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[libvirt] [PATCH v3 05/12] LXC: Creating devices for container on host side



user namespace doesn't allow to create devices in
uninit userns. We should create devices on host side.

We first mount tmpfs on dev directroy under state dir
of container. then create devices under this dev dir.

Finally in container, mount the dev directroy created
on host to the /dev/ directroy of container.

Signed-off-by: Gao feng <gaofeng cn fujitsu com>
---
 src/lxc/lxc_container.c  |  96 +++++++++++++---------------------
 src/lxc/lxc_controller.c | 130 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 166 insertions(+), 60 deletions(-)

diff --git a/src/lxc/lxc_container.c b/src/lxc/lxc_container.c
index 52fcf39..c647f8e 100644
--- a/src/lxc/lxc_container.c
+++ b/src/lxc/lxc_container.c
@@ -683,7 +683,7 @@ err:
 }
 
 
-static int lxcContainerMountBasicFS(char *sec_mount_options)
+static int lxcContainerMountBasicFS(void)
 {
     const struct {
         const char *src;
@@ -711,8 +711,6 @@ static int lxcContainerMountBasicFS(char *sec_mount_options)
     int i, rc = -1;
     char *opts = NULL;
 
-    VIR_DEBUG("Mounting basic filesystems sec_mount_options=%s", sec_mount_options);
-
     for (i = 0; i < ARRAY_CARDINALITY(mnts); i++) {
         const char *srcpath = NULL;
 
@@ -750,26 +748,6 @@ static int lxcContainerMountBasicFS(char *sec_mount_options)
         }
     }
 
-    /*
-     * tmpfs is limited to 64kb, since we only have device nodes in there
-     * and don't want to DOS the entire OS RAM usage
-     */
-
-    if (virAsprintf(&opts,
-                    "mode=755,size=65536%s", sec_mount_options) < 0) {
-        virReportOOMError();
-        goto cleanup;
-    }
-
-    VIR_DEBUG("Mount devfs on /dev type=tmpfs flags=%x, opts=%s",
-              MS_NOSUID, opts);
-    if (mount("devfs", "/dev", "tmpfs", MS_NOSUID, opts) < 0) {
-        virReportSystemError(errno,
-                             _("Failed to mount %s on %s type %s (%s)"),
-                             "devfs", "/dev", "tmpfs", opts);
-        goto cleanup;
-    }
-
     rc = 0;
 
 cleanup:
@@ -811,6 +789,33 @@ static int lxcContainerMountProcFuse(virDomainDefPtr def ATTRIBUTE_UNUSED,
 }
 #endif
 
+static int lxcContainerMountFSDev(virDomainDefPtr def,
+                                  const char *stateDir)
+{
+    int ret;
+    char *path = NULL;
+
+    VIR_DEBUG("Mount /dev/ stateDir=%s", stateDir);
+
+    if ((ret = virAsprintf(&path,
+                           "/.oldroot/%s/%s.dev",
+                           stateDir,
+                           def->name)) < 0)
+        return ret;
+
+    VIR_DEBUG("Trying to move %s to /dev", path);
+
+    if ((ret = mount(path, "/dev",
+                     NULL, MS_MOVE, NULL)) < 0) {
+        virReportSystemError(errno,
+                             _("Failed to mount %s on /dev"),
+                             path);
+    }
+
+    VIR_FREE(path);
+    return ret;
+}
+
 static int lxcContainerMountFSDevPTS(virDomainDefPtr def,
                                      const char *stateDir)
 {
@@ -847,22 +852,10 @@ cleanup:
     return ret;
 }
 
-static int lxcContainerPopulateDevices(char **ttyPaths, size_t nttyPaths)
+static int lxcContainerSetupDevices(char **ttyPaths, size_t nttyPaths)
 {
     size_t i;
     const struct {
-        int maj;
-        int min;
-        mode_t mode;
-        const char *path;
-    } devs[] = {
-        { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_NULL, 0666, "/dev/null" },
-        { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_ZERO, 0666, "/dev/zero" },
-        { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_FULL, 0666, "/dev/full" },
-        { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_RANDOM, 0666, "/dev/random" },
-        { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_URANDOM, 0666, "/dev/urandom" },
-    };
-    const struct {
         const char *src;
         const char *dst;
     } links[] = {
@@ -872,18 +865,6 @@ static int lxcContainerPopulateDevices(char **ttyPaths, size_t nttyPaths)
         { "/proc/self/fd", "/dev/fd" },
     };
 
