linux-kernel - Re: [PATCH v2 0/5] mm/slub: Improve data handling of krealloc() when orig

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 for Android: free password hash cracker in your pocket

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

Message-ID: <Zw0UKtx5d2hnHvDV@feng-clx.sh.intel.com>
Date: Mon, 14 Oct 2024 20:52:58 +0800
From: Feng Tang <feng.tang@...el.com>
To: Vlastimil Babka <vbabka@...e.cz>
CC: Marco Elver <elver@...gle.com>, Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Lameter <cl@...ux.com>, Pekka Enberg <penberg@...nel.org>, "David
 Rientjes" <rientjes@...gle.com>, Joonsoo Kim <iamjoonsoo.kim@....com>, "Roman
 Gushchin" <roman.gushchin@...ux.dev>, Hyeonggon Yoo <42.hyeyoo@...il.com>,
	Andrey Konovalov <andreyknvl@...il.com>, Shuah Khan
	<skhan@...uxfoundation.org>, David Gow <davidgow@...gle.com>, "Danilo
 Krummrich" <dakr@...nel.org>, Alexander Potapenko <glider@...gle.com>,
	"Andrey Ryabinin" <ryabinin.a.a@...il.com>, Dmitry Vyukov
	<dvyukov@...gle.com>, Vincenzo Frascino <vincenzo.frascino@....com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>, "kasan-dev@...glegroups.com"
	<kasan-dev@...glegroups.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH v2 0/5] mm/slub: Improve data handling of krealloc() when
 orig_size is enabled

On Mon, Oct 14, 2024 at 10:53:32AM +0200, Vlastimil Babka wrote:
> On 10/14/24 09:52, Feng Tang wrote:
> > On Fri, Oct 04, 2024 at 05:52:10PM +0800, Vlastimil Babka wrote:
> > Thanks for the suggestion!
> > 
> > As there were error report about the NULL slab for big kmalloc object, how
> > about the following code for 
> > 
> > __do_krealloc(const void *p, size_t new_size, gfp_t flags)
> > {
> > 	void *ret;
> > 	size_t ks = 0;
> > 	int orig_size = 0;
> > 	struct kmem_cache *s = NULL;
> > 
> > 	/* Check for double-free. */
> > 	if (likely(!ZERO_OR_NULL_PTR(p))) {
> > 		if (!kasan_check_byte(p))
> > 			return NULL;
> > 
> > 		ks = ksize(p);
> 
> I think this will result in __ksize() doing
>   skip_orig_size_check(folio_slab(folio)->slab_cache, object);
> and we don't want that?

I think that's fine. As later code will re-set the orig_size anyway.
 
> Also the checks below repeat some of the checks of ksize().

Yes, there is some redundancy, mostly the virt_to_slab() 

> So I think in __do_krealloc() we should do things manually to determine ks
> and not call ksize(). Just not break any of the cases ksize() handles
> (kfence, large kmalloc).

OK, originally I tried not to expose internals of __ksize(). Let me
try this way.

Thanks,
Feng

> 
> > 
> > 		/* Some objects have no orig_size, like big kmalloc case */
> > 		if (is_kfence_address(p)) {
> > 			orig_size = kfence_ksize(p);
> > 		} else if (virt_to_slab(p)) {
> > 			s = virt_to_cache(p);
> > 			orig_size = get_orig_size(s, (void *)p);
> > 		}
> > 	} else {
> > 		goto alloc_new;
> > 	}
> > 
> > 	/* If the object doesn't fit, allocate a bigger one */
> > 	if (new_size > ks)
> > 		goto alloc_new;
> > 
> > 	/* Zero out spare memory. */
> > 	if (want_init_on_alloc(flags)) {
> > 		kasan_disable_current();
> > 		if (orig_size && orig_size < new_size)
> > 			memset((void *)p + orig_size, 0, new_size - orig_size);
> > 		else
> > 			memset((void *)p + new_size, 0, ks - new_size);
> > 		kasan_enable_current();
> > 	}
> > 
> > 	/* Setup kmalloc redzone when needed */
> > 	if (s && slub_debug_orig_size(s) && !is_kfence_address(p)) {
> > 		set_orig_size(s, (void *)p, new_size);
> > 		if (s->flags & SLAB_RED_ZONE && new_size < ks)
> > 			memset_no_sanitize_memory((void *)p + new_size,
> > 						SLUB_RED_ACTIVE, ks - new_size);
> > 	}
> > 
> > 	p = kasan_krealloc((void *)p, new_size, flags);
> > 	return (void *)p;
> > 
> > alloc_new:
> > 	ret = kmalloc_node_track_caller_noprof(new_size, flags, NUMA_NO_NODE, _RET_IP_);
> > 	if (ret && p) {
> > 		/* Disable KASAN checks as the object's redzone is accessed. */
> > 		kasan_disable_current();
> > 		memcpy(ret, kasan_reset_tag(p), orig_size ?: ks);
> > 		kasan_enable_current();
> > 	}
> > 
> > 	return ret;
> > }