From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-870783-1520357657-2-5683600582289824315 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no X-Spam-score: 0.0 X-Spam-hits: BAYES_00 -1.9, RCVD_IN_DNSWL_HI -5, T_RP_MATCHES_RCVD -0.01, LANGUAGES en, BAYES_USED global, SA_VERSION 3.4.0 X-Spam-source: IP='209.132.180.67', Host='vger.kernel.org', Country='CN', FromHeader='org', MailFrom='org' X-Spam-charsets: X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: stable-owner@vger.kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=arctest; t=1520357656; b=MFNB0ifjHuIFm+czrIfE7QJ1T7QVSaYOFsO6lwF6kfM3wqF 2bglaPOO5gLPHS4osCfIGP01TL5u+fLiUzLjgANk0xwJFTw95jAjJzMCQXAI1nXd e5pPqUlJVld69w901ev8W7WKOBewFDk2CEmOssC8gW/IcGldM3/htliAfb2yBBl2 iw/AEGDZasABLTH695abXqmTfLQd/9IN3R/uIAC/pmTbCEG9t5SBV2sNTRhLWuiy eRR9Y4aPsiFVXKPWA9YzbUGkRL88ZL42pUpFglRmzKS8z1mCnW70eCNwPRicX1q0 gAWkP9A5iyLP8xOY72oR6FZ0viapsOiRjrWIUlA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=from:to:cc:subject:date:message-id :in-reply-to:references:sender:list-id; s=arctest; t=1520357656; bh=GLWObaPTIUZ6EtonGulkOVQ0MK3T4Q3B2oWXZVMUsTo=; b=demKQFL8NhUS VBpauQ6+pfapWzde5Xfy2j/KLNusJ9eO7cFbo1h/bIt/BmcRDyRYlk6AJJhugUjh Oln0wHCokyaEkRMPWyPcPjvj2yxEPOmKTich6fbkuFy2fLzNc/bec2pOreHTcKjH jW/pvtTJ+x6Y3wICa4NyEaitlJmJ/ZvyzSpnnAJqvRFM8YOf34R6MXTS0JdaHdyg tcLUOoWt7ugPAkb6hkKwDxiR6KFushjP+TUB38mRgBbjPDORl4d7zA4r/tKE6BRE ADpYsXYORsKGI5GX/o2r+JudBRn7sLXpgV0/SqaIRA8E5TGaxaJLsZuv1U9sGOap jPspy4mHsQ== ARC-Authentication-Results: i=1; mx3.messagingengine.com; arc=none (no signatures found); dkim=fail (message has been altered; 2048-bit rsa key sha256) header.d=gmail.com header.i=@gmail.com header.b=cxRejNdU x-bits=2048 x-keytype=rsa x-algorithm=sha256 x-selector=20161025; dmarc=none (p=none,has-list-id=yes,d=none) header.from=kernel.org; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=orgdomain_pass; x-category=clean score=0 state=0; x-google-dkim=fail (message has been altered; 2048-bit rsa key) header.d=1e100.net header.i=@1e100.net header.b=NfEDQP31; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=kernel.org header.result=pass header_is_org_domain=yes Authentication-Results: mx3.messagingengine.com; arc=none (no signatures found); dkim=fail (message has been altered; 2048-bit rsa key sha256) header.d=gmail.com header.i=@gmail.com header.b=cxRejNdU x-bits=2048 x-keytype=rsa x-algorithm=sha256 x-selector=20161025; dmarc=none (p=none,has-list-id=yes,d=none) header.from=kernel.org; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=orgdomain_pass; x-category=clean score=0 state=0; x-google-dkim=fail (message has been altered; 2048-bit rsa key) header.d=1e100.net header.i=@1e100.net header.b=NfEDQP31; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=kernel.org header.result=pass header_is_org_domain=yes Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932078AbeCFReP (ORCPT ); Tue, 6 Mar 2018 12:34:15 -0500 Received: from mail-yw0-f195.google.com ([209.85.161.195]:35384 "EHLO mail-yw0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753890AbeCFReN (ORCPT ); Tue, 6 Mar 2018 12:34:13 -0500 X-Google-Smtp-Source: AG47ELv1noWe+cN1QwTveYes85hfNJzvBhSLKDkb0UkzagQHx1BtmMVHZkKlbBP3wMa4z+OmsqrdXA== From: Tejun Heo To: torvalds@linux-foundation.org, jannh@google.com, paulmck@linux.vnet.ibm.com, bcrl@kvack.org, viro@zeniv.linux.org.uk, kent.overstreet@gmail.com Cc: security@kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, Tejun Heo , stable@vger.kernel.org Subject: [PATCH 2/7] fs/aio: Use RCU accessors for kioctx_table->table[] Date: Tue, 6 Mar 2018 09:33:11 -0800 Message-Id: <20180306173316.3088458-2-tj@kernel.