linux-kernel - Re: [PATCH v2 4/7] arm64/modules: Add rlimit checking for arm64 modules

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Date:   Fri, 12 Oct 2018 22:54:00 +0000
From:   "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To:     "jeyu@...nel.org" <jeyu@...nel.org>,
        "Hansen, Dave" <dave.hansen@...el.com>
CC:     "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        "keescook@...omium.org" <keescook@...omium.org>,
        "arjan@...ux.intel.com" <arjan@...ux.intel.com>,
        "linux-mips@...ux-mips.org" <linux-mips@...ux-mips.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "linux-s390@...r.kernel.org" <linux-s390@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "kristen@...ux.intel.com" <kristen@...ux.intel.com>,
        "Dock, Deneen T" <deneen.t.dock@...el.com>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
        "mingo@...hat.com" <mingo@...hat.com>,
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        "kernel-hardening@...ts.openwall.com" 
        <kernel-hardening@...ts.openwall.com>,
        "bp@...en8.de" <bp@...en8.de>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "arnd@...db.de" <arnd@...db.de>,
        "sparclinux@...r.kernel.org" <sparclinux@...r.kernel.org>
Subject: Re: [PATCH v2 4/7] arm64/modules: Add rlimit checking for arm64
 modules

On Fri, 2018-10-12 at 22:01 +0000, Edgecombe, Rick P wrote:
> On Fri, 2018-10-12 at 16:32 +0200, Jessica Yu wrote:
> > +++ Dave Hansen [11/10/18 16:47 -0700]:
> > > On 10/11/2018 04:31 PM, Rick Edgecombe wrote:
> > > > +	if (check_inc_mod_rlimit(size))
> > > > +		return NULL;
> > > > +
> > > >  	p = __vmalloc_node_range(size, MODULE_ALIGN, module_alloc_base,
> > > >  				module_alloc_base + MODULES_VSIZE,
> > > >  				gfp_mask, PAGE_KERNEL_EXEC, 0,
> > > > @@ -65,6 +68,8 @@ void *module_alloc(unsigned long size)
> > > >  		return NULL;
> > > >  	}
> > > > 
> > > > +	update_mod_rlimit(p, size);
> > > 
> > > Is there a reason we couldn't just rename all of the existing per-arch
> > > module_alloc() calls to be called, say, "arch_module_alloc()", then put
> > > this new rlimit code in a generic helper that does:
> > > 
> > > 
> > > 	if (check_inc_mod_rlimit(size))
> > > 		return NULL;
> > > 
> > > 	p = arch_module_alloc(...);
> > > 
> > > 	...
> > > 
> > > 	update_mod_rlimit(p, size);
> > > 
> > 
> > I second this suggestion. Just make module_{alloc,memfree} generic,
> > non-weak functions that call the rlimit helpers in addition to the
> > arch-specific arch_module_{alloc,memfree} functions.
> > 
> > Jessica
> 
> Ok, thanks. I am going to try another version of this with just a system wide
> BPF JIT limit based on the problems Jann brought up. I think it would be nice
> to
> have a module space limit, but as far as I know the only way today un-
> privlidged 
> users could fill the space is from BPF JIT. Unless you see another purpose
> long
> term?

Err, nevermind. Going to try to include both limits. I'll incorporate this
refactor into the next version.