From mboxrd@z Thu Jan 1 00:00:00 1970 From: piaojun Date: Thu, 17 Nov 2016 19:58:37 +0800 Subject: [Ocfs2-devel] ocfs2: fix sparse file & data ordering issue in direct io In-Reply-To: <20160309102505.GA15030@mwanda> References: <20160309102505.GA15030@mwanda> Message-ID: <582D9B6D.8080205@huawei.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: ocfs2-devel@oss.oracle.com Hi Carpenter, I guess this may cause illegal memory access error as follows: generic_perform_write --a_ops->write_begin(file, mapping, pos, bytes, flags, &page, &fsdata); --ocfs2_write_begin_nolock --ocfs2_grab_pages_for_write --return -EAGAIN if not enough pages --'fsdata' will be uninitialized --a_ops->write_end(file, mapping, pos, bytes, copied, page, fsdata); --ocfs2_write_end_nolock --the access of wc->w_di_bh->b_data will cause error. if so, I suggest not eating error code and let upper level to handle this problem. On 2016-3-9 18:25, Dan Carpenter wrote: > Hello Ryan Ding, > > The patch fbe25fb91af5: "ocfs2: fix sparse file & data ordering issue > in direct io" from Feb 25, 2016, leads to the following static > checker warning: > > fs/ocfs2/aops.c:2242 ocfs2_dio_get_block() > error: potentially dereferencing uninitialized 'wc'. > > fs/ocfs2/aops.c > 2235 > 2236 ret = ocfs2_write_begin_nolock(inode->i_mapping, pos, len, > 2237 OCFS2_WRITE_DIRECT, NULL, > 2238 (void **)&wc, di_bh, NULL); > ^^^^^^^^^^^^ > > See commit 5cffff9e2986 ('ocfs2: Fix ocfs2_page_mkwrite()') for an > explanation why a zero return here does not imply that "wc" has been > initialized. > > 2239 if (ret) { > 2240 mlog_errno(ret); > 2241 goto unlock; > 2242 } > 2243 > 2244 desc = &wc->w_desc[0]; > 2245 > 2246 p_blkno = ocfs2_clusters_to_blocks(inode->i_sb, desc->c_phys); > > regards, > dan carpenter > > _______________________________________________ > Ocfs2-devel mailing list > Ocfs2-devel at oss.oracle.com > https://oss.oracle.com/mailman/listinfo/ocfs2-devel > >