From 31bfda8ca774523778ea5a3d11991c05545ba491 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Krzysztof=20Wilczy=C5=84ski?= Date: Sat, 13 Jun 2026 21:10:05 +0000 Subject: [PATCH] proc: only bump parent nlink when registering directories MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit commit 16b02eb4b9b272c221255c20d34ccd5db53a3ed3 upstream. proc_register() increments the parent directory's link count for every entry it registers, while remove_proc_entry() and remove_proc_subtree() decrement it only when the removed entry is a directory. Regular files thus inflate the parent's count while they exist, and leak one link permanently on every create and remove cycle. For example, /proc/bus/pci/00 with twenty-two device files and no subdirectories reports nlink 24 instead of 2, and SR-IOV VF enable and disable cycles, each creating and removing the VF config space entries under /proc/bus/pci/, inflate the link count of that directory without bound. Before commit e06689bf5701 ("proc: change ->nlink under proc_subdir_lock"), the increment lived in proc_mkdir_data() and proc_create_mount_point(), and was therefore applied only to directories. Moving it into proc_register() to bring it under proc_subdir_lock dropped the S_ISDIR check. Thus, move the nlink accounting into pde_subdir_insert() and pde_erase(), only updating it for directories in both, so the link count is always changed together with the directory entry itself. Fixes: e06689bf5701 ("proc: change ->nlink under proc_subdir_lock") Cc: stable@vger.kernel.org # v5.5+ Signed-off-by: Krzysztof Wilczyński Link: https://patch.msgid.link/20260613211005.921692-1-kwilczynski@kernel.org Signed-off-by: Christian Brauner (Amutable) Signed-off-by: Greg Kroah-Hartman --- fs/proc/generic.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/fs/proc/generic.c b/fs/proc/generic.c index 9eff57c7aef3..91c25a5f770c 100644 --- a/fs/proc/generic.c +++ b/fs/proc/generic.c @@ -112,6 +112,8 @@ static bool pde_subdir_insert(struct proc_dir_entry *dir, /* Add new node and rebalance tree. */ rb_link_node(&de->subdir_node, parent, new); rb_insert_color(&de->subdir_node, root); + if (S_ISDIR(de->mode)) + dir->nlink++; return true; } @@ -399,7 +401,6 @@ struct proc_dir_entry *proc_register(struct proc_dir_entry *dir, write_unlock(&proc_subdir_lock); goto out_free_inum; } - dir->nlink++; write_unlock(&proc_subdir_lock); return dp; @@ -698,6 +699,8 @@ static void pde_erase(struct proc_dir_entry *pde, struct proc_dir_entry *parent) { rb_erase(&pde->subdir_node, &parent->subdir); RB_CLEAR_NODE(&pde->subdir_node); + if (S_ISDIR(pde->mode)) + parent->nlink--; } /* @@ -723,8 +726,6 @@ void remove_proc_entry(const char *name, struct proc_dir_entry *parent) de = NULL; } else { pde_erase(de, parent); - if (S_ISDIR(de->mode)) - parent->nlink--; } } write_unlock(&proc_subdir_lock); @@ -783,8 +784,6 @@ int remove_proc_subtree(const char *name, struct proc_dir_entry *parent) continue; } next = de->parent; - if (S_ISDIR(de->mode)) - next->nlink--; write_unlock(&proc_subdir_lock); proc_entry_rundown(de);