Re: [PATCH v1 0/1] Unprivileged chroot

On 3/10/2021 8:09 AM, Mickaël Salaün wrote:

Hi,

The chroot system call is currently limited to be used by processes with
the CAP_SYS_CHROOT capability.  This protects against malicious
procesess willing to trick SUID-like binaries.  The following patch
allows unprivileged users to safely use chroot(2).

Mount namespaces have pretty well obsoleted chroot(). CAP_SYS_CHROOT is
one of the few fine grained capabilities. We're still finding edge cases
(e.g. ptrace) where no_new_privs is imperfect. I doesn't seem that there
is a compelling reason to remove the privilege requirement on chroot().

This patch is a follow-up of a previous one sent by Andy Lutomirski some
time ago:
https://lore.kernel.org/lkml/0e2f0f54e19bff53a3739ecfddb4ffa9a6dbde4d.1327858005.git.luto@amacapital.net/ (local)

This patch can be applied on top of v5.12-rc2 .  I would really
appreciate constructive reviews.

Regards,

Mickaël Salaün (1):
  fs: Allow no_new_privs tasks to call chroot(2)

 fs/open.c | 64 ++++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 61 insertions(+), 3 deletions(-)


base-commit: a38fd8748464831584a19438cbb3082b5a2dab15