Messages in this thread Patch in this message | | | From | Linus Torvalds <> | Date | Mon, 20 Mar 2023 13:24:52 -0700 | Subject | Re: [PATCH] do_open(): Fix O_DIRECTORY | O_CREAT behavior |
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On Mon, Mar 20, 2023 at 12:27 PM Pedro Falcato <pedro.falcato@gmail.com> 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
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