make build_open_flags() treat O_CREAT | O_EXCL as implying O_NOFOLLOW

O_CREAT | O_EXCL means "-EEXIST if we run into a trailing symlink".
As it is, we might or might not have LOOKUP_FOLLOW in op->intent
in that case - that depends upon having O_NOFOLLOW in open flags.
It doesn't matter, since we won't be checking it in that case -
do_last() bails out earlier.

However, making sure it's not set (i.e. acting as if we had an explicit
O_NOFOLLOW) makes the behaviour more explicit and allows to reorder the
check for O_CREAT | O_EXCL in do_last() with the call of step_into()
immediately following it.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/namei.c b/fs/namei.c
index 6721c5f..6938d20 100644 (file)
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3396,22 +3396,17 @@ static int do_last(struct nameidata *nd,
        if (unlikely(error < 0))
                return error;
 
-       /*
-        * create/update audit record if it already exists.
-        */
-       audit_inode(nd->name, path.dentry, 0);
-
-       if (unlikely((open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT))) {
-               path_to_nameidata(&path, nd);
-               return -EEXIST;
-       }
-
        seq = 0;        /* out of RCU mode, so the value doesn't matter */
        inode = d_backing_inode(path.dentry);
 finish_lookup:
        error = step_into(nd, &path, 0, inode, seq);
        if (unlikely(error))
                return error;
+
+       if (unlikely((open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT))) {
+               audit_inode(nd->name, nd->path.dentry, 0);
+               return -EEXIST;
+       }
 finish_open:
        /* Why this, you ask?  _Now_ we might have grown LOOKUP_JUMPED... */
        error = complete_walk(nd);

diff --git a/fs/open.c b/fs/open.c
index 0788b37..e5227cd 100644 (file)
--- a/fs/open.c
+++ b/fs/open.c
@@ -1049,8 +1049,10 @@ inline int build_open_flags(const struct open_how *how, struct open_flags *op)
 
        if (flags & O_CREAT) {
                op->intent |= LOOKUP_CREATE;
-               if (flags & O_EXCL)
+               if (flags & O_EXCL) {
                        op->intent |= LOOKUP_EXCL;
+                       flags |= O_NOFOLLOW;
+               }
        }
 
        if (flags & O_DIRECTORY)