[12/24] proc: Add fs_context support to procfs [ver #7]
Andrei Vagin
avagin at virtuozzo.com
Tue Jun 26 07:27:38 UTC 2018
On Mon, Jun 25, 2018 at 11:13:20PM -0700, Andrei Vagin wrote:
> On Mon, Jun 18, 2018 at 08:34:50PM -0700, Andrei Vagin wrote:
> > Hi David,
> >
> > We run CRIU tests for vfs/for-next, and today a few of these test failed. I
> > found that the problem appears after this patch..
> >
> > > int pid_ns_prepare_proc(struct pid_namespace *ns)
> > > {
> > > + struct proc_fs_context *ctx;
> > > + struct fs_context *fc;
> > > struct vfsmount *mnt;
> > > + int ret;
> > > +
> > > + fc = vfs_new_fs_context(&proc_fs_type, NULL, 0,
> > > + FS_CONTEXT_FOR_KERNEL_MOUNT);
> > > + if (IS_ERR(fc))
> > > + return PTR_ERR(fc);
> > > +
> > > + ctx = container_of(fc, struct proc_fs_context, fc);
> > > + if (ctx->pid_ns != ns) {
> > > + put_pid_ns(ctx->pid_ns);
> > > + get_pid_ns(ns);
> > > + ctx->pid_ns = ns;
> > > + }
> > > +
> > > + ret = vfs_get_tree(fc);
> > > + if (ret < 0) {
> > > + put_fs_context(fc);
> > > + return ret;
> > > + }
> > >
> > > - mnt = kern_mount_data(&proc_fs_type, ns, 0);
>
> Here ns->user_ns and get_current_cred()->user_ns are not always equal
What do you think about the attached patch?
>
> > > + mnt = vfs_create_mount(fc);
> > > + put_fs_context(fc);
> > > if (IS_ERR(mnt))
> > > return PTR_ERR(mnt);
> > >
>
> > #define _GNU_SOURCE
> > #include <sys/types.h>
> > #include <sched.h>
> > #include <unistd.h>
> > #include <stdio.h>
> > #include <sys/mount.h>
> > #include <sys/wait.h>
> > #include <sys/stat.h>
> > #include <fcntl.h>
> > #include <stdlib.h>
> > #include <grp.h>
> > #include <linux/limits.h>
> >
> >
> > #define NS_STACK_SIZE 4096
> >
> > #define __stack_aligned__ __attribute__((aligned(16)))
> >
> > /* All arguments should be above stack, because it grows down */
> > struct ns_exec_args {
> > char stack[NS_STACK_SIZE] __stack_aligned__;
> > char stack_ptr[0];
> > int pfd[2];
> > };
> >
> > static int ns_exec(void *_arg)
> > {
> > struct ns_exec_args *args = (struct ns_exec_args *) _arg;
> > int ret;
> >
> > close(args->pfd[1]);
> > if (read(args->pfd[0], &ret, sizeof(ret)) != sizeof(ret))
> > return -1;
> >
> > setsid();
> >
> > if (setuid(0) || setgid(0) || setgroups(0, NULL)) {
> > fprintf(stderr, "set*id failed: %m\n");
> > return -1;
> > }
> >
> > if (mount("proc", "/mnt", "proc", MS_MGC_VAL | MS_NOSUID | MS_NOEXEC | MS_NODEV, NULL)) {
> > fprintf(stderr, "mount(/proc) failed: %m\n");
> > return -1;
> > }
> >
> > return 0;
> > }
> >
> > #define UID_MAP "0 100000 100000\n100000 200000 50000"
> > #define GID_MAP "0 400000 50000\n50000 500000 100000"
> > int main()
> > {
> > pid_t pid;
> > int ret, status;
> > struct ns_exec_args args;
> > int flags;
> > char pname[PATH_MAX];
> > int fd, pfd[2];
> >
> > if (pipe(pfd))
> > return 1;
> >
> > args.pfd[0] = pfd[0];
> > args.pfd[1] = pfd[1];
> >
> > flags = CLONE_NEWPID | CLONE_NEWNS | CLONE_NEWUTS |
> > CLONE_NEWNET | CLONE_NEWIPC | CLONE_NEWUSER | SIGCHLD;
> >
> > pid = clone(ns_exec, args.stack_ptr, flags, &args);
> > if (pid < 0) {
> > fprintf(stderr, "clone() failed: %m\n");
> > exit(1);
> > }
> >
> >
> > snprintf(pname, sizeof(pname), "/proc/%d/uid_map", pid);
> > fd = open(pname, O_WRONLY);
> > if (fd < 0) {
> > fprintf(stderr, "open(%s): %m\n", pname);
> > exit(1);
> > }
