Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755762Ab3HEXnN (ORCPT ); Mon, 5 Aug 2013 19:43:13 -0400 Received: from bedivere.hansenpartnership.com ([66.63.167.143]:59419 "EHLO bedivere.hansenpartnership.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755069Ab3HEXnL (ORCPT ); Mon, 5 Aug 2013 19:43:11 -0400 Message-ID: <1375746189.18481.23.camel@dabdike.int.hansenpartnership.com> Subject: Re: [PATCH] [SCSI] sg: Fix user memory corruption when SG_IO is interrupted by a signal From: James Bottomley To: Roland Dreier Cc: Jens Axboe , Doug Gilbert , Costa Sapuntzakis , =?ISO-8859-1?Q?J=F6rn?= Engel , "linux-kernel@vger.kernel.org" , linux-scsi Date: Mon, 05 Aug 2013 16:43:09 -0700 In-Reply-To: References: <1375740121-23350-1-git-send-email-roland@kernel.org> <1375745462.18481.22.camel@dabdike.int.hansenpartnership.com> Content-Type: text/plain; charset="ISO-8859-15" X-Mailer: Evolution 3.8.3 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2472 Lines: 59 On Mon, 2013-08-05 at 16:38 -0700, Roland Dreier wrote: > On Mon, Aug 5, 2013 at 4:31 PM, James Bottomley > wrote: > > I agree with the analysis. The fix is a bit draconian, though. A > > workqueue actually runs in a kernel thread and there's a simple test for > > that (!current->mm), so how about this instead (which is much less > > intrusive) > > > --- > > > diff --git a/fs/bio.c b/fs/bio.c > > index 94bbc04..e2ab39c 100644 > > --- a/fs/bio.c > > +++ b/fs/bio.c > > @@ -1045,12 +1045,22 @@ static int __bio_copy_iov(struct bio *bio, struct bio_vec *iovecs, > > int bio_uncopy_user(struct bio *bio) > > { > > struct bio_map_data *bmd = bio->bi_private; > > - int ret = 0; > > + struct bio_vec *bvec; > > + int ret = 0, i; > > > > - if (!bio_flagged(bio, BIO_NULL_MAPPED)) > > - ret = __bio_copy_iov(bio, bmd->iovecs, bmd->sgvecs, > > - bmd->nr_sgvecs, bio_data_dir(bio) == READ, > > - 0, bmd->is_our_pages); > > + if (!bio_flagged(bio, BIO_NULL_MAPPED)) { > > + /* > > + * if we're in a workqueue, the request is orphaned, so > > + * don't copy into the kernel address space, just free > > + */ > > + if (current->mm) > > + ret = __bio_copy_iov(bio, bmd->iovecs, bmd->sgvecs, > > + bmd->nr_sgvecs, bio_data_dir(bio) == READ, > > + 0, bmd->is_our_pages); > > + else if (bmd->is_our_pages) > > + bio_for_each_segment_all(bvec, bio, i) > > + __free_page(bvec->bv_page); > > + } > > bio_free_map_data(bmd); > > bio_put(bio); > > return ret; > > Yes, looks reasonable -- I can't think of any reason why anyone would > ever want the bio code to copy to a random userspace address space. > > Acked-by: Roland Dreier You did all the work ... just replace this patch with your previous one and keep the original tags. (test it first, of course ...) James -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/