[lxc-devel] [PATCH 6/9] Add attach.[ch]: Helper functions for lxc-attach
Christian Seiler
christian at iwakd.de
Thu Feb 9 14:33:12 UTC 2012
The following helper functions for lxc-attach are added to a new file
attach.c:
- lxc_proc_get_context_info: Get cgroup memberships, personality and
capability bounding set from /proc for a given process.
- lxc_proc_free_context_info: Free the data structure responsible
- lxc_attach_proc_to_cgroups: Add the process specified by the pid
parameter to the cgroups given by the ctx parameter.
- lxc_attach_drop_privs: Drop capabilities to the capability mask given in
the ctx parameter.
---
src/lxc/Makefile.am | 4 +-
src/lxc/attach.c | 247 +++++++++++++++++++++++++++++++++++++++++++++++++++
src/lxc/attach.h | 47 ++++++++++
3 files changed, 297 insertions(+), 1 deletions(-)
create mode 100644 src/lxc/attach.c
create mode 100644 src/lxc/attach.h
diff --git a/src/lxc/Makefile.am b/src/lxc/Makefile.am
index 924cf1d..e695883 100644
--- a/src/lxc/Makefile.am
+++ b/src/lxc/Makefile.am
@@ -12,7 +12,8 @@ pkginclude_HEADERS = \
conf.h \
list.h \
log.h \
- state.h
+ state.h \
+ attach.h
sodir=$(libdir)
# use PROGRAMS to avoid complains from automake
@@ -41,6 +42,7 @@ liblxc_so_SOURCES = \
list.h \
state.c state.h \
log.c log.h \
+ attach.c attach.h \
\
network.c network.h \
nl.c nl.h \
diff --git a/src/lxc/attach.c b/src/lxc/attach.c
new file mode 100644
index 0000000..9392116
--- /dev/null
+++ b/src/lxc/attach.c
@@ -0,0 +1,247 @@
+/*
+ * lxc: linux Container library
+ *
+ * (C) Copyright IBM Corp. 2007, 2008
+ *
+ * Authors:
+ * Daniel Lezcano <dlezcano at fr.ibm.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#define _GNU_SOURCE
+#include <unistd.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/param.h>
+#include <sys/prctl.h>
+
+#if !HAVE_DECL_PR_CAPBSET_DROP
+#define PR_CAPBSET_DROP 24
+#endif
+
+#include "namespace.h"
+#include "log.h"
+#include "attach.h"
+#include "caps.h"
+#include "cgroup.h"
+#include "config.h"
+
+#include "setns.h"
+
+lxc_log_define(lxc_attach, lxc);
+
+int setns(int fd, int nstype)
+{
+#ifndef __NR_setns
+ errno = ENOSYS;
+ return -1;
+#else
+ return syscall(__NR_setns, fd, nstype);
+#endif
+}
+
+struct lxc_proc_context_info *lxc_proc_get_context_info(pid_t pid)
+{
+ struct lxc_proc_context_info *info = calloc(1, sizeof(*info));
+ FILE *proc_file;
+ char proc_fn[MAXPATHLEN];
+ char *line = NULL, *ptr, *ptr2;
+ size_t line_bufsz = 0;
+ int ret, found, l;
+ int i;
+
+ if (!info) {
+ SYSERROR("Could not allocate memory.");
+ return NULL;
+ }
+
+ /* read capabilities */
+ snprintf(proc_fn, MAXPATHLEN, "/proc/%d/status", pid);
+
+ proc_file = fopen(proc_fn, "r");
+ if (!proc_file) {
+ SYSERROR("Could not open %s", proc_fn);
+ goto out_error;
+ }
+
+ found = 0;
+ while (getline(&line, &line_bufsz, proc_file) != -1) {
+ ret = sscanf(line, "CapBnd: %llx", &info->capability_mask);
+ if (ret != EOF && ret > 0) {
+ found = 1;
+ break;
+ }
+ }
+
+ fclose(proc_file);
+
+ if (!found) {
+ SYSERROR("Could not read capability bounding set from %s", proc_fn);
+ errno = ENOENT;
+ goto out_error;
+ }
+
+ /* read personality */
+ snprintf(proc_fn, MAXPATHLEN, "/proc/%d/personality", pid);
+
+ proc_file = fopen(proc_fn, "r");
+ if (!proc_file) {
+ SYSERROR("Could not open %s", proc_fn);
+ goto out_error;
+ }
+
+ ret = fscanf(proc_file, "%lx", &info->personality);
+ fclose(proc_file);
+
+ if (ret == EOF || ret == 0) {
+ SYSERROR("Could not read personality from %s", proc_fn);
+ errno = ENOENT;
+ goto out_error;
+ }
+
+ /* read cgroups */
+ snprintf(proc_fn, MAXPATHLEN, "/proc/%d/cgroup", pid);
+
+ proc_file = fopen(proc_fn, "r");
+ if (!proc_file) {
+ SYSERROR("Could not open %s", proc_fn);
+ goto out_error;
+ }
+
