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[209.85.220.65]) by mx.google.com with SMTPS id t9sor493769wrr.16.2019.02.13.16.25.52 for (Google Transport Security); Wed, 13 Feb 2019 16:25:52 -0800 (PST) Received-SPF: pass (google.com: domain of andreyknvl@google.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b=HhlIJr4F; spf=pass (google.com: domain of andreyknvl@google.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=andreyknvl@google.com; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=xv22CgztNiptmL1IpEe32/U9BVLPdU1sqDTM5ZydeiE=; b=HhlIJr4FWxNaNivefuJ+bnt6Cq6HW7Q52ilE48ZsQqjbtnHgee4hlqRgSCcjUyQ3d5 RBdZpO9q2BMCElpsu8MXwIzHOZe5OUT5V8X7obmacrhhCOGKhX8nOQwKazkEjSUND7xk 66AtVE3HBZnXxcev29ErJipHiWd3dzL/rEqAxab/+R7IAKEDZJ8thijXd9ztOjoHl/6C XDXL+vWafOandWWLJMbEb6N1SIHoCLHF4ZsxnBgIJ6z7DVSB23yvsjKxRmeC5yYH+a91 NrmImhn+jkl+ZXn5wJdNRaQrjaLJV9E0JojwqpVn7/1xHsCbw/mYOLRJqUsLR/pLYZu+ /9CA== X-Google-Smtp-Source: AHgI3IYd9U0Z1ZibscRpnAuj8JVl1ut7OMIRHjvQVt/fMZsv+OV+uKxcoCfJmTEmRasdp0dHRvhurg== X-Received: by 2002:adf:9f54:: with SMTP id f20mr542834wrg.88.1550103951643; Wed, 13 Feb 2019 16:25:51 -0800 (PST) Received: from andreyknvl0.muc.corp.google.com ([2a00:79e0:15:13:8ce:d7fa:9f4c:492]) by smtp.gmail.com with ESMTPSA id b3sm1442324wme.27.2019.02.13.16.25.50 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 13 Feb 2019 16:25:50 -0800 (PST) From: Andrey Konovalov To: Andrey Ryabinin , Alexander Potapenko , Dmitry Vyukov , Catalin Marinas , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Qian Cai , Vincenzo Frascino , Kostya Serebryany , Evgeniy Stepanov , Andrey Konovalov Subject: [PATCH] kasan, slub: fix more conflicts with CONFIG_SLAB_FREELIST_HARDENED Date: Thu, 14 Feb 2019 01:25:47 +0100 Message-Id: X-Mailer: git-send-email 2.20.1.791.gb4d0f1c61a-goog MIME-Version: 1.0 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: X-Virus-Scanned: ClamAV using ClamSMTP When CONFIG_KASAN_SW_TAGS is enabled, ptr_addr might be tagged. Normally, this doesn't cause any issues, as both set_freepointer() and get_freepointer() are called with a pointer with the same tag. However, there are some issues with CONFIG_SLUB_DEBUG code. For example, when __free_slub() iterates over objects in a cache, it passes untagged pointers to check_object(). check_object() in turns calls get_freepointer() with an untagged pointer, which causes the freepointer to be restored incorrectly. Add kasan_reset_tag to freelist_ptr(). Also add a detailed comment. Signed-off-by: Andrey Konovalov Reported-by: Qian Cai Tested-by: Qian Cai --- mm/slub.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/mm/slub.c b/mm/slub.c index 80da3a40b74d..c80e6699357c 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -249,7 +249,18 @@ static inline void *freelist_ptr(const struct kmem_cache *s, void *ptr, unsigned long ptr_addr) { #ifdef CONFIG_SLAB_FREELIST_HARDENED - return (void *)((unsigned long)ptr ^ s->random ^ ptr_addr); + /* + * When CONFIG_KASAN_SW_TAGS is enabled, ptr_addr might be tagged. + * Normally, this doesn't cause any issues, as both set_freepointer() + * and get_freepointer() are called with a pointer with the same tag. + * However, there are some issues with CONFIG_SLUB_DEBUG code. For + * example, when __free_slub() iterates over objects in a cache, it + * passes untagged pointers to check_object(). check_object() in turns + * calls get_freepointer() with an untagged pointer, which causes the + * freepointer to be restored incorrectly. + */ + return (void *)((unsigned long)ptr ^ s->random ^ + (unsigned long)kasan_reset_tag((void *)ptr_addr)); #else return ptr; #endif