Messages in this thread Patch in this message | | | Date | Tue, 05 Feb 2008 22:36:18 +0100 | From | Miklos Szeredi <> | Subject | [patch 02/10] unprivileged mounts: allow unprivileged umount |
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From: Miklos Szeredi <mszeredi@suse.cz>
The owner doesn't need sysadmin capabilities to call umount().
Similar behavior as umount(8) on mounts having "user=UID" option in /etc/mtab. The difference is that umount also checks /etc/fstab, presumably to exclude another mount on the same mountpoint.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Acked-by: Serge Hallyn <serue@us.ibm.com> ---
Index: linux/fs/namespace.c =================================================================== --- linux.orig/fs/namespace.c 2008-02-04 23:47:50.000000000 +0100 +++ linux/fs/namespace.c 2008-02-04 23:47:53.000000000 +0100 @@ -1033,6 +1033,27 @@ static int do_umount(struct vfsmount *mn return retval; } +static bool is_mount_owner(struct vfsmount *mnt, uid_t uid) +{ + return (mnt->mnt_flags & MNT_USER) && mnt->mnt_uid == uid; +} + +/* + * umount is permitted for + * - sysadmin + * - mount owner, if not forced umount + */ +static bool permit_umount(struct vfsmount *mnt, int flags) +{ + if (capable(CAP_SYS_ADMIN)) + return true; + + if (flags & MNT_FORCE) + return false; + + return is_mount_owner(mnt, current->fsuid); +} + /* * Now umount can handle mount points as well as block devices. * This is important for filesystems which use unnamed block devices. @@ -1056,7 +1077,7 @@ asmlinkage long sys_umount(char __user * goto dput_and_out; retval = -EPERM; - if (!capable(CAP_SYS_ADMIN)) + if (!permit_umount(nd.path.mnt, flags)) goto dput_and_out; retval = do_umount(nd.path.mnt, flags); --
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