From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Hansen Subject: [PATCH 01/23] rearrange may_open() to be r/o friendly Date: Wed, 11 Jul 2007 17:17:11 -0700 Message-ID: <20070712001711.ED55C482@kernel> References: <20070712001710.654CD9ED@kernel> Cc: linux-fsdevel@vger.kernel.org, viro@zeniv.linux.org.uk, hch@infradead.org, Dave Hansen To: linux-kernel@vger.kernel.org Return-path: Received: from e32.co.us.ibm.com ([32.97.110.150]:36121 "EHLO e32.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934857AbXGLARO (ORCPT ); Wed, 11 Jul 2007 20:17:14 -0400 In-Reply-To: <20070712001710.654CD9ED@kernel> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org may_open() calls vfs_permission() before it does checks for IS_RDONLY(inode). It checks _again_ inside of vfs_permission(). The check inside of vfs_permission() is going away eventually. With the mnt_want/drop_write() functions, all of the r/o checks (except for this one) are consistently done before calling permission(). Because of this, I'd like to use permission() to hold a debugging check to make sure that the mnt_want/drop_write() calls are actually being made. So, to do this: 1. remove the IS_RDONLY() check from permission() 2. enforce that you must mnt_want_write() before even calling permission() 3. enable a debugging in permission() We need to rearrange may_open(). Here's the patch. --- lxc-dave/fs/namei.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff -puN fs/namei.c~rearrange-permission-and-ro-checks-in-may_open fs/namei.c --- lxc/fs/namei.c~rearrange-permission-and-ro-checks-in-may_open 2007-07-10 12:46:01.000000000 -0700 +++ lxc-dave/fs/namei.c 2007-07-10 12:46:01.000000000 -0700 @@ -228,6 +228,10 @@ int permission(struct inode *inode, int { umode_t mode = inode->i_mode; int retval, submask; + struct vfsmount *mnt = NULL; + + if (nd) + mnt = nd->mnt; if (mask & MAY_WRITE) { @@ -252,7 +256,7 @@ int permission(struct inode *inode, int * the fs is mounted with the "noexec" flag. */ if ((mask & MAY_EXEC) && S_ISREG(mode) && (!(mode & S_IXUGO) || - (nd && nd->mnt && (nd->mnt->mnt_flags & MNT_NOEXEC)))) + (mnt && (mnt->mnt_flags & MNT_NOEXEC)))) return -EACCES; /* Ordinary permission routines do not understand MAY_APPEND. */ @@ -1546,10 +1550,6 @@ int may_open(struct nameidata *nd, int a if (S_ISDIR(inode->i_mode) && (flag & FMODE_WRITE)) return -EISDIR; - error = vfs_permission(nd, acc_mode); - if (error) - return error; - /* * FIFO's, sockets and device files are special: they don't * actually live on the filesystem itself, and as such you @@ -1564,6 +1564,10 @@ int may_open(struct nameidata *nd, int a flag &= ~O_TRUNC; } else if (IS_RDONLY(inode) && (flag & FMODE_WRITE)) return -EROFS; + + error = vfs_permission(nd, acc_mode); + if (error) + return error; /* * An append-only file must be opened in append mode for writing. */ _