Unverified Commit 398840f8 authored Oct 28, 2020 by Aleksa Sarai Committed by Christian Brauner Dec 03, 2020

openat2: reject RESOLVE_BENEATH|RESOLVE_IN_ROOT



This was an oversight in the original implementation, as it makes no
sense to specify both scoping flags to the same openat2(2) invocation
(before this patch, the result of such an invocation was equivalent to
RESOLVE_IN_ROOT being ignored).

This is a userspace-visible ABI change, but the only user of openat2(2)
at the moment is LXC which doesn't specify both flags and so no
userspace programs will break as a result.

Fixes: fddb5d43 ("open: introduce openat2(2) syscall")
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Cc: <stable@vger.kernel.org> # v5.6+
Link: https://lore.kernel.org/r/20201027235044.5240-2-cyphar@cyphar.com


Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

parent b6505459

fs/open.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -1010,6 +1010,10 @@ inline int build_open_flags(const struct open_how how, struct open_flags op)
		if (how->resolve & ~VALID_RESOLVE_FLAGS)
		return -EINVAL;

		/* Scoping flags are mutually exclusive. */
		if ((how->resolve & RESOLVE_BENEATH) && (how->resolve & RESOLVE_IN_ROOT))
		return -EINVAL;

		/* Deal with the mode. */
		if (WILL_CREATE(flags)) {
		if (how->mode & ~S_IALLUGO)

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