[PATCH] open: make RESOLVE_CACHED correctly test for O_TMPFILE

[PATCH] open: make RESOLVE_CACHED correctly test for O_TMPFILE

[Aleksa Sarai]

O_TMPFILE is actually __O_TMPFILE|O_DIRECTORY. This means that the old
fast-path check for RESOLVE_CACHED would reject all users passing
O_DIRECTORY with -EAGAIN, when in fact the intended test was to check
for __O_TMPFILE.

Cc: stable@vger.kernel.org # v5.12+
Fixes: 99668f618062 ("fs: expose LOOKUP_CACHED through openat2() RESOLVE_CACHED")
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
---
 fs/open.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/open.c b/fs/open.c
index b8883ec286f5..2634047c9e9f 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -1337,7 +1337,7 @@ inline int build_open_flags(const struct open_how *how, struct open_flags *op)
 		lookup_flags |= LOOKUP_IN_ROOT;
 	if (how->resolve & RESOLVE_CACHED) {
 		/* Don't bother even trying for create/truncate/tmpfile open */
-		if (flags & (O_TRUNC | O_CREAT | O_TMPFILE))
+		if (flags & (O_TRUNC | O_CREAT | __O_TMPFILE))
 			return -EAGAIN;
 		lookup_flags |= LOOKUP_CACHED;
 	}

---
base-commit: bf5ad7af0516cb47121dae1b1c160e4385615274
change-id: 20230806-resolve_cached-o_tmpfile-978cb238bd68

Best regards,
-- 
Aleksa Sarai <cyphar@cyphar.com>

Re: [PATCH] open: make RESOLVE_CACHED correctly test for O_TMPFILE

[Christian Brauner]

On Sun, 06 Aug 2023 02:11:58 +1000, Aleksa Sarai wrote:
> O_TMPFILE is actually __O_TMPFILE|O_DIRECTORY. This means that the old
> fast-path check for RESOLVE_CACHED would reject all users passing
> O_DIRECTORY with -EAGAIN, when in fact the intended test was to check
> for __O_TMPFILE.
> 
> 

Applied to the vfs.fixes branch of the vfs/vfs.git tree.
Patches in the vfs.fixes branch should appear in linux-next soon.

Please report any outstanding bugs that were missed during review in a
new review to the original patch series allowing us to drop it.

It's encouraged to provide Acked-bys and Reviewed-bys even though the
patch has now been applied. If possible patch trailers will be updated.

Note that commit hashes shown below are subject to change due to rebase,
trailer updates or similar. If in doubt, please check the listed branch.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
branch: vfs.fixes

[1/1] open: make RESOLVE_CACHED correctly test for O_TMPFILE
      https://git.kernel.org/vfs/vfs/c/7c62794bc37f

Re: [PATCH] open: make RESOLVE_CACHED correctly test for O_TMPFILE

[Christian Brauner]

On Sat, Aug 05, 2023 at 07:17:54PM +0200, Christian Brauner wrote:
> On Sun, 06 Aug 2023 02:11:58 +1000, Aleksa Sarai wrote:
> > O_TMPFILE is actually __O_TMPFILE|O_DIRECTORY. This means that the old
> > fast-path check for RESOLVE_CACHED would reject all users passing
> > O_DIRECTORY with -EAGAIN, when in fact the intended test was to check
> > for __O_TMPFILE.

And afaict, io_uring has the same problem in

static bool io_openat_force_async(struct io_open *open)
{
        /*
         * Don't bother trying for O_TRUNC, O_CREAT, or O_TMPFILE open,
         * it'll always -EAGAIN
         */
        return open->how.flags & (O_TRUNC | O_CREAT | O_TMPFILE);
}

always forcing O_DIRECTORY lookups to go async. So that needs another
fix.