+ /* we don't really know how many cgroup subsystems there are
+ * mounted, so we go through the whole file twice */
+ i = 0;
+ while (getline(&line, &line_bufsz, proc_file) != -1) {
+ /* we assume that all lines containing at least two colons
+ * are valid */
+ ptr = strchr(line, ':');
+ if (ptr && strchr(ptr + 1, ':'))
+ i++;
+ }
+
+ rewind(proc_file);
+
+ info->cgroups = calloc(i, sizeof(*(info->cgroups)));
+ info->cgroups_count = i;
+
+ i = 0;
+ while (getline(&line, &line_bufsz, proc_file) != -1 && i < info->cgroups_count) {
+ /* format of the lines is:
+ * id:subsystems:path, where subsystems are separated by
+ * commas and each subsystem may also be of the form
+ * name=xxx if it describes a private named hierarchy
+ * we will ignore the id in the following */
+ ptr = strchr(line, ':');
+ ptr2 = ptr ? strchr(ptr + 1, ':') : NULL;
+
+ /* ignore invalid lines */
+ if (!ptr || !ptr2) continue;
+
+ l = strlen(ptr2) - 1;
+ if (ptr2[l] == '\n')
+ ptr2[l] = '\0';
+
+ info->cgroups[i].subsystems = strndup(ptr + 1, ptr2 - (ptr + 1));
+ info->cgroups[i].cgroup = strdup(ptr2 + 1);
+
+ i++;
+ }
+
+ free(line);
+ fclose(proc_file);
+
+ return info;
+
+out_error:
+ lxc_proc_free_context_info(info);
+ free(line);
+ return NULL;
+}
+
+void lxc_proc_free_context_info(struct lxc_proc_context_info *info)
+{
+ if (!info)
+ return;
+
+ if (info->cgroups) {
+ int i;
+ for (i = 0; i < info->cgroups_count; i++) {
+ free(info->cgroups[i].subsystems);
+ free(info->cgroups[i].cgroup);
+ }
+ }
+ free(info->cgroups);
+ free(info);
+}
+
+int lxc_attach_proc_to_cgroups(pid_t pid, struct lxc_proc_context_info *ctx)
+{
+ int i, ret;
+
+ if (!ctx) {
+ ERROR("No valid context supplied when asked to attach "
+ "process to cgroups.");
+ return -1;
+ }
+
+ for (i = 0; i < ctx->cgroups_count; i++) {
+ char *path;
+
+ /* the kernel should return paths that start with '/' */
+ if (ctx->cgroups[i].cgroup[0] != '/') {
+ ERROR("For cgroup subsystem(s) %s the path '%s' does "
+ "not start with a '/'",
+ ctx->cgroups[i].subsystems,
+ ctx->cgroups[i].cgroup);
+ return -1;
+ }
+
+ /* lxc_cgroup_path_get can process multiple subsystems */
+ ret = lxc_cgroup_path_get(&path, ctx->cgroups[i].subsystems,
+ &ctx->cgroups[i].cgroup[1]);
+ if (ret)
+ return -1;
+
+ ret = lxc_cgroup_attach(path, pid);
+ if (ret)
+ return -1;
+ }
+
+ return 0;
+}
+
+int lxc_attach_drop_privs(struct lxc_proc_context_info *ctx)
+{
+ int last_cap = lxc_caps_last_cap();
+ int cap;
+
+ for (cap = 0; cap <= last_cap; cap++) {
+ if (ctx->capability_mask & (1LL << cap))
+ continue;
+
+ if (prctl(PR_CAPBSET_DROP, cap, 0, 0, 0)) {
+ SYSERROR("failed to remove capability id %d", cap);
+ return -1;
+ }
+ }
+
+ return 0;
+}
+
+
diff --git a/src/lxc/attach.h b/src/lxc/attach.h
new file mode 100644
index 0000000..7e67455
--- /dev/null
+++ b/src/lxc/attach.h
@@ -0,0 +1,47 @@
+/*
+ * lxc: linux Container library
+ *
+ * (C) Copyright IBM Corp. 2007, 2008
+ *
+ * Authors:
+ * Daniel Lezcano <dlezcano at fr.ibm.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#ifndef _attach_h
+#define _attach_h
+
+#include <sys/types.h>
+
+struct lxc_proc_cgroup_info {
+ char *subsystems;
+ char *cgroup;
+};
+
+struct lxc_proc_context_info {
+ unsigned long personality;
+ unsigned long long capability_mask;
+ struct lxc_proc_cgroup_info* cgroups;
+ int cgroups_count;
+};
+
+extern struct lxc_proc_context_info *lxc_proc_get_context_info(pid_t pid);
+extern void lxc_proc_free_context_info(struct lxc_proc_context_info *info);
+
+extern int lxc_attach_proc_to_cgroups(pid_t pid, struct lxc_proc_context_info *ctx);
+extern int lxc_attach_drop_privs(struct lxc_proc_context_info *ctx);
+
+#endif
--
1.7.2.5
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