> > if (write(fd, UID_MAP, sizeof(UID_MAP)) < 0) {
> > fprintf(stderr, "write(" UID_MAP "): %m\n");
> > exit(1);
> > }
> > close(fd);
> >
> > snprintf(pname, sizeof(pname), "/proc/%d/gid_map", pid);
> > fd = open(pname, O_WRONLY);
> > if (fd < 0) {
> > fprintf(stderr, "open(%s): %m\n", pname);
> > exit(1);
> > }
> > if (write(fd, GID_MAP, sizeof(GID_MAP)) < 0) {
> > fprintf(stderr, "write(" GID_MAP "): %m\n");
> > exit(1);
> > }
> > close(fd);
> >
> > if (write(pfd[1], &ret, sizeof(ret)) != sizeof(ret))
> > return 1;
> >
> > if (waitpid(pid, &status, 0) != pid)
> > return 1;
> > if (status)
> > return 1;
> >
> > return 0;
> > }
>
-------------- next part --------------
diff --git a/fs/fs_context.c b/fs/fs_context.c
index 97e8c1dc4e3b..ad2db7504031 100644
--- a/fs/fs_context.c
+++ b/fs/fs_context.c
@@ -235,10 +235,11 @@ EXPORT_SYMBOL(generic_parse_monolithic);
* another superblock (referred to by @reference) is supplied, may have
* parameters such as namespaces copied across from that superblock.
*/
-struct fs_context *vfs_new_fs_context(struct file_system_type *fs_type,
+struct fs_context *vfs_new_fs_context_userns(struct file_system_type *fs_type,
struct dentry *reference,
unsigned int sb_flags,
- enum fs_context_purpose purpose)
+ enum fs_context_purpose purpose,
+ struct user_namespace *user_ns)
{
struct fs_context *fc;
int ret;
@@ -259,7 +260,7 @@ struct fs_context *vfs_new_fs_context(struct file_system_type *fs_type,
fc->sb_flags |= SB_KERNMOUNT;
/* Fallthrough */
case FS_CONTEXT_FOR_USER_MOUNT:
- fc->user_ns = get_user_ns(fc->cred->user_ns);
+ fc->user_ns = get_user_ns(user_ns ? : fc->cred->user_ns);
fc->net_ns = get_net(current->nsproxy->net_ns);
break;
case FS_CONTEXT_FOR_SUBMOUNT:
diff --git a/fs/proc/root.c b/fs/proc/root.c
index efbdc08a3c86..c832d67067d9 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -298,8 +298,8 @@ int pid_ns_prepare_proc(struct pid_namespace *ns)
struct vfsmount *mnt;
int ret;
- fc = vfs_new_fs_context(&proc_fs_type, NULL, 0,
- FS_CONTEXT_FOR_KERNEL_MOUNT);
+ fc = vfs_new_fs_context_userns(&proc_fs_type, NULL, 0,
+ FS_CONTEXT_FOR_KERNEL_MOUNT, ns->user_ns);
if (IS_ERR(fc))
return PTR_ERR(fc);
diff --git a/include/linux/fs_context.h b/include/linux/fs_context.h
index 04ea338ff490..283212cda1ff 100644
--- a/include/linux/fs_context.h
+++ b/include/linux/fs_context.h
@@ -92,10 +92,19 @@ struct fs_context_operations {
/*
* fs_context manipulation functions.
*/
-extern struct fs_context *vfs_new_fs_context(struct file_system_type *fs_type,
+extern struct fs_context *vfs_new_fs_context_userns(struct file_system_type *fs_type,
struct dentry *reference,
unsigned int ms_flags,
- enum fs_context_purpose purpose);
+ enum fs_context_purpose purpose,
+ struct user_namespace *user_ns);
+static inline struct fs_context *vfs_new_fs_context(struct file_system_type *fs_type,
+ struct dentry *reference,
+ unsigned int ms_flags,
+ enum fs_context_purpose purpose)
+{
+ return vfs_new_fs_context_userns(fs_type, reference, ms_flags, purpose, NULL);
+}
+
extern struct fs_context *vfs_sb_reconfig(struct path *path, unsigned int ms_flags);
extern struct fs_context *vfs_dup_fs_context(struct fs_context *src);
extern int vfs_set_fs_source(struct fs_context *fc, const char *source, size_t len);
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