From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-2426127-1521056732-2-3691715754795513971 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='198.145.29.99', Host='mail.kernel.org', Country='US', FromHeader='org', MailFrom='org' X-Spam-charsets: X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: SRS0=5xW2=GE=gmail.com=htejun@kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=arctest; t=1521056731; b=s0oYpV3rRid6eR3dlYXPTrfY/wqRu59JoD68/ziiNxHzwds IEg9pffBkrNOTcGaoihvjwIGFglA1s1HoLfrZZvbntr8Bp9zf2uF55av1hSSFuE+ RLO463opGtArRzrm6jbQ3Nrufdu3woz3sFC+bvq0ZcD6/F1psOcGct74gBMuGyaL TDRQEwVvqFLBi0N7VV0O1iPek9QAmY75N1Vf5zVp6ce2IJoDG94vGF2eutb6ceHv oOjy5OVBrst7YxNyt+1CoHTrWLxNfIyyrfNePYAobhgl7T1r+OSuDQTZ3dUaug7G Y1gDETbIvoIwy7kMRV3s8mhCAKHu0FjsWBoi0XQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=sender:from:to:cc:subject:date:message-id :in-reply-to:references; s=arctest; t=1521056731; bh=b7S3zDzaG3n vAYmTEo7A2nG7oDmEoR04rXqwN5bqPB8=; b=pKTess9FMY3riGCVc59ppwdq+C3 68jkZtSpUYHkrwe2orvd3/qPxYn4Zl0NofWDiemohzXZ7H9D/wBzN4pdYRYNzcKu XYPetSnCBFui9bV/elinnFuLD1LaB8UVlIOWxo16ElrgDoWuHrhuq4Ug0mClyUDl In0ToSnUjelZdKBR4pZT/mr5zhHNS22/KeoTi7FVEtiSzJNv3BlESLkYGEt5fWJt puelDBS2KZLodlE95gRgSduwcsdZV1Lyob6nZ7O06C2H9s+3RbiK7zR6mvXBVNoJ qQ1H614iYCGK6tZEKNhXssq9PsBtpjfAa9waL6uiu1lcvx//oAgAM1M78DA== ARC-Authentication-Results: i=1; mx6.messagingengine.com; arc=none (no signatures found); dkim=pass (2048-bit rsa key sha256) header.d=gmail.com header.i=@gmail.com header.b=A/7D7D9/ x-bits=2048 x-keytype=rsa x-algorithm=sha256 x-selector=20161025; dmarc=none (p=none,d=none) header.from=kernel.org; iprev=pass policy.iprev=198.145.29.99 (mail.kernel.org); spf=none smtp.mailfrom=SRS0=5xW2=GE=gmail.com=htejun@kernel.org smtp.helo=mail.kernel.org; x-aligned-from=domain_pass; x-category=clean score=0 state=0; x-google-dkim=pass (2048-bit rsa key) header.d=1e100.net header.i=@1e100.net header.b=DfAX3Eby; x-ptr=pass x-ptr-helo=mail.kernel.org x-ptr-lookup=mail.kernel.org; x-return-mx=pass smtp.domain=kernel.org smtp.result=pass smtp_is_org_domain=yes header.domain=kernel.org header.result=pass header_is_org_domain=yes; x-tls=pass version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128 Authentication-Results: mx6.messagingengine.com; arc=none (no signatures found); dkim=pass (2048-bit rsa key sha256) header.d=gmail.com header.i=@gmail.com header.b=A/7D7D9/ x-bits=2048 x-keytype=rsa x-algorithm=sha256 x-selector=20161025; dmarc=none (p=none,d=none) header.from=kernel.org; iprev=pass policy.iprev=198.145.29.99 (mail.kernel.org); spf=none smtp.mailfrom=SRS0=5xW2=GE=gmail.com=htejun@kernel.org smtp.helo=mail.kernel.org; x-aligned-from=domain_pass; x-category=clean score=0 state=0; x-google-dkim=pass (2048-bit rsa key) header.d=1e100.net header.i=@1e100.net header.b=DfAX3Eby; x-ptr=pass x-ptr-helo=mail.kernel.org x-ptr-lookup=mail.kernel.org; x-return-mx=pass smtp.domain=kernel.org smtp.result=pass smtp_is_org_domain=yes header.domain=kernel.org header.result=pass header_is_org_domain=yes; x-tls=pass version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128 X-Remote-Delivered-To: security@kernel.org DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6AAC12077A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=htejun@gmail.com X-Google-Smtp-Source: AG47ELsbdqH4i06i/9+C4NcNMjFCCXDbKzppmi5UTrOlgf3HLovLEBRHoD6ooLylVRdzH5EqtIB75w== Sender: Tejun Heo 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 1/8] fs/aio: Add explicit RCU grace period when freeing kioctx Date: Wed, 14 Mar 2018 12:45:08 -0700 Message-Id: <20180314194515.1661824-1-tj@kernel.