>From 26907be24e631329ba963d66196fe4f5d0863388 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Thu, 29 Jan 2026 14:52:22 +0100 Subject: [PATCH] namespace: fix proc mount iteration The m->index isn't updated when m->show() overflows and retains its value before the current mount causing a restart to start at the same value. If that happens in short order to due a quickly expanding mount table this would cause the same mount to be shown again and again. Ensure that *pos always equals the mount id of the mount that was returned by start/next. On restart after overflow mnt_find_id_at(*pos) finds the exact mount. This should avoid duplicates, avoid skips and should handle concurrent modification just fine. Cc: Fixed: 2eea9ce4310d8 ("mounts: keep list of mounts in an rbtree") Signed-off-by: Christian Brauner --- fs/namespace.c | 20 +++++++++++++++----- 1 file changed, 15 insertions(+), 5 deletions(-) diff --git a/fs/namespace.c b/fs/namespace.c index c58674a20cad..ad35f8c961ef 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -1537,23 +1537,33 @@ static struct mount *mnt_find_id_at_reverse(struct mnt_namespace *ns, u64 mnt_id static void *m_start(struct seq_file *m, loff_t *pos) { struct proc_mounts *p = m->private; + struct mount *mnt; down_read(&namespace_sem); - return mnt_find_id_at(p->ns, *pos); + mnt = mnt_find_id_at(p->ns, *pos); + if (mnt) + *pos = mnt->mnt_id_unique; + return mnt; } static void *m_next(struct seq_file *m, void *v, loff_t *pos) { - struct mount *next = NULL, *mnt = v; + struct mount *mnt = v; struct rb_node *node = rb_next(&mnt->mnt_node); - ++*pos; if (node) { - next = node_to_mount(node); + struct mount *next = node_to_mount(node); *pos = next->mnt_id_unique; + return next; } - return next; + + /* + * No more mounts. Set pos past current mount's ID so that if + * iteration restarts, mnt_find_id_at() returns NULL. + */ + *pos = mnt->mnt_id_unique + 1; + return NULL; } static void m_stop(struct seq_file *m, void *v) -- 2.47.3