netdev - Re: [Bugme-new] [Bug 33502] New: Caught 64-bit read from uninitialized memory in __alloc

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: <alpine.DEB.2.00.1105101242420.2875@router.home>
Date:	Tue, 10 May 2011 12:43:28 -0500 (CDT)
From:	Christoph Lameter <cl@...ux.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
cc:	Vegard Nossum <vegardno@....uio.no>,
	Pekka Enberg <penberg@...helsinki.fi>,
	casteyde.christian@...e.fr,
	Andrew Morton <akpm@...ux-foundation.org>,
	netdev@...r.kernel.org, bugzilla-daemon@...zilla.kernel.org,
	bugme-daemon@...zilla.kernel.org
Subject: Re: [Bugme-new] [Bug 33502] New: Caught 64-bit read from uninitialized
 memory in __alloc_skb


Draft for a patch


Subject: slub: Make CONFIG_PAGE_ALLOC work with new fastpath

Fastpath can do a speculative access to a page that CONFIG_PAGE_ALLOC may have
marked as invalid to retrieve the pointer to the next free object.

Probe that address before dereferencing the pointer to the page.
All of that needs to occur with interrupts disabled since an interrupt
could cause the page status to change (as pointed out by Eric).

Signed-off-by: Christoph Lameter <cl@...ux.com>
---
 mm/slub.c |   23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

Index: linux-2.6/mm/slub.c
===================================================================
--- linux-2.6.orig/mm/slub.c	2011-05-10 12:35:30.000000000 -0500
+++ linux-2.6/mm/slub.c	2011-05-10 12:38:53.000000000 -0500
@@ -261,6 +261,27 @@ static inline void *get_freepointer(stru
 	return *(void **)(object + s->offset);
 }

+static inline void *get_freepointer_safe(struct kmem_cache *s, void *object)
+{
+	void *p;
+
+#ifdef CONFIG_PAGE_ALLOC
+	unsigned long flags;
+
+	local_irq_save(flags);
+
+	if (probe_kernel_address(object))
+		p = NULL;	/* Invalid */
+	else
+		p = get_freepointer(s, object);
+
+	local_irq_restore(flags);
+#else
+	p = get_freepointer(s, object);
+#endif
+	return p;
+}
+
 static inline void set_freepointer(struct kmem_cache *s, void *object, void *fp)
 {
 	*(void **)(object + s->offset) = fp;
@@ -1933,7 +1954,7 @@ redo:
 		if (unlikely(!irqsafe_cpu_cmpxchg_double(
 				s->cpu_slab->freelist, s->cpu_slab->tid,
 				object, tid,
-				get_freepointer(s, object), next_tid(tid)))) {
+				get_freepointer_safe(s, object), next_tid(tid)))) {

 			note_cmpxchg_failure("slab_alloc", s, tid);
 			goto redo;
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html