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20180314194205.1651587-1-tj@kernel.org> References: <20180314194205.1651587-1-tj@kernel.org> X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: While fixing refcounting, e34ecee2ae79 ("aio: Fix a trinity splat") incorrectly removed explicit RCU grace period before freeing kioctx. The intention seems to be depending on the internal RCU grace periods of percpu_ref; however, percpu_ref uses a different flavor of RCU, sched-RCU. This can lead to kioctx being freed while RCU read protected dereferences are still in progress. Fix it by updating free_ioctx() to go through call_rcu() explicitly. v2: Comment added to explain double bouncing. Signed-off-by: Tejun Heo Reported-by: Jann Horn Fixes: e34ecee2ae79 ("aio: Fix a trinity splat") Cc: Kent Overstreet Cc: Linus Torvalds Cc: stable@vger.kernel.org --- fs/aio.c | 23 +++++++++++++++++++---- 1 file changed, 19 insertions(+), 4 deletions(-) diff --git a/fs/aio.c b/fs/aio.c index a062d75..eb2e0cf 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -115,7 +115,8 @@ struct kioctx { struct page **ring_pages; long nr_pages; - struct work_struct free_work; + struct rcu_head free_rcu; + struct work_struct free_work; /* see free_ioctx() */ /* * signals when all in-flight requests are done @@ -588,6 +589,12 @@ static int kiocb_cancel(struct aio_kiocb *kiocb) return cancel(&kiocb->common); } +/* + * free_ioctx() should be RCU delayed to synchronize against the RCU + * protected lookup_ioctx() and also needs process context to call + * aio_free_ring(), so the double bouncing through kioctx->free_rcu and + * ->free_work. + */ static void free_ioctx(struct work_struct *work) { struct kioctx *ctx = container_of(work, struct kioctx, free_work); @@ -601,6 +608,14 @@ static void free_ioctx(struct work_struct *work) kmem_cache_free(kioctx_cachep, ctx); } +static void free_ioctx_rcufn(struct rcu_head *head) +{ + struct kioctx *ctx = container_of(head, struct kioctx, free_rcu); + + INIT_WORK(&ctx->free_work, free_ioctx); + schedule_work(&ctx->free_work); +} + static void free_ioctx_reqs(struct percpu_ref *ref) { struct kioctx *ctx = container_of(ref, struct kioctx, reqs); @@ -609,8 +624,8 @@ static void free_ioctx_reqs(struct percpu_ref *ref) if (ctx->rq_wait && atomic_dec_and_test(&ctx->rq_wait->count)) complete(&ctx->rq_wait->comp); - INIT_WORK(&ctx->free_work, free_ioctx); - schedule_work(&ctx->free_work); + /* Synchronize against RCU protected table->table[] dereferences */ + call_rcu(&ctx->free_rcu, free_ioctx_rcufn); } /* @@ -838,7 +853,7 @@ static int kill_ioctx(struct mm_struct *mm, struct kioctx *ctx, table->table[ctx->id] = NULL; spin_unlock(&mm->ioctx_lock); - /* percpu_ref_kill() will do the necessary call_rcu() */ + /* free_ioctx_reqs() will do the necessary RCU synchronization */ wake_up_all(&ctx->wait); /* -- 2.9.5