FAILED: patch "[PATCH] statmount: don't call path_put() under namespace semaphore" failed to apply to 6.12-stable tree

[<gregkh@linuxfoundation.org>]

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;