Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755068Ab2K3AgN (ORCPT ); Thu, 29 Nov 2012 19:36:13 -0500 Received: from LGEMRELSE1Q.lge.com ([156.147.1.111]:57110 "EHLO LGEMRELSE1Q.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754414Ab2K3AgM (ORCPT ); Thu, 29 Nov 2012 19:36:12 -0500 X-AuditID: 9c93016f-b7b86ae000003a75-e3-50b7ff7be681 Date: Fri, 30 Nov 2012 09:36:09 +0900 From: Minchan Kim To: Nitin Gupta Cc: Greg KH , Jerome Marchand , Seth Jennings , Konrad Rzeszutek Wilk , Dan Carpenter , Sam Hansen , Linux Driver Project , linux-kernel Subject: Re: [PATCH v3] zram: fix invalid memory references during disk write Message-ID: <20121130003609.GA18630@blaptop> References: <1354180728-1958-1-git-send-email-ngupta@vflare.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1354180728-1958-1-git-send-email-ngupta@vflare.org> User-Agent: Mutt/1.5.21 (2010-09-15) X-Brightmail-Tracker: AAAAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4843 Lines: 152 Hi Greg, I would like to tidy zram_bvec_write up but it needs more churn than needed to fix this bug and makes review hard. So I want you to pick up this patch asap because it's a candidate of stable. Thanks. On Thu, Nov 29, 2012 at 01:18:48AM -0800, Nitin Gupta wrote: > Changelog v3 vs v2: > - Further changes to changelog message to explain the bug case > of incorrect use of kunmapped buffer > Changelog v2 vs v1: > - Changelog message now correctly explains the problem > > Fixes a bug introduced by commit c8f2f0db1 ("zram: Fix handling > of incompressible pages") which caused invalid memory references > during disk write. Invalid references could occur in two cases: > - Incoming data expands on compression: In this case, reference was > made to kunmap()'ed bio page. > - Partial (non PAGE_SIZE) write with incompressible data: In this > case, reference was made to a kfree()'ed buffer. > > Fixes bug 50081: > https://bugzilla.kernel.org/show_bug.cgi?id=50081 > > Signed-off-by: Nitin Gupta > Reported-by: Mihail Kasadjikov > Reported-by: Tomas M > Reviewed-by: Minchan Kim > --- > drivers/staging/zram/zram_drv.c | 39 ++++++++++++++++++++++++--------------- > 1 file changed, 24 insertions(+), 15 deletions(-) > > diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c > index fb4a7c9..f2a73bd 100644 > --- a/drivers/staging/zram/zram_drv.c > +++ b/drivers/staging/zram/zram_drv.c > @@ -265,7 +265,7 @@ out_cleanup: > static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index, > int offset) > { > - int ret; > + int ret = 0; > size_t clen; > unsigned long handle; > struct page *page; > @@ -286,10 +286,8 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index, > goto out; > } > ret = zram_decompress_page(zram, uncmem, index); > - if (ret) { > - kfree(uncmem); > + if (ret) > goto out; > - } > } > > /* > @@ -302,16 +300,18 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index, > > user_mem = kmap_atomic(page); > > - if (is_partial_io(bvec)) > + if (is_partial_io(bvec)) { > memcpy(uncmem + offset, user_mem + bvec->bv_offset, > bvec->bv_len); > - else > + kunmap_atomic(user_mem); > + user_mem = NULL; > + } else { > uncmem = user_mem; > + } > > if (page_zero_filled(uncmem)) { > - kunmap_atomic(user_mem); > - if (is_partial_io(bvec)) > - kfree(uncmem); > + if (!is_partial_io(bvec)) > + kunmap_atomic(user_mem); > zram_stat_inc(&zram->stats.pages_zero); > zram_set_flag(zram, index, ZRAM_ZERO); > ret = 0; > @@ -321,9 +321,11 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index, > ret = lzo1x_1_compress(uncmem, PAGE_SIZE, src, &clen, > zram->compress_workmem); > > - kunmap_atomic(user_mem); > - if (is_partial_io(bvec)) > - kfree(uncmem); > + if (!is_partial_io(bvec)) { > + kunmap_atomic(user_mem); > + user_mem = NULL; > + uncmem = NULL; > + } > > if (unlikely(ret != LZO_E_OK)) { > pr_err("Compression failed! err=%d\n", ret); > @@ -332,8 +334,10 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index, > > if (unlikely(clen > max_zpage_size)) { > zram_stat_inc(&zram->stats.bad_compress); > - src = uncmem; > clen = PAGE_SIZE; > + src = NULL; > + if (is_partial_io(bvec)) > + src = uncmem; > } > > handle = zs_malloc(zram->mem_pool, clen); > @@ -345,7 +349,11 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index, > } > cmem = zs_map_object(zram->mem_pool, handle, ZS_MM_WO); > > + if ((clen == PAGE_SIZE) && !is_partial_io(bvec)) > + src = kmap_atomic(page); > memcpy(cmem, src, clen); > + if ((clen == PAGE_SIZE) && !is_partial_io(bvec)) > + kunmap_atomic(src); > > zs_unmap_object(zram->mem_pool, handle); > > @@ -358,9 +366,10 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index, > if (clen <= PAGE_SIZE / 2) > zram_stat_inc(&zram->stats.good_compress); > > - return 0; > - > out: > + if (is_partial_io(bvec)) > + kfree(uncmem); > + > if (ret) > zram_stat64_inc(zram, &zram->stats.failed_writes); > return ret; > -- > 1.7.10.4 > > -- > 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/ -- Kind regards, Minchan Kim -- 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/