-    /* Populate /dev/ with a few important bits */
-    for (i = 0; i < ARRAY_CARDINALITY(devs); i++) {
-        dev_t dev = makedev(devs[i].maj, devs[i].min);
-        if (mknod(devs[i].path, S_IFCHR, dev) < 0 ||
-            chmod(devs[i].path, devs[i].mode)) {
-            virReportSystemError(errno,
-                                 _("Failed to make device %s"),
-                                 devs[i].path);
-            return -1;
-        }
-    }
-
     for (i = 0; i < ARRAY_CARDINALITY(links); i++) {
         if (symlink(links[i].src, links[i].dst) < 0) {
             virReportSystemError(errno,
@@ -903,15 +884,6 @@ static int lxcContainerPopulateDevices(char **ttyPaths, size_t nttyPaths)
                                  _("Failed to bind /dev/pts/ptmx on to /dev/ptmx"));
             return -1;
         }
-    } else {
-        /* Legacy devpts, so we need to just use shared one */
-        dev_t dev = makedev(LXC_DEV_MAJ_TTY, LXC_DEV_MIN_PTMX);
-        if (mknod("/dev/ptmx", S_IFCHR, dev) < 0 ||
-            chmod("/dev/ptmx", 0666)) {
-            virReportSystemError(errno, "%s",
-                                 _("Failed to make device /dev/ptmx"));
-            return -1;
-        }
     }
 
     for (i = 0; i < nttyPaths; i++) {
@@ -1813,7 +1785,7 @@ static int lxcContainerSetupPivotRoot(virDomainDefPtr vmDef,
         goto cleanup;
 
     /* Mounts the core /proc, /sys, etc filesystems */
-    if (lxcContainerMountBasicFS(sec_mount_options) < 0)
+    if (lxcContainerMountBasicFS() < 0)
         goto cleanup;
 
     /* Mounts /proc/meminfo etc sysinfo */
@@ -1825,12 +1797,16 @@ static int lxcContainerSetupPivotRoot(virDomainDefPtr vmDef,
     if (virCgroupIsolateMount(cgroup, "/.oldroot/", sec_mount_options) < 0)
         goto cleanup;
 
+    /* Mounts /dev */
+    if (lxcContainerMountFSDev(vmDef, stateDir) < 0)
+        goto cleanup;
+
     /* Mounts /dev/pts */
     if (lxcContainerMountFSDevPTS(vmDef, stateDir) < 0)
         goto cleanup;
 
-    /* Populates device nodes in /dev/ */
-    if (lxcContainerPopulateDevices(ttyPaths, nttyPaths) < 0)
+    /* Setup device nodes in /dev/ */
+    if (lxcContainerSetupDevices(ttyPaths, nttyPaths) < 0)
         goto cleanup;
 
     /* Sets up any non-root mounts from guest config */
diff --git a/src/lxc/lxc_controller.c b/src/lxc/lxc_controller.c
index 0a2e3ac..e9808f3 100644
--- a/src/lxc/lxc_controller.c
+++ b/src/lxc/lxc_controller.c
@@ -1184,6 +1184,132 @@ cleanup:
 }
 
