[PATCH v2] audit: vfs: fix audit records error when write to a file

[hujianyang]

Changes from v1:

   * Move audit_inode() to the beginning of O_CREAT case in
     lookup_open() to avoid missing audit for ROFS error. This
     lack is spotted by Jeff Layton <jeff.layton@xxxxxxxxxxxxxxx>

commit 33e2208acfc1

audit: vfs: fix audit_inode call in O_CREAT case of do_last

fix a regression in auditing of open(..., O_CREAT) syscalls but
introduce a new problem which lead the records of write operation
confusion.

This error can be reproduced by these steps:

	touch /etc/test
	echo "-w /etc/test" >>/etc/audit/audit.rules
	/etc/init.d/auditd restart

	echo "abc" >> /etc/test

audit_name records are:

type=PATH msg=audit(1409764556.196:67): item=0 name="/etc/" inode=5097 dev=00:01 mode=040755 ouid=0 ogid=0 rdev=00:00 nametype=PARENT
type=PATH msg=audit(1409764556.196:67): item=1 name=(null) inode=23161 dev=00:01 mode=0100644 ouid=0 ogid=0 rdev=00:00 nametype=NORMAL
type=PATH msg=audit(1409764556.196:67): item=2 name=(null) inode=23161 dev=00:01 mode=0100644 ouid=0 ogid=0 rdev=00:00 nametype=NORMAL

but if we revert commit 33e2208acfc1, records are correct:

type=PATH msg=audit(1409763058.192:219): item=0 name="/etc/test" inode=1275 dev=00:01 mode=0100644 ouid=0 ogid=0 rdev=00:00 nametype=NORMAL

We shouldn't leave audit_inode(.., LOOKUP_PARENT) in O_CREAT case
of do_last() because this branch don't really know if vfs need to
create a new file. There is no need to do vfs_create() if we open
an existing file with O_CREAT flag and write to it. But this
audit_inode() in O_CREAT case will record a msg as we create a new
file and confuse the records of write.

This patch moves the audit for create operation to where a file
really need to be created, the O_CREAT case in lookup_open().
We have to add the pointer of struct filename as a parameter of
lookup_open(). By doing this, the records of both create and write
are correct.

Signed-off-by: hujianyang <hujianyang@xxxxxxxxxx>
---
 fs/namei.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index a996bb4..ca4a831 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2808,7 +2808,8 @@ looked_up:
 static int lookup_open(struct nameidata *nd, struct path *path,
 			struct file *file,
 			const struct open_flags *op,
-			bool got_write, int *opened)
+			bool got_write, int *opened,
+			struct filename *name)
 {
 	struct dentry *dir = nd->path.dentry;
 	struct inode *dir_inode = dir->d_inode;
@@ -2841,6 +2842,8 @@ static int lookup_open(struct nameidata *nd, struct path *path,
 	/* Negative dentry, just create the file */
 	if (!dentry->d_inode && (op->open_flag & O_CREAT)) {
 		umode_t mode = op->mode;
+
+		audit_inode(name, dir, LOOKUP_PARENT);
 		if (!IS_POSIXACL(dir->d_inode))
 			mode &= ~current_umask();
 		/*
@@ -2926,7 +2929,6 @@ static int do_last(struct nameidata *nd, struct path *path,
 		if (error)
 			return error;

-		audit_inode(name, dir, LOOKUP_PARENT);
 		error = -EISDIR;
 		/* trailing slashes? */
 		if (nd->last.name[nd->last.len])
@@ -2945,7 +2947,7 @@ retry_lookup:
 		 */
 	}
 	mutex_lock(&dir->d_inode->i_mutex);
-	error = lookup_open(nd, path, file, op, got_write, opened);
+	error = lookup_open(nd, path, file, op, got_write, opened, name);
 	mutex_unlock(&dir->d_inode->i_mutex);

 	if (error <= 0) {
-- 
1.8.5.5

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