From patchwork Thu Mar 18 10:08:25 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vijayanand Jitta X-Patchwork-Id: 12147787 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7A829C433E0 for ; Thu, 18 Mar 2021 10:09:06 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id D69FD64E86 for ; Thu, 18 Mar 2021 10:09:05 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D69FD64E86 Authentication-Results: mail.kernel.org; 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Thu, 18 Mar 2021 10:08:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 996FCC433CA Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; spf=fail smtp.mailfrom=vjitta@codeaurora.org From: vjitta@codeaurora.org To: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: vjitta@codeaurora.org, vinmenon@codeaurora.org Subject: [PATCH] mm: vmalloc: Prevent use after free in _vm_unmap_aliases Date: Thu, 18 Mar 2021 15:38:25 +0530 Message-Id: <1616062105-23263-1-git-send-email-vjitta@codeaurora.org> X-Mailer: git-send-email 2.7.4 X-Stat-Signature: h74g5h5u4zut3bepusougnredda18iaw X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: DC8946000104 Received-SPF: none (mg.codeaurora.org>: No applicable sender policy available) receiver=imf09; identity=mailfrom; envelope-from=""; helo=m42-10.mailgun.net; client-ip=69.72.42.10 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1616062141-921233 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: From: Vijayanand Jitta A potential use after free can occur in _vm_unmap_aliases where an already freed vmap_area could be accessed, Consider the following scenario: Process 1 Process 2 __vm_unmap_aliases __vm_unmap_aliases purge_fragmented_blocks_allcpus rcu_read_lock() rcu_read_lock() list_del_rcu(&vb->free_list) list_for_each_entry_rcu(vb .. ) __purge_vmap_area_lazy kmem_cache_free(va) va_start = vb->va->va_start Here Process 1 is in purge path and it does list_del_rcu on vmap_block and later frees the vmap_area, since Process 2 was holding the rcu lock at this time vmap_block will still be present in and Process 2 accesse it and thereby it tries to access vmap_area of that vmap_block which was already freed by Process 1 and this results in use after free. Fix this by adding a check for vb->dirty before accessing vmap_area structure since vb->dirty will be set to VMAP_BBMAP_BITS in purge path checking for this will prevent the use after free. Signed-off-by: Vijayanand Jitta Reviewed-by: Uladzislau Rezki (Sony) --- mm/vmalloc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index d5f2a84..ebb6f57 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -1762,7 +1762,7 @@ static void _vm_unmap_aliases(unsigned long start, unsigned long end, int flush) rcu_read_lock(); list_for_each_entry_rcu(vb, &vbq->free, free_list) { spin_lock(&vb->lock); - if (vb->dirty) { + if (vb->dirty && vb->dirty != VMAP_BBMAP_BITS) { unsigned long va_start = vb->va->va_start; unsigned long s, e;