The patch below does not apply to the 6.12-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y git checkout FETCH_HEAD git cherry-pick -x e8c84e2082e69335f66c8ade4895e80ec270d7c4 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025101533-mutt-routing-a332@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From e8c84e2082e69335f66c8ade4895e80ec270d7c4 Mon Sep 17 00:00:00 2001 From: Christian Brauner brauner@kernel.org Date: Fri, 19 Sep 2025 17:03:51 +0200 Subject: [PATCH] statmount: don't call path_put() under namespace semaphore

Massage statmount() and make sure we don't call path_put() under the namespace semaphore. If we put the last reference we're fscked.

Fixes: 46eae99ef733 ("add statmount(2) syscall") Cc: stable@vger.kernel.org # v6.8+ Signed-off-by: Christian Brauner brauner@kernel.org

diff --git a/fs/namespace.c b/fs/namespace.c index ba3e5215b636..993983a76853 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -5708,7 +5708,6 @@ static int grab_requested_root(struct mnt_namespace *ns, struct path *root) static int do_statmount(struct kstatmount *s, u64 mnt_id, u64 mnt_ns_id, struct mnt_namespace *ns) { - struct path root __free(path_put) = {}; struct mount *m; int err;

@@ -5720,7 +5719,7 @@ static int do_statmount(struct kstatmount *s, u64 mnt_id, u64 mnt_ns_id, if (!s->mnt) return -ENOENT;

- err = grab_requested_root(ns, &root); + err = grab_requested_root(ns, &s->root); if (err) return err;

@@ -5729,7 +5728,7 @@ static int do_statmount(struct kstatmount *s, u64 mnt_id, u64 mnt_ns_id, * mounts to show users. */ m = real_mount(s->mnt); - if (!is_path_reachable(m, m->mnt.mnt_root, &root) && + if (!is_path_reachable(m, m->mnt.mnt_root, &s->root) && !ns_capable_noaudit(ns->user_ns, CAP_SYS_ADMIN)) return -EPERM;

@@ -5737,8 +5736,6 @@ static int do_statmount(struct kstatmount *s, u64 mnt_id, u64 mnt_ns_id, if (err) return err;

- s->root = root; - /* * Note that mount properties in mnt->mnt_flags, mnt->mnt_idmap * can change concurrently as we only hold the read-side of the @@ -5960,6 +5957,7 @@ SYSCALL_DEFINE4(statmount, const struct mnt_id_req __user *, req, if (!ret) ret = copy_statmount_to_user(ks); kvfree(ks->seq.buf); + path_put(&ks->root); if (retry_statmount(ret, &seq_size)) goto retry; return ret;