Return-Path: Received: from mail-pa0-f45.google.com ([209.85.220.45]:32842 "EHLO mail-pa0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752878AbbJPJXD (ORCPT ); Fri, 16 Oct 2015 05:23:03 -0400 Received: by pabrc13 with SMTP id rc13so115742926pab.0 for ; Fri, 16 Oct 2015 02:23:02 -0700 (PDT) Subject: [PATCH 1/2] nfs/blocklayout: Fix bad using of page offset in bl_read_pagelist To: Trond Myklebust References: <55FF77DD.8070807@gmail.com> <561CFD01.3080201@gmail.com> <561E01BA.4040109@gmail.com> <561F9FBA.7090501@gmail.com> Cc: "linux-nfs@vger.kernel.org" , kinglongmee@gmail.com From: Kinglong Mee Message-ID: <5620C1EA.9020302@gmail.com> Date: Fri, 16 Oct 2015 17:22:50 +0800 MIME-Version: 1.0 In-Reply-To: <561F9FBA.7090501@gmail.com> Content-Type: text/plain; charset=utf-8 Sender: linux-nfs-owner@vger.kernel.org List-ID: Blocklayout uses file offset for the read-back page's offset of first writing, it's definitely wrong, it writes data to bad address of page that cause userspace application segment fault. It must be the page base stored in header->args.pgbase. Also, the pg_offset has no influence with isect and extent length. Note: The offset of the non-first page is always zero. Ps: A test program will segment fault at read() as, #define _GNU_SOURCE #include #include #include #include #include #include #include int main(int argc, char **argv) { char buf[2049]; char *filename = NULL; int fd = -1; if (argc < 2) { printf("Usage: %s filename\n", argv[0]); return 0; } filename = argv[1]; fd = open(filename, O_RDONLY | O_DIRECT); if (fd < 0) { printf("Open %s fail: %m\n", filename); return 1; } lseek(fd, 2048, SEEK_SET); if (read(fd, buf, sizeof(buf) - 1) != (sizeof(buf) - 1)) printf("Read 4096 bityes data from %s fail: %m\n", filename); out: close(fd); return 0; } Signed-off-by: Kinglong Mee --- fs/nfs/blocklayout/blocklayout.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) diff --git a/fs/nfs/blocklayout/blocklayout.c b/fs/nfs/blocklayout/blocklayout.c index 9cd4eb3..ddd0138 100644 --- a/fs/nfs/blocklayout/blocklayout.c +++ b/fs/nfs/blocklayout/blocklayout.c @@ -229,7 +229,7 @@ bl_read_pagelist(struct nfs_pgio_header *header) struct parallel_io *par; loff_t f_offset = header->args.offset; size_t bytes_left = header->args.count; - unsigned int pg_offset, pg_len; + unsigned int pg_offset = header->args.pgbase, pg_len; struct page **pages = header->args.pages; int pg_index = header->args.pgbase >> PAGE_CACHE_SHIFT; const bool is_dio = (header->dreq != NULL); @@ -262,7 +262,6 @@ bl_read_pagelist(struct nfs_pgio_header *header) extent_length = be.be_length - (isect - be.be_f_offset); } - pg_offset = f_offset & ~PAGE_CACHE_MASK; if (is_dio) { if (pg_offset + bytes_left > PAGE_CACHE_SIZE) pg_len = PAGE_CACHE_SIZE - pg_offset; @@ -273,9 +272,6 @@ bl_read_pagelist(struct nfs_pgio_header *header) pg_len = PAGE_CACHE_SIZE; } - isect += (pg_offset >> SECTOR_SHIFT); - extent_length -= (pg_offset >> SECTOR_SHIFT); - if (is_hole(&be)) { bio = bl_submit_bio(READ, bio); /* Fill hole w/ zeroes w/o accessing device */ @@ -301,6 +297,7 @@ bl_read_pagelist(struct nfs_pgio_header *header) extent_length -= (pg_len >> SECTOR_SHIFT); f_offset += pg_len; bytes_left -= pg_len; + pg_offset = 0; } if ((isect << SECTOR_SHIFT) >= header->inode->i_size) { header->res.eof = 1; -- 2.5.0