On Mon, Mar 20, 2023 at 12:27 PM Pedro Falcato <pedro.falcato@xxxxxxxxx> wrote:
>
> 1) Pre v5.7 Linux did the open-dir-if-exists-else-create-regular-file
> we all know and """love""".
So I think we should fall back to this as a last resort, as a "well,
it's our historical behavior".
> 2) Post 5.7, we started returning this buggy -ENOTDIR error, even when
> successfully creating a file.
Yeah, I think this is the worst of the bunch and has no excuse (unless
some crazy program has started depending on it, which sounds really
*really* unlikely).
> 3) NetBSD just straight up returns EINVAL on open(O_DIRECTORY | O_CREAT)
> 4) FreeBSD's open(O_CREAT | O_DIRECTORY) succeeds if the file exists
> and is a directory. Fails with -ENOENT if it falls onto the "O_CREAT"
> path (i.e it doesn't try to create the file at all, just ENOENT's;
> this changed relatively recently, in 2015)
Either of these sound sensible to me.
I suspect (3) is the clearest case.
And (4) might be warranted just because it's closer to what we used to
do, and it's *possible* that somebody happens to use O_DIRECTORY |
O_CREAT on directories that exist, and never noticed how broken that
was.
And (4) has another special case: O_EXCL. Because I'm really hoping
that O_DIRECTORY | O_EXCL will always fail.
Is the proper patch something along the lines of this?
--- a/fs/open.c
+++ b/fs/open.c
@@ -1186,6 +1186,8 @@ inline int build_open_flags(const struct
open_how *how, struct open_flags *op)
/* Deal with the mode. */
if (WILL_CREATE(flags)) {
+ if (flags & O_DIRECTORY)
+ return -EINVAL;
if (how->mode & ~S_IALLUGO)
return -EINVAL;
op->mode = how->mode | S_IFREG;
I dunno. Not tested, not thought about very much.
What about O_PATH? I guess it's fine to create a file and only get a
path fd to the result?
Linus
