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Groups > linux.kernel > #1385293

[PATCH v3 16/21] fs: Allow superblock owner to access do_remount_sb()

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Superblock level remounts are currently restricted to global
CAP_SYS_ADMIN, as is the path for changing the root mount to
read only on umount. Loosen both of these permission checks to
also allow CAP_SYS_ADMIN in any namespace which is privileged
towards the userns which originally mounted the filesystem.

Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
---
 fs/namespace.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index 0ad8e4a4f50b..575e3f8b34fd 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1510,7 +1510,7 @@ static int do_umount(struct mount *mnt, int flags)
 		 * Special case for "unmounting" root ...
 		 * we just try to remount it readonly.
 		 */
-		if (!capable(CAP_SYS_ADMIN))
+		if (!ns_capable(sb->s_user_ns, CAP_SYS_ADMIN))
 			return -EPERM;
 		down_write(&sb->s_umount);
 		if (!(sb->s_flags & MS_RDONLY))
@@ -2207,7 +2207,7 @@ static int do_remount(struct path *path, int flags, int mnt_flags,
 	down_write(&sb->s_umount);
 	if (flags & MS_BIND)
 		err = change_mount_flags(path->mnt, flags);
-	else if (!capable(CAP_SYS_ADMIN))
+	else if (!ns_capable(sb->s_user_ns, CAP_SYS_ADMIN))
 		err = -EPERM;
 	else
 		err = do_remount_sb(sb, flags, data, 0);
-- 
1.9.1

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[PATCH v3 00/21] Support fuse mounts in user namespaces Seth Forshee <seth.forshee@canonical.com> - 2016-04-22 17:40 +0200
  [PATCH v3 17/21] capabilities: Allow privileged user in s_user_ns to set security.* xattrs Seth Forshee <seth.forshee@canonical.com> - 2016-04-22 17:40 +0200
  [PATCH v3 01/21] fs: fix a posible leak of allocated superblock Seth Forshee <seth.forshee@canonical.com> - 2016-04-22 17:40 +0200
  [PATCH v3 15/21] fs: Don't remove suid for CAP_FSETID in s_user_ns Seth Forshee <seth.forshee@canonical.com> - 2016-04-22 17:40 +0200
  [PATCH v3 16/21] fs: Allow superblock owner to access do_remount_sb() Seth Forshee <seth.forshee@canonical.com> - 2016-04-22 17:50 +0200
  [PATCH v3 05/21] block_dev: Check permissions towards block device inode when mounting Seth Forshee <seth.forshee@canonical.com> - 2016-04-22 17:50 +0200
  [PATCH v3 04/21] block_dev: Support checking inode permissions in lookup_bdev() Seth Forshee <seth.forshee@canonical.com> - 2016-04-22 17:50 +0200
  [PATCH v3 12/21] fs: Refuse uid/gid changes which don't map into s_user_ns Seth Forshee <seth.forshee@canonical.com> - 2016-04-22 17:50 +0200
  [PATCH v3 14/21] fs: Allow superblock owner to change ownership of inodes with unmappable ids Seth Forshee <seth.forshee@canonical.com> - 2016-04-22 17:50 +0200
    Re: [PATCH v3 14/21] fs: Allow superblock owner to change ownership  of inodes with unmappable ids "Serge E. Hallyn" <serge@hallyn.com> - 2016-04-25 22:40 +0200
      Re: [PATCH v3 14/21] fs: Allow superblock owner to change ownership  of inodes with unmappable ids Seth Forshee <seth.forshee@canonical.com> - 2016-04-26 21:50 +0200
  [PATCH v3 11/21] cred: Reject inodes with invalid ids in set_create_file_as() Seth Forshee <seth.forshee@canonical.com> - 2016-04-22 17:50 +0200
  [PATCH v3 19/21] fuse: Support fuse filesystems outside of init_user_ns Seth Forshee <seth.forshee@canonical.com> - 2016-04-22 17:50 +0200
  [PATCH v3 21/21] fuse: Allow user namespace mounts Seth Forshee <seth.forshee@canonical.com> - 2016-04-22 17:50 +0200
  [PATCH v3 20/21] fuse: Restrict allow_other to the superblock's namespace or a descendant Seth Forshee <seth.forshee@canonical.com> - 2016-04-22 17:50 +0200
  [PATCH v3 10/21] fs: Check for invalid i_uid in may_follow_link() Seth Forshee <seth.forshee@canonical.com> - 2016-04-22 17:50 +0200
  [PATCH v3 09/21] Smack: Handle labels consistently in untrusted mounts Seth Forshee <seth.forshee@canonical.com> - 2016-04-22 17:50 +0200
  [PATCH v3 18/21] fuse: Add support for pid namespaces Seth Forshee <seth.forshee@canonical.com> - 2016-04-22 17:50 +0200
  [PATCH v3 08/21] userns: Replace in_userns with current_in_userns Seth Forshee <seth.forshee@canonical.com> - 2016-04-22 17:50 +0200
  [PATCH v3 06/21] fs: Treat foreign mounts as nosuid Seth Forshee <seth.forshee@canonical.com> - 2016-04-22 18:00 +0200
  [PATCH v3 07/21] selinux: Add support for unprivileged mounts from user namespaces Seth Forshee <seth.forshee@canonical.com> - 2016-04-22 18:00 +0200
  [PATCH v3 03/21] fs: Allow sysfs and cgroupfs to share super blocks between user namespaces Seth Forshee <seth.forshee@canonical.com> - 2016-04-22 18:00 +0200
    Re: [PATCH v3 03/21] fs: Allow sysfs and cgroupfs to share super  blocks between user namespaces "Serge E. Hallyn" <serge@hallyn.com> - 2016-04-25 21:10 +0200
  [PATCH v3 02/21] fs: Remove check of s_user_ns for existing mounts in fs_fully_visible() Seth Forshee <seth.forshee@canonical.com> - 2016-04-22 18:00 +0200

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