Re: [PATCH 24/32] vfs: syscall: Add fsopen() to prepare for superblock creation [ver #9]

On Jul 11, 2018, at 12:22 AM, David Howells [off-list ref] wrote:

Andy Lutomirski [off-list ref] wrote:

quoted

quoted

  sfd = fsopen("ext4", FSOPEN_CLOEXEC);
  write(sfd, "s /dev/sdb1"); // note I'm ignoring write's length arg

Imagine some malicious program passes sfd as stdout to a setuid
program. That program gets persuaded to write "s /etc/shadow".  What
happens?  You’re okay as long as *every single fs* gets it right, but that’s
asking a lot.

Do note that you must already have CAP_SYS_ADMIN to be able to call fsopen().

If you’re not allowing it already, someone will want user namespace
root to be able to use this very, very soon.