[PATCH 6.6 265/638] pstore: inode: Only d_invalidate() is needed

Sasha Levin
2024-03-24T23:05:37Z

From: Kees Cook <keescook@chromium.org>

[ Upstream commit a43e0fc5e9134a46515de2f2f8d4100b74e50de3 ]

Unloading a modular pstore backend with records in pstorefs would
trigger the dput() double-drop warning:

WARNING: CPU: 0 PID: 2569 at fs/dcache.c:762 dput.part.0+0x3f3/0x410

Using the combo of d_drop()/dput() (as mentioned in
Documentation/filesystems/vfs.rst) isn't the right approach here, and
leads to the reference counting problem seen above. Use d_invalidate()
and update the code to not bother checking for error codes that can
never happen.

Suggested-by: Alexander Viro <viro@zeniv.