linux-kernel - Re: [PATCH v15 05/11] LSM: Create lsm_list

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Date: Tue, 12 Mar 2024 13:06:36 -0400
From: Paul Moore <paul@...l-moore.com>
To: Casey Schaufler <casey@...aufler-ca.com>
Cc: "Dmitry V. Levin" <ldv@...ace.io>, linux-security-module@...r.kernel.org, jmorris@...ei.org, 
	serge@...lyn.com, keescook@...omium.org, john.johansen@...onical.com, 
	penguin-kernel@...ove.sakura.ne.jp, stephen.smalley.work@...il.com, 
	linux-kernel@...r.kernel.org, linux-api@...r.kernel.org, mic@...ikod.net
Subject: Re: [PATCH v15 05/11] LSM: Create lsm_list_modules system call

On Tue, Mar 12, 2024 at 11:27 AM Casey Schaufler <casey@...aufler-ca.com> wrote:
> On 3/12/2024 6:25 AM, Paul Moore wrote:
> > On Tue, Mar 12, 2024 at 6:16 AM Dmitry V. Levin <ldv@...ace.io> wrote:
> >> On Tue, Sep 12, 2023 at 01:56:50PM -0700, Casey Schaufler wrote:
> >> [...]
> >>> --- a/security/lsm_syscalls.c
> >>> +++ b/security/lsm_syscalls.c
> >>> @@ -55,3 +55,42 @@ SYSCALL_DEFINE4(lsm_get_self_attr, unsigned int, attr, struct lsm_ctx __user *,
> >>>  {
> >>>       return security_getselfattr(attr, ctx, size, flags);
> >>>  }
> >>> +
> >>> +/**
> >>> + * sys_lsm_list_modules - Return a list of the active security modules
> >>> + * @ids: the LSM module ids
> >>> + * @size: pointer to size of @ids, updated on return
> >>> + * @flags: reserved for future use, must be zero
> >>> + *
> >>> + * Returns a list of the active LSM ids. On success this function
> >>> + * returns the number of @ids array elements. This value may be zero
> >>> + * if there are no LSMs active. If @size is insufficient to contain
> >>> + * the return data -E2BIG is returned and @size is set to the minimum
> >>> + * required size. In all other cases a negative value indicating the
> >>> + * error is returned.
> >>> + */
> >>> +SYSCALL_DEFINE3(lsm_list_modules, u64 __user *, ids, size_t __user *, size,
> >>> +             u32, flags)
> >> I'm sorry but the size of userspace size_t is different from the kernel one
> >> on 32-bit compat architectures.
> > D'oh, yes, thanks for pointing that out.  It would have been nice to
> > have caught that before v6.8 was released, but I guess it's better
> > than later.
> >
> >> Looks like there has to be a COMPAT_SYSCALL_DEFINE3(lsm_list_modules, ..)
> >> now.  Other two added lsm syscalls also have this issue.
> > Considering that Linux v6.8, and by extension these syscalls, are only
> > a few days old, I think I'd rather see us just modify the syscalls and
> > avoid the compat baggage.  I'm going to be shocked if anyone has
> > shifted to using the new syscalls yet, and even if they have (!!),
> > moving from a "size_t" type to a "u64" should be mostly transparent
> > for the majority of native 64-bit systems.  Those running the absolute
> > latest kernels on 32-bit systems with custom or bleeding edge
> > userspace *may* see a slight hiccup, but I think that user count is in
> > the single digits, if not zero.
> >
> > Let's fix this quickly with /size_t/u64/ in v6.8.1 and avoid the
> > compat shim if we can.
> >
> > Casey, do you have time to put together a patch for this (you should
> > fix the call chains below the syscalls too)?  If not, please let me
> > know and I'll get a patch out ASAP.
>
> Grumble. Yes, I'll get right on it.

Great, thanks Casey.

-- 
paul-moore.com