linux-kernel - Re: [RFC PATCH 3/7] module: prepare to handle ROX allocations for text

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <ZiDz4YbIHEOAnpwF@kernel.org>
Date: Thu, 18 Apr 2024 13:20:17 +0300
From: Mike Rapoport <rppt@...nel.org>
To: Nadav Amit <nadav.amit@...il.com>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andy Lutomirski <luto@...nel.org>, Arnd Bergmann <arnd@...db.de>,
	Catalin Marinas <catalin.marinas@....com>,
	Christoph Hellwig <hch@...radead.org>, Helge Deller <deller@....de>,
	Lorenzo Stoakes <lstoakes@...il.com>,
	Luis Chamberlain <mcgrof@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Palmer Dabbelt <palmer@...belt.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Russell King <linux@...linux.org.uk>, Song Liu <song@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Uladzislau Rezki <urezki@...il.com>, Will Deacon <will@...nel.org>,
	bpf@...r.kernel.org, linux-arch@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	"open list:MEMORY MANAGEMENT" <linux-mm@...ck.org>,
	linux-modules@...r.kernel.org, linux-parisc@...r.kernel.org,
	linux-riscv@...ts.infradead.org, linux-trace-kernel@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org,
	the arch/x86 maintainers <x86@...nel.org>
Subject: Re: [RFC PATCH 3/7] module: prepare to handle ROX allocations for
 text

On Tue, Apr 16, 2024 at 12:36:08PM +0300, Nadav Amit wrote:
> 
> 
> > On 11 Apr 2024, at 19:05, Mike Rapoport <rppt@...nel.org> wrote:
> > 
> > @@ -2440,7 +2479,24 @@ static int post_relocation(struct module *mod, const struct load_info *info)
> > 	add_kallsyms(mod, info);
> > 
> > 	/* Arch-specific module finalizing. */
> > -	return module_finalize(info->hdr, info->sechdrs, mod);
> > +	ret = module_finalize(info->hdr, info->sechdrs, mod);
> > +	if (ret)
> > +		return ret;
> > +
> > +	for_each_mod_mem_type(type) {
> > +		struct module_memory *mem = &mod->mem[type];
> > +
> > +		if (mem->is_rox) {
> > +			if (!execmem_update_copy(mem->base, mem->rw_copy,
> > +						 mem->size))
> > +				return -ENOMEM;
> > +
> > +			vfree(mem->rw_copy);
> > +			mem->rw_copy = NULL;
> > +		}
> > +	}
> > +
> > +	return 0;
> > }
> 
> I might be missing something, but it seems a bit racy.
> 
> IIUC, module_finalize() calls alternatives_smp_module_add(). At this
> point, since you don’t hold the text_mutex, some might do text_poke(),
> e.g., by enabling/disabling static-key, and the update would be
> overwritten. No?

Right :(
Even worse, for UP case alternatives_smp_unlock() will "patch" still empty
area.

So I'm thinking about calling alternatives_smp_module_add() from an
additional callback after the execmem_update_copy().

Does it make sense to you?

-- 
Sincerely yours,
Mike.