Return-Path: linux-nfs-owner@vger.kernel.org Received: from casper.infradead.org ([85.118.1.10]:45781 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754072AbaHGHVk (ORCPT ); Thu, 7 Aug 2014 03:21:40 -0400 From: Christoph Hellwig To: Trond Myklebust Cc: linux-nfs@vger.kernel.org Subject: [PATCH 11/17] pnfs/blocklayout: correctly decrement extent length Date: Thu, 7 Aug 2014 09:23:43 +0200 Message-Id: <1407396229-4785-12-git-send-email-hch@lst.de> In-Reply-To: <1407396229-4785-1-git-send-email-hch@lst.de> References: <1407396229-4785-1-git-send-email-hch@lst.de> Sender: linux-nfs-owner@vger.kernel.org List-ID: When we do non-page sized reads we can underflow the extent_length variable and read incorrect data. Fix the extent_length calculation and change to defensive <= checks for the extent length in the read and write path. Signed-off-by: Christoph Hellwig --- fs/nfs/blocklayout/blocklayout.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/fs/nfs/blocklayout/blocklayout.c b/fs/nfs/blocklayout/blocklayout.c index 5427ae7..87a633d 100644 --- a/fs/nfs/blocklayout/blocklayout.c +++ b/fs/nfs/blocklayout/blocklayout.c @@ -272,7 +272,7 @@ bl_read_pagelist(struct nfs_pgio_header *hdr) isect = (sector_t) (f_offset >> SECTOR_SHIFT); /* Code assumes extents are page-aligned */ for (i = pg_index; i < hdr->page_array.npages; i++) { - if (!extent_length) { + if (extent_length <= 0) { /* We've used up the previous extent */ bl_put_extent(be); bl_put_extent(cow_read); @@ -303,6 +303,7 @@ bl_read_pagelist(struct nfs_pgio_header *hdr) f_offset += pg_len; bytes_left -= pg_len; isect += (pg_offset >> SECTOR_SHIFT); + extent_length -= (pg_offset >> SECTOR_SHIFT); } else { pg_offset = 0; pg_len = PAGE_CACHE_SIZE; @@ -333,7 +334,7 @@ bl_read_pagelist(struct nfs_pgio_header *hdr) } } isect += (pg_len >> SECTOR_SHIFT); - extent_length -= PAGE_CACHE_SECTORS; + extent_length -= (pg_len >> SECTOR_SHIFT); } if ((isect << SECTOR_SHIFT) >= header->inode->i_size) { hdr->res.eof = 1; @@ -797,7 +798,7 @@ next_page: /* Middle pages */ pg_index = header->args.pgbase >> PAGE_CACHE_SHIFT; for (i = pg_index; i < header->page_array.npages; i++) { - if (!extent_length) { + if (extent_length <= 0) { /* We've used up the previous extent */ bl_put_extent(be); bl_put_extent(cow_read); -- 1.9.1