bug#47324: AW: bug#47324: Missing information in documentation

[Bernhard Voelker]

On 3/23/21 11:18 AM, Walter Harms via GNU coreutils Bug Reports wrote:
> In my case there was no security context involved.
> It was a loop device mounted (that i was not aware of,
> the image was already gone).
> and rm -r stoped here because of "in use".
> 
> I expected some mentioning of mount somewhere.

According to the source code [1], the directory must have had a security
context set.

[1] https://git.sv.gnu.org/cgit/coreutils.git/tree/src/ls.c?id=4698e284f#n4243

So if it was a mount point, then the only logical conclusion is that the 
top-most
directory of the mounted filesystem had this security context set.
Reproducer:

  # Create an EXT4 file system and loop-mount it.
  $ dd if=/dev/zero of=x.img bs=1M count=128 status=none
  $ mkfs.ext4 -q x.img
  $ mount -o loop x.img /mnt

  # Initially, there's no security context, hence no '.' after the permission 
string.
  $ ls -ld /mnt
  drwxr-xr-x 3 root root 1024 Mar 25 23:54 /mnt

  # Apply a security context.
  $ setfattr -n security.selinux -v somevalue /mnt

  # Now, ls(1) prints the '.' after the permission string as a hint to the 
security context.
  $ ls -ld /mnt
  drwxr-xr-x. 3 root root 1024 Mar 25 23:54 /mnt

Have a nice day,
Berny