From patchwork Wed Jun 19 19:33:54 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kees Cook X-Patchwork-Id: 13704470 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 858C015921D; Wed, 19 Jun 2024 19:33:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718825638; cv=none; b=k57D+O9B8kun7RBMxFIBOWM00CsT837xceeZ3ALtWULwCeXF55OQWFYZ0lbIFadcHzGNuPTj2h9lOBYy6Hmux4WYPBe2ooKrm9wdLZn1Br4Ai85X27QTROuEnN78DCs+rfFnwjmYzTim9jsnMQUqy1rl1OPshs015c1t75e6M/o= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718825638; c=relaxed/simple; bh=LrnolFNHWclGZ9p3hY/QGRuJsr6+6G+8GF/8xJCY8DU=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=sYG+zqaNvNblG7g8GGyaUT99qmzktI1gyGulXz17l8oSZ8oe3QW6i37E0F6zUz9XFwgfhwfkqdhBWhxVmzN8JVFP4Fx+r/scDYvHlA9kH+lyNtDg0nM8NsySbZm/GTEAec5x5ECqKmOOJpF9nmOxxxQ/d8YX1qjKKiwe/JR/D+Y= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Pc6m2Jyd; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Pc6m2Jyd" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2C6FAC4AF0A; Wed, 19 Jun 2024 19:33:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1718825638; bh=LrnolFNHWclGZ9p3hY/QGRuJsr6+6G+8GF/8xJCY8DU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Pc6m2JydDigHX1wPdvV7BSO6pjR4OiuefHdkKa1fdpttENlQLKGuUfbGFFSu2l4Lm lQD5iAks3gvBoAIfaXZXsbn9df6WJYs3vBKiEbv3bJ4PaaLahoIa4QSNZ1SYfuLbBH EC/g9SUx1BXID0KIUyOFIJTu1RoIyozImXz+TkjeVy0SusKmCLRASggim94z6rYRCM tO4C6jMpK8ZWUlJKguJ9sfCfZZJc1MVWVRiBXSV+GO5TXMdXWOzrdcFw/b8i8cgg7U lBK0Q0+bcSuO5G7slNZJMYU9DBvzN/fxnRHAqOvcn3r1IAoqVZP9OzadrVNBk/NTEU Fodm/pnVMavLA== From: Kees Cook To: Vlastimil Babka Cc: Kees Cook , "GONG, Ruiqi" , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , jvoisin , Andrew Morton , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Xiu Jianfeng , Suren Baghdasaryan , Kent Overstreet , Jann Horn , Matteo Rizzo , Thomas Graf , Herbert Xu , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-hardening@vger.kernel.org, netdev@vger.kernel.org Subject: [PATCH v5 6/6] mm/util: Use dedicated slab buckets for memdup_user() Date: Wed, 19 Jun 2024 12:33:54 -0700 Message-Id: <20240619193357.1333772-6-kees@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240619192131.do.115-kees@kernel.org> References: <20240619192131.do.115-kees@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2799; i=kees@kernel.org; h=from:subject; bh=LrnolFNHWclGZ9p3hY/QGRuJsr6+6G+8GF/8xJCY8DU=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBmczKhEAWYa/Ji7QXOW1GAYZ9rnB+j1DB6dbkqF TcWKMWXK8GJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCZnMyoQAKCRCJcvTf3G3A Jna9D/9jn8FgmhtJGIsF1k6FXqxnOb5H/Edjil/UGnza0ThNC5KYFYysA7NmGEt75u5Ul8yTo/m mPSLD5BsKR+jO9ra+Jb1otzerSK7RPkiM6Imdxr4fUVqJRDIyZfow5kmiqU9kP3XohZkW6L9tCf Gg3Gf3IyVqjtN6r7kMQfjfEwb0asp7l19n+RBG+Y+rCjuwW9f0zVuora95LsN+puXykCTSHPd8l triyydYzJHXgpSTHex+MpUFovzc22Spf+qmwDTaHqtewlJLtF0Yv2hU8zovuwGlpfr8ByOElpfK