From: Miklos Szeredi 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 Cc: Ram Pai Cc: Christoph Hellwig Signed-off-by: Andrew Morton --- fs/namespace.c | 23 ++++++++++++++++++++++- 1 file changed, 22 insertions(+), 1 deletion(-) diff -puN fs/namespace.c~unprivileged-mounts-allow-unprivileged-umount fs/namespace.c --- a/fs/namespace.c~unprivileged-mounts-allow-unprivileged-umount +++ a/fs/namespace.c @@ -639,6 +639,27 @@ 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. @@ -662,7 +683,7 @@ asmlinkage long sys_umount(char __user * goto dput_and_out; retval = -EPERM; - if (!capable(CAP_SYS_ADMIN)) + if (!permit_umount(nd.mnt, flags)) goto dput_and_out; retval = do_umount(nd.mnt, flags); _