgroup = cg_hybrid_get_current_cgroup(basecginfo, NULL, CGROUP2_SUPER_MAGIC);
+                       base_cgroup = cg_hybrid_get_current_cgroup(relative, basecginfo, NULL, CGROUP2_SUPER_MAGIC);
                if (!base_cgroup) {
                        WARN("Failed to find current cgroup");
                        continue;
                }
 
-               trim(base_cgroup);
-               prune_init_scope(base_cgroup);
                if (type == CGROUP2_SUPER_MAGIC)
                        writeable = test_writeable_v2(mountpoint, base_cgroup);
                else
@@ -3450,8 +3480,7 @@ static int cg_hybrid_init(struct cgroup_ops *ops, bool relative, bool unprivileg
 /* Get current cgroup from /proc/self/cgroup for the cgroupfs v2 hierarchy. */
 static char *cg_unified_get_current_cgroup(bool relative)
 {
-       __do_free char *basecginfo = NULL;
-       char *copy;
+       __do_free char *basecginfo = NULL, *copy = NULL;
        char *base_cgroup;
 
        if (!relative && (geteuid() == 0))
@@ -3469,8 +3498,23 @@ static char *cg_unified_get_current_cgroup(bool relative)
        copy = copy_to_eol(base_cgroup);
        if (!copy)
                return NULL;
+       trim(copy);
+
+       if (!relative) {
+               base_cgroup = prune_init_scope(copy);
+               if (!base_cgroup)
+                       return NULL;
+       } else {
+               base_cgroup = copy;
+       }
+
+       if (abspath(base_cgroup))
+               base_cgroup = deabs(base_cgroup);
+
+       if (is_empty_string(base_cgroup))
+               base_cgroup = ".";
 
-       return trim(copy);
+       return strdup(base_cgroup);
 }
 
 static int cg_unified_init(struct cgroup_ops *ops, bool relative,
@@ -3483,8 +3527,6 @@ static int cg_unified_init(struct cgroup_ops *ops, bool relative,
        base_cgroup = cg_unified_get_current_cgroup(relative);
        if (!base_cgroup)
                return ret_errno(EINVAL);
-       if (!relative)
-               prune_init_scope(base_cgroup);
 
        /*
         * We assume that the cgroup we're currently in has been delegated to

diff --git a/src/lxc/cgroups/cgroup.c b/src/lxc/cgroups/cgroup.c
index 874cdf5789d6e04c42ce7f4e0d54e2cf1f36e190..1350e78c0a3ab5d8a06f129d22b169cb2ca0e091 100644 (file)
--- a/src/lxc/cgroups/cgroup.c
+++ b/src/lxc/cgroups/cgroup.c
@@ -98,21 +98,13 @@ void cgroup_exit(struct cgroup_ops *ops)
 }
 
 #define INIT_SCOPE "/init.scope"
-void prune_init_scope(char *cg)
+char *prune_init_scope(char *cg)
 {
-       char *point;
+       if (is_empty_string(cg))
+               return NULL;
 
-       if (!cg)
-               return;
-
-       point = cg + strlen(cg) - strlen(INIT_SCOPE);
-       if (point < cg)
-               return;
+       if (strnequal(cg, INIT_SCOPE, STRLITERALLEN(INIT_SCOPE)))
+               return cg + STRLITERALLEN(INIT_SCOPE);
 
-       if (strequal(point, INIT_SCOPE)) {
-               if (point == cg)
-                       *(point + 1) = '\0';
-               else
-                       *point = '\0';
-       }
+       return cg;
 }

diff --git a/src/lxc/cgroups/cgroup.h b/src/lxc/cgroups/cgroup.h
index 6901e0b3740379b31f2139b690fefd1f809f4740..f8060c06df126d00225544e06ac45d4c2de63040 100644 (file)
--- a/src/lxc/cgroups/cgroup.h
+++ b/src/lxc/cgroups/cgroup.h
@@ -204,7 +204,7 @@ __hidden extern struct cgroup_ops *cgroup_init(struct lxc_conf *conf);
 __hidden extern void cgroup_exit(struct cgroup_ops *ops);
 define_cleanup_function(struct cgroup_ops *, cgroup_exit);
 
-__hidden extern void prune_init_scope(char *cg);
+__hidden extern char *prune_init_scope(char *cg);
 
 __hidden extern int cgroup_attach(const struct lxc_conf *conf, const char *name,
                                  const char *lxcpath, pid_t pid);

diff --git a/src/lxc/string_utils.h b/src/lxc/string_utils.h
index 6cf23d186425aee0d4ca722bbeff0ecd0e779090..85962c76dc08febc817c6c0424b8de9480e8e162 100644 (file)
--- a/src/lxc/string_utils.h
+++ b/src/lxc/string_utils.h
@@ -150,6 +150,11 @@ static inline bool abspath(const char *str)
        return *str == '/';
 }
 
+static inline char *deabs(char *str)
+{
+       return str + strspn(str, "/");
+}
+
 #define strnprintf(buf, buf_size, ...)                                            \
        ({                                                                        \
                int __ret_strnprintf;                                             \