linux-hardening - [PATCH v5 5/6] ipc, msg: Use dedicated slab buckets for alloc

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Message-Id: <20240619193357.1333772-5-kees@kernel.org>
Date: Wed, 19 Jun 2024 12:33:53 -0700
From: Kees Cook <kees@...nel.org>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: Kees Cook <kees@...nel.org>,
	"GONG, Ruiqi" <gongruiqi@...weicloud.com>,
	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	jvoisin <julien.voisin@...tri.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Roman Gushchin <roman.gushchin@...ux.dev>,
	Hyeonggon Yoo <42.hyeyoo@...il.com>,
	Xiu Jianfeng <xiujianfeng@...wei.com>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Kent Overstreet <kent.overstreet@...ux.dev>,
	Jann Horn <jannh@...gle.com>,
	Matteo Rizzo <matteorizzo@...gle.com>,
	Thomas Graf <tgraf@...g.ch>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	linux-hardening@...r.kernel.org,
	netdev@...r.kernel.org
Subject: [PATCH v5 5/6] ipc, msg: Use dedicated slab buckets for alloc_msg()

The msg subsystem is a common target for exploiting[1][2][3][4][5][6][7]
use-after-free type confusion flaws in the kernel for both read and write
primitives. Avoid having a user-controlled dynamically-size allocation
share the global kmalloc cache by using a separate set of kmalloc buckets
via the kmem_buckets API.

Link: https://blog.hacktivesecurity.com/index.php/2022/06/13/linux-kernel-exploit-development-1day-case-study/ [1]
Link: https://hardenedvault.net/blog/2022-11-13-msg_msg-recon-mitigation-ved/ [2]
Link: https://www.willsroot.io/2021/08/corctf-2021-fire-of-salvation-writeup.html [3]
Link: https://a13xp0p0v.github.io/2021/02/09/CVE-2021-26708.html [4]
Link: https://google.github.io/security-research/pocs/linux/cve-2021-22555/writeup.html [5]
Link: https://zplin.me/papers/ELOISE.pdf [6]
Link: https://syst3mfailure.io/wall-of-perdition/ [7]
Signed-off-by: Kees Cook <kees@...nel.org>
---
 ipc/msgutil.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/ipc/msgutil.c b/ipc/msgutil.c
index d0a0e877cadd..f392f30a057a 100644
--- a/ipc/msgutil.c
+++ b/ipc/msgutil.c
@@ -42,6 +42,17 @@ struct msg_msgseg {
 #define DATALEN_MSG	((size_t)PAGE_SIZE-sizeof(struct msg_msg))
 #define DATALEN_SEG	((size_t)PAGE_SIZE-sizeof(struct msg_msgseg))
 
+static kmem_buckets *msg_buckets __ro_after_init;
+
+static int __init init_msg_buckets(void)
+{
+	msg_buckets = kmem_buckets_create("msg_msg", 0, SLAB_ACCOUNT,
+					  sizeof(struct msg_msg),
+					  DATALEN_MSG, NULL);
+
+	return 0;
+}
+subsys_initcall(init_msg_buckets);
 
 static struct msg_msg *alloc_msg(size_t len)
 {
@@ -50,7 +61,7 @@ static struct msg_msg *alloc_msg(size_t len)
 	size_t alen;
 
 	alen = min(len, DATALEN_MSG);
-	msg = kmalloc(sizeof(*msg) + alen, GFP_KERNEL_ACCOUNT);
+	msg = kmem_buckets_alloc(msg_buckets, sizeof(*msg) + alen, GFP_KERNEL);
 	if (msg == NULL)
 		return NULL;
 
-- 
2.34.1