Vk+S54XYZnxOLQ67p3popKVW0MElvIx5m8o5iUKZDmwhhLvPBOzUH1bT6we+7qxY02Rjs8l7tcq 2WQdGuzFjXnYo2mAqRN7l7S7Cq1nPwRpwtPoUinjqbvdFIV/NRq9GABynRSpDqxH5qrbas9689/ gvJkHTXbL+PSnY6Qs32jdRqdMuCqHzXkPa02gx1uuVpAPC8z9C0JsTzVOz30ZPQ9b0RmeBt9pE6 lT0nq+2zyjP5Wa+1oEckM/FhVlBq0s4VsGGABVI6DWi7oWRyz/ZZfn5gV0N4qWgfnHJalyM3cFC 3O6fBUVeH3zAlDMwpz+DEypq18nKLYt6AtEq5WMurqTQR+ES3H6DKAtjc5xSYw6hrbgAMWMSOLR smdpkS6OJkKmNzw== X-Developer-Key: i=kees@kernel.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Both memdup_user() and vmemdup_user() handle allocations that are regularly used for exploiting use-after-free type confusion flaws in the kernel (e.g. prctl() PR_SET_VMA_ANON_NAME[1] and setxattr[2][3][4] respectively). Since both are designed for contents coming from userspace, it allows for userspace-controlled allocation sizes. Use a dedicated set of kmalloc buckets so these allocations do not share caches with the global kmalloc buckets. After a fresh boot under Ubuntu 23.10, we can see the caches are already in active use: # grep ^memdup /proc/slabinfo memdup_user-8k 4 4 8192 4 8 : ... memdup_user-4k 8 8 4096 8 8 : ... memdup_user-2k 16 16 2048 16 8 : ... memdup_user-1k 0 0 1024 16 4 : ... memdup_user-512 0 0 512 16 2 : ... memdup_user-256 0 0 256 16 1 : ... memdup_user-128 0 0 128 32 1 : ... memdup_user-64 256 256 64 64 1 : ... memdup_user-32 512 512 32 128 1 : ... memdup_user-16 1024 1024 16 256 1 : ... memdup_user-8 2048 2048 8 512 1 : ... memdup_user-192 0 0 192 21 1 : ... memdup_user-96 168 168 96 42 1 : ... Link: https://starlabs.sg/blog/2023/07-prctl-anon_vma_name-an-amusing-heap-spray/ [1] Link: https://duasynt.com/blog/linux-kernel-heap-spray [2] Link: https://etenal.me/archives/1336 [3] Link: https://github.com/a13xp0p0v/kernel-hack-drill/blob/master/drill_exploit_uaf.c [4] Signed-off-by: Kees Cook --- mm/util.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/mm/util.c b/mm/util.c index 28c5356b9f1c..6f0fcc5f4243 100644 --- a/mm/util.c +++ b/mm/util.c @@ -198,6 +198,16 @@ char *kmemdup_nul(const char *s, size_t len, gfp_t gfp) } EXPORT_SYMBOL(kmemdup_nul); +static kmem_buckets *user_buckets __ro_after_init; + +static int __init init_user_buckets(void) +{ + user_buckets = kmem_buckets_create("memdup_user", 0, 0, 0, INT_MAX, NULL); + + return 0; +} +subsys_initcall(init_user_buckets); + /** * memdup_user - duplicate memory region from user space * @@ -211,7 +221,7 @@ void *memdup_user(const void __user *src, size_t len) { void *p; - p = kmalloc_track_caller(len, GFP_USER | __GFP_NOWARN); + p = kmem_buckets_alloc_track_caller(user_buckets, len, GFP_USER | __GFP_NOWARN); if (!p) return ERR_PTR(-ENOMEM); @@ -237,7 +247,7 @@ void *vmemdup_user(const void __user *src, size_t len) { void *p; - p = kvmalloc(len, GFP_USER); + p = kmem_buckets_valloc(user_buckets, len, GFP_USER); if (!p) return ERR_PTR(-ENOMEM);