diff options
| author | Aleksa Sarai <cyphar@cyphar.com> | 2025-08-08 03:55:05 +1000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-08-28 16:34:26 +0200 |
| commit | 69dbdc711d9130136824e3830191a6afffa0a1f0 (patch) | |
| tree | e507ac5c7ab1d654c3271d480765ba7ccf704b46 | |
| parent | 23a94fc0fcd2f09d626557a7f7fbfbd9ac0f17ab (diff) | |
open_tree_attr: do not allow id-mapping changes without OPEN_TREE_CLONE
commit 9308366f062129d52e0ee3f7a019f7dd41db33df upstream.
As described in commit 7a54947e727b ('Merge patch series "fs: allow
changing idmappings"'), open_tree_attr(2) was necessary in order to
allow for a detached mount to be created and have its idmappings changed
without the risk of any racing threads operating on it. For this reason,
mount_setattr(2) still does not allow for id-mappings to be changed.
However, there was a bug in commit 2462651ffa76 ("fs: allow changing
idmappings") which allowed users to bypass this restriction by calling
open_tree_attr(2) *without* OPEN_TREE_CLONE.
can_idmap_mount() prevented this bug from allowing an attached
mountpoint's id-mapping from being modified (thanks to an is_anon_ns()
check), but this still allows for detached (but visible) mounts to have
their be id-mapping changed. This risks the same UAF and locking issues
as described in the merge commit, and was likely unintentional.
Fixes: 2462651ffa76 ("fs: allow changing idmappings")
Cc: stable@vger.kernel.org # v6.15+
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
Link: https://lore.kernel.org/20250808-open_tree_attr-bugfix-idmap-v1-1-0ec7bc05646c@cyphar.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | fs/namespace.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/fs/namespace.c b/fs/namespace.c index 54c59e091919..ea724ad3d113 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -5302,7 +5302,8 @@ SYSCALL_DEFINE5(open_tree_attr, int, dfd, const char __user *, filename, int ret; struct mount_kattr kattr = {}; - kattr.kflags = MOUNT_KATTR_IDMAP_REPLACE; + if (flags & OPEN_TREE_CLONE) + kattr.kflags = MOUNT_KATTR_IDMAP_REPLACE; if (flags & AT_RECURSIVE) kattr.kflags |= MOUNT_KATTR_RECURSE; |