[PATCH] security: new security_file_ioctl_compat() hook

[Eric Biggers]

On Sun, Dec 24, 2023 at 03:53:16PM -0500, Paul Moore wrote:
> On Tue, Dec 19, 2023 at 4:09 AM Alfred Piccioni <alpic at google.com> wrote:
> >
> > Some ioctl commands do not require ioctl permission, but are routed to
> > other permissions such as FILE_GETATTR or FILE_SETATTR. This routing is
> > done by comparing the ioctl cmd to a set of 64-bit flags (FS_IOC_*).
> >
> > However, if a 32-bit process is running on a 64-bit kernel, it emits
> > 32-bit flags (FS_IOC32_*) for certain ioctl operations. These flags are
> > being checked erroneously, which leads to these ioctl operations being
> > routed to the ioctl permission, rather than the correct file
> > permissions.
> >
> > This was also noted in a RED-PEN finding from a while back -
> > "/* RED-PEN how should LSM module know it's handling 32bit? */".
> >
> > This patch introduces a new hook, security_file_ioctl_compat, that is
> > called from the compat ioctl syscall. All current LSMs have been changed
> > to support this hook.
> >
> > Reviewing the three places where we are currently using
> > security_file_ioctl, it appears that only SELinux needs a dedicated
> > compat change; TOMOYO and SMACK appear to be functional without any
> > change.
> >
> > Fixes: 0b24dcb7f2f7 ("Revert "selinux: simplify ioctl checking"")
> > Signed-off-by: Alfred Piccioni <alpic at google.com>
> > Cc: stable at vger.kernel.org
> > ---
> >  fs/ioctl.c                    |  3 +--
> >  include/linux/lsm_hook_defs.h |  2 ++
> >  include/linux/security.h      |  7 +++++++
> >  security/security.c           | 17 +++++++++++++++++
> >  security/selinux/hooks.c      | 28 ++++++++++++++++++++++++++++
> >  security/smack/smack_lsm.c    |  1 +
> >  security/tomoyo/tomoyo.c      |  1 +
> >  7 files changed, 57 insertions(+), 2 deletions(-)
> 
> I made some minor style tweaks around line length and alignment, but
> otherwise this looked good to me.  Thanks all!
> 

Reviewed-by: Eric Biggers <ebiggers at google.com>

(I reviewed the version in branch "next" of
https://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/lsm.git)

- Eric