[systemd-devel] [PATCH] Do not clear parent mount flags when setting up namespaces

[Dave Reisner]

On Thu, Jan 01, 2015 at 04:49:04PM +0200, Topi Miettinen wrote:
> Copy parent directory mount flags when setting up a namespace and
> don't accidentally clear mount flags later.
> 
> Signed-off-by: Topi Miettinen <toiwoton at gmail.com>
> ---
>  src/core/namespace.c |  4 ++--
>  src/shared/util.c    | 20 ++++++++++++++++++--
>  src/shared/util.h    |  2 ++
>  3 files changed, 22 insertions(+), 4 deletions(-)
> 
> diff --git a/src/core/namespace.c b/src/core/namespace.c
> index 5b408e0..400bc50 100644
> --- a/src/core/namespace.c
> +++ b/src/core/namespace.c
> @@ -159,7 +159,7 @@ static int mount_dev(BindMount *m) {
>  
>          dev = strappenda(temporary_mount, "/dev");
>          (void)mkdir(dev, 0755);
> -        if (mount("tmpfs", dev, "tmpfs", MS_NOSUID|MS_STRICTATIME, "mode=755") < 0) {
> +        if (mount("tmpfs", dev, "tmpfs", get_mount_flags("/dev")|MS_NOSUID|MS_STRICTATIME, "mode=755") < 0) {
>                  r = -errno;
>                  goto fail;
>          }
> @@ -282,7 +282,7 @@ static int mount_kdbus(BindMount *m) {
>  
>          root = strappenda(temporary_mount, "/kdbus");
>          (void)mkdir(root, 0755);
> -        if (mount("tmpfs", root, "tmpfs", MS_NOSUID|MS_STRICTATIME, "mode=777") < 0) {
> +        if (mount("tmpfs", root, "tmpfs", get_mount_flags("/kdbus")|MS_NOSUID|MS_STRICTATIME, "mode=777") < 0) {

Shouldn't this be /sys/fs/bus/kdbus? We certainly don't mount kdbusfs in
the root...

>                  r = -errno;
>                  goto fail;
>          }
> diff --git a/src/shared/util.c b/src/shared/util.c
> index dfaf7f7..31fbb68 100644
> --- a/src/shared/util.c
> +++ b/src/shared/util.c
> @@ -61,6 +61,7 @@
>  #include <sys/personality.h>
>  #include <sys/xattr.h>
>  #include <libgen.h>
> +#include <sys/statvfs.h>
>  #undef basename
>  
>  #ifdef HAVE_SYS_AUXV_H
> @@ -6858,6 +6859,16 @@ int umount_recursive(const char *prefix, int flags) {
>          return r ? r : n;
>  }
>  
> +unsigned long get_mount_flags(const char *path)
> +{

Reigning style says to put the opening { at the end of the first line.

> +        struct statvfs buf;
> +
> +        if (statvfs(path, &buf) < 0)
> +                return 0;
> +
> +        return buf.f_flag;
> +}
> +
>  int bind_remount_recursive(const char *prefix, bool ro) {
>          _cleanup_set_free_free_ Set *done = NULL;
>          _cleanup_free_ char *cleaned = NULL;
> @@ -6892,6 +6903,7 @@ int bind_remount_recursive(const char *prefix, bool ro) {
>                  _cleanup_set_free_free_ Set *todo = NULL;
>                  bool top_autofs = false;
>                  char *x;
> +                unsigned long orig_flags;
>  
>                  todo = set_new(&string_hash_ops);
>                  if (!todo)
> @@ -6969,7 +6981,9 @@ int bind_remount_recursive(const char *prefix, bool ro) {
>                          if (mount(cleaned, cleaned, NULL, MS_BIND|MS_REC, NULL) < 0)
>                                  return -errno;
>  
> -                        if (mount(NULL, prefix, NULL, MS_BIND|MS_REMOUNT|(ro ? MS_RDONLY : 0), NULL) < 0)
> +                        orig_flags = get_mount_flags(prefix);
> +                        orig_flags &= ~MS_RDONLY;
> +                        if (mount(NULL, prefix, NULL, orig_flags|MS_BIND|MS_REMOUNT|(ro ? MS_RDONLY : 0), NULL) < 0)
>                                  return -errno;
>  
>                          x = strdup(cleaned);
> @@ -6989,7 +7003,9 @@ int bind_remount_recursive(const char *prefix, bool ro) {
>                          if (r < 0)
>                                  return r;
>  
> -                        if (mount(NULL, x, NULL, MS_BIND|MS_REMOUNT|(ro ? MS_RDONLY : 0), NULL) < 0) {
> +                        orig_flags = get_mount_flags(x);
> +                        orig_flags &= ~MS_RDONLY;
> +                        if (mount(NULL, x, NULL, orig_flags|MS_BIND|MS_REMOUNT|(ro ? MS_RDONLY : 0), NULL) < 0) {
>  
>                                  /* Deal with mount points that are
>                                   * obstructed by a later mount */
> diff --git a/src/shared/util.h b/src/shared/util.h
> index a131a3c..4b3070a 100644
> --- a/src/shared/util.h
> +++ b/src/shared/util.h
> @@ -1021,6 +1021,8 @@ union file_handle_union {
>  
>  int update_reboot_param_file(const char *param);
>  
> +unsigned long get_mount_flags(const char *path);
> +
>  int umount_recursive(const char *target, int flags);
>  
>  int bind_remount_recursive(const char *prefix, bool ro);
> -- 
> 2.1.4
> 
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