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20180306173316.3088458-1-tj@kernel.org> References: <20180306172657.3060270-1-tj@kernel.org> <20180306173316.3088458-1-tj@kernel.org> Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: While converting ioctx index from a list to a table, db446a08c23d ("aio: convert the ioctx list to table lookup v3") missed tagging kioctx_table->table[] as an array of RCU pointers and using the appropriate RCU accessors. This introduces a small window in the lookup path where init and access may race. Mark kioctx_table->table[] with __rcu and use the approriate RCU accessors when using the field. Signed-off-by: Tejun Heo Reported-by: Jann Horn Fixes: db446a08c23d ("aio: convert the ioctx list to table lookup v3") Cc: Benjamin LaHaise Cc: Linus Torvalds Cc: stable@vger.kernel.org --- fs/aio.c | 21 +++++++++++---------- 1 file changed, 11 insertions(+), 10 deletions(-) diff --git a/fs/aio.c b/fs/aio.c index eb2e0cf..6bcd3fb 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -68,9 +68,9 @@ struct aio_ring { #define AIO_RING_PAGES 8 struct kioctx_table { - struct rcu_head rcu; - unsigned nr; - struct kioctx *table[]; + struct rcu_head rcu; + unsigned nr; + struct kioctx __rcu *table[]; }; struct kioctx_cpu { @@ -330,7 +330,7 @@ static int aio_ring_mremap(struct vm_area_struct *vma) for (i = 0; i < table->nr; i++) { struct kioctx *ctx; - ctx = table->table[i]; + ctx = rcu_dereference(table->table[i]); if (ctx && ctx->aio_ring_file == file) { if (!atomic_read(&ctx->dead)) { ctx->user_id = ctx->mmap_base = vma->vm_start; @@ -666,9 +666,9 @@ static int ioctx_add_table(struct kioctx *ctx, struct mm_struct *mm) while (1) { if (table) for (i = 0; i < table->nr; i++) - if (!table->table[i]) { + if (!rcu_access_pointer(table->table[i])) { ctx->id = i; - table->table[i] = ctx; + rcu_assign_pointer(table->table[i], ctx); spin_unlock(&mm->ioctx_lock); /* While kioctx setup is in progress, @@ -849,8 +849,8 @@ static int kill_ioctx(struct mm_struct *mm, struct kioctx *ctx, } table = rcu_dereference_raw(mm->ioctx_table); - WARN_ON(ctx != table->table[ctx->id]); - table->table[ctx->id] = NULL; + WARN_ON(ctx != rcu_access_pointer(table->table[ctx->id])); + RCU_INIT_POINTER(table->table[ctx->id], NULL); spin_unlock(&mm->ioctx_lock); /* free_ioctx_reqs() will do the necessary RCU synchronization */ @@ -895,7 +895,8 @@ void exit_aio(struct mm_struct *mm) skipped = 0; for (i = 0; i < table->nr; ++i) { - struct kioctx *ctx = table->table[i]; + struct kioctx *ctx = + rcu_dereference_protected(table->table[i], true); if (!ctx) { skipped++; @@ -1084,7 +1085,7 @@ static struct kioctx *lookup_ioctx(unsigned long ctx_id) if (!table || id >= table->nr) goto out; - ctx = table->table[id]; + ctx = rcu_dereference(table->table[id]); if (ctx && ctx->user_id == ctx_id) { percpu_ref_get(&ctx->users); ret = ctx; -- 2.9.5