Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752079Ab2K2JS5 (ORCPT ); Thu, 29 Nov 2012 04:18:57 -0500 Received: from mail-da0-f46.google.com ([209.85.210.46]:61626 "EHLO mail-da0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751138Ab2K2JSy (ORCPT ); Thu, 29 Nov 2012 04:18:54 -0500 From: Nitin Gupta To: Greg KH Cc: Jerome Marchand , Minchan Kim , Seth Jennings , Konrad Rzeszutek Wilk , Dan Carpenter , Sam Hansen , Linux Driver Project , linux-kernel Subject: [PATCH v3] zram: fix invalid memory references during disk write Date: Thu, 29 Nov 2012 01:18:48 -0800 Message-Id: <1354180728-1958-1-git-send-email-ngupta@vflare.org> X-Mailer: git-send-email 1.7.10.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4026 Lines: 134 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/