 
+static int
+virLXCControllerSetupDev(virLXCControllerPtr ctrl)
+{
+    char *mount_options = NULL;
+    char *opts = NULL;
+    char *dev = NULL;
+    int ret = -1;
+
+    VIR_DEBUG("Setting up /dev/ for container");
+
+    mount_options = virSecurityManagerGetMountOptions(ctrl->securityManager,
+                                                      ctrl->def);
+
+    if (virAsprintf(&dev, "/%s/%s.dev",
+                    LXC_STATE_DIR, ctrl->def->name) < 0) {
+        virReportOOMError();
+        goto cleanup;
+    }
+
+    if (virFileMakePath(dev) < 0) {
+        virReportSystemError(errno,
+                             _("Failed to make path %s"),
+                             dev);
+        goto cleanup;
+    }
+
+    /*
+     * tmpfs is limited to 64kb, since we only have device nodes in there
+     * and don't want to DOS the entire OS RAM usage
+     */
+
+    if (virAsprintf(&opts,
+                    "mode=755,size=65536%s", mount_options) < 0) {
+        virReportOOMError();
+        goto cleanup;
+    }
+
+
+    VIR_DEBUG("Mount devfs on %s type=tmpfs flags=%x, opts=%s",
+              dev, MS_NOSUID, opts);
+    if (mount("devfs", dev, "tmpfs", MS_NOSUID, opts) < 0) {
+        virReportSystemError(errno,
+                             _("Failed to mount devfs (%s) on %s"),
+                             opts, dev);
+        goto cleanup;
+    }
+
+    ret = 0;
+
+cleanup:
+    VIR_FREE(opts);
+    VIR_FREE(mount_options);
+    VIR_FREE(dev);
+    return ret;
+}
+
+
+static int virLXCControllerPopulateDevices(virLXCControllerPtr ctrl)
+{
+    size_t i;
+    int ret = -1;
+    char *ptmx = NULL;
+    char *path = NULL;
+    const struct {
+        int maj;
+        int min;
+        mode_t mode;
+        const char *path;
+    } devs[] = {
+        { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_NULL, 0666, "/null" },
+        { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_ZERO, 0666, "/zero" },
+        { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_FULL, 0666, "/full" },
+        { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_RANDOM, 0666, "/random" },
+        { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_URANDOM, 0666, "/urandom" },
+    };
+
+    if (virLXCControllerSetupDev(ctrl) < 0)
+        goto out;
+
+    /* Populate /dev/ with a few important bits */
+    for (i = 0 ; i < ARRAY_CARDINALITY(devs) ; i++) {
+        if (virAsprintf(&path, "/%s/%s.dev/%s",
+                        LXC_STATE_DIR, ctrl->def->name,
+                        devs[i].path) < 0) {
+            virReportOOMError();
+            goto out;
+        }
+
+        dev_t dev = makedev(devs[i].maj, devs[i].min);
+        if (mknod(path, S_IFCHR, dev) < 0 ||
+            chmod(path, devs[i].mode)) {
+            virReportSystemError(errno,
+                                 _("Failed to make device %s"),
+                                 devs[i].path);
+            goto out;
+        }
+        VIR_FREE(path);
+    }
+
+    if (virAsprintf(&ptmx, "/%s/%s.devpts/ptmx",
+                    LXC_STATE_DIR, ctrl->def->name) < 0) {
+        virReportOOMError();
+        goto out;
+    }
+
+    if (access(ptmx, W_OK)) {
+        if (virAsprintf(&path, "/%s/%s.dev/ptmx",
+                        LXC_STATE_DIR, ctrl->def->name)) {
+            virReportOOMError();
+            goto out;
+        }
+        /* Legacy devpts, so we need to just use shared one */
+        dev_t dev = makedev(LXC_DEV_MAJ_TTY, LXC_DEV_MIN_PTMX);
+        if (mknod(path, S_IFCHR, dev) < 0 ||
+            chmod(path, 0666)) {
+            virReportSystemError(errno,  _("Failed to make device %s"), path);
+            goto out;
+        }
+    }
+
+    ret = 0;
+out:
+    VIR_FREE(ptmx);
+    VIR_FREE(path);
+    return ret;
+}
 
 /**
  * virLXCControllerMoveInterfaces
@@ -1585,6 +1711,9 @@ virLXCControllerRun(virLXCControllerPtr ctrl)
     if (virLXCControllerSetupDevPTS(ctrl) < 0)
         goto cleanup;
 
+    if (virLXCControllerPopulateDevices(ctrl) < 0)
+        goto cleanup;
+
     if (virLXCControllerSetupFuse(ctrl) < 0)
         goto cleanup;
 
@@ -1609,6 +1738,7 @@ virLXCControllerRun(virLXCControllerPtr ctrl)
     if (virLXCControllerSetupUserns(ctrl) < 0)
         goto cleanup;
 
+
     if (virLXCControllerMoveInterfaces(ctrl) < 0)
         goto cleanup;
 
-- 
1.8.1.4


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