• Eric W. Biederman's avatar
    vfs: In d_path don't call d_dname on a mount point · f48cfddc
    Eric W. Biederman authored
    Aditya Kali (adityakali@google.com) wrote:
    > Commit bf056bfa:
    > "proc: Fix the namespace inode permission checks." converted
    > the namespace files into symlinks. The same commit changed
    > the way namespace bind mounts appear in /proc/mounts:
    >   $ mount --bind /proc/self/ns/ipc /mnt/ipc
    > Originally:
    >   $ cat /proc/mounts | grep ipc
    >   proc /mnt/ipc proc rw,nosuid,nodev,noexec 0 0
    >
    > After commit bf056bfa:
    >   $ cat /proc/mounts | grep ipc
    >   proc ipc:[4026531839] proc rw,nosuid,nodev,noexec 0 0
    >
    > This breaks userspace which expects the 2nd field in
    > /proc/mounts to be a valid path.
    
    The symlink /proc/<pid>/ns/{ipc,mnt,net,pid,user,uts} point to
    dentries allocated with d_alloc_pseudo that we can mount, and
    that have interesting names printed out with d_dname.
    
    When these files are bind mounted /proc/mounts is not currently
    displaying the mount point correctly because d_dname is called instead
    of just displaying the path where the file is mounted.
    
    Solve this by adding an explicit check to distinguish mounted pseudo
    inodes and unmounted pseudo inodes.  Unmounted pseudo inodes always
    use mount of their filesstem as the mnt_root  in their path making
    these two cases easy to distinguish.
    
    CC: stable@vger.kernel.org
    Acked-by: default avatarSerge Hallyn <serge.hallyn@canonical.com>
    Reported-by: default avatarAditya Kali <adityakali@google.com>
    Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
    f48cfddc
dcache.c 87.7 KB