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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=gmail.com header.result=pass header_is_org_domain=yes Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933706AbeCGVse (ORCPT ); Wed, 7 Mar 2018 16:48:34 -0500 Received: from mail-wr0-f194.google.com ([209.85.128.194]:33804 "EHLO mail-wr0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933674AbeCGVse (ORCPT ); Wed, 7 Mar 2018 16:48:34 -0500 X-Google-Smtp-Source: AG47ELvUtY2PuGyA9bEjbr/6c/VhYUtLueApPMESIbUv9mObt0UYddJ7lv88WYWICvd0uVpOGNsBsA== Date: Wed, 7 Mar 2018 14:48:29 -0700 From: Nathan Chancellor To: Paul Lawrence Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, Ben Hutchings , Greg Kroah-Hartman , Arve =?iso-8859-1?B?SGr4bm5lduVn?= , Todd Kjos , Martijn Coenen , devel@driverdev.osuosl.org Subject: Re: [PATCH] staging: android: ashmem: Remove deadlock Message-ID: <20180307214829.GA15587@flashbox> References: <20180307214042.135109-1-paullawrence@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180307214042.135109-1-paullawrence@google.com> User-Agent: Mutt/1.9.3 (2018-01-21) 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: On Wed, Mar 07, 2018 at 01:40:30PM -0800, Paul Lawrence wrote: > Regression introduced in commit ce8a3a9e76d0193e2e8d74a06d275b3c324ca652 > ("staging: android: ashmem: Fix a race condition in pin ioctls") > causing deadlock. > > No need to hold ashmem_mutex while copying from user > > Stacks are: > > ashmem_mmap+0x53/0x400 drivers/staging/android/ashmem.c:379 > mmap_region+0x7dd/0xfd0 mm/mmap.c:1694 > do_mmap+0x57b/0xbe0 mm/mmap.c:1473 > > and > > lock_acquire+0x12e/0x410 kernel/locking/lockdep.c:3756 > __might_fault+0x14a/0x1d0 mm/memory.c:4014 > copy_from_user arch/x86/include/asm/uaccess.h:705 [inline] > ashmem_pin_unpin drivers/staging/android/ashmem.c:719 [inline] > > Signed-off-by: Paul Lawrence > Cc: # 4.9.x > Cc: # 4.4.x > Cc: # 3.18.x: ce8a3a9e76d01 > Cc: # 3.18.x > Cc: Ben Hutchings > --- > drivers/staging/android/ashmem.c | 8 +++----- > 1 file changed, 3 insertions(+), 5 deletions(-) > > diff --git a/drivers/staging/android/ashmem.c b/drivers/staging/android/ashmem.c > index 6dbba5aff191..8c55706c2cfa 100644 > --- a/drivers/staging/android/ashmem.c > +++ b/drivers/staging/android/ashmem.c > @@ -702,16 +702,14 @@ static int ashmem_pin_unpin(struct ashmem_area *asma, unsigned long cmd, > size_t pgstart, pgend; > int ret = -EINVAL; > > + if (unlikely(copy_from_user(&pin, p, sizeof(pin)))) > + return -EFAULT; > + > mutex_lock(&ashmem_mutex); > > if (unlikely(!asma->file)) > goto out_unlock; > > - if (unlikely(copy_from_user(&pin, p, sizeof(pin)))) { > - ret = -EFAULT; > - goto out_unlock; > - } > - > /* per custom, you can pass zero for len to mean "everything onward" */ > if (!pin.len) > pin.len = PAGE_ALIGN(asma->size) - pin.offset; > -- > 2.16.2.395.g2e18187dfd-goog > Hey Paul, Looks like this same patch is already in Greg's tree: https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git/commit/?id=740a5759bf222332fbb5eda42f89aa25ba38f9b2 Cheers! Nathan Chancellor