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

PATCH New [email protected] 2 participants 2 messages Oct 15, 2025 – Oct 16, 2025

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author maintainer
#0 lore raw

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 <[email protected]>.

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 '<[email protected]>' --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 <[email protected]>
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 [email protected] # v6.8+
Signed-off-by Christian Brauner <[email protected]>
fs/namespace.c +3 -5
index ba3e5215b636..993983a76853 100644
@@ -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;
maintainer
#1 lore raw

PATCH 1/1 statmount: don't call path_put() under namespace semaphore

From: Christian Brauner <[email protected]>

[ Upstream commit e8c84e2082e69335f66c8ade4895e80ec270d7c4 ]

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 [email protected] # v6.8+
Signed-off-by Christian Brauner <[email protected]>
Signed-off-by Sasha Levin <[email protected]>
---
 fs/namespace.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)
fs/namespace.c +3 -5
index c8519302f5824..274db35ca5abd 100644
@@ -5200,7 +5200,6 @@ 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;
 

@@ -5212,7 +5211,7 @@ 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;
 

@@ -5221,15 +5220,13 @@ 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;
 
 	err = security_sb_statfs(s->mnt->mnt_root);
 	if (err)
 		return err;
-
-	s->root = root;
 	if (s->mask & STATMOUNT_SB_BASIC)
 		statmount_sb_basic(s);
 

@@ -5406,6 +5403,7 @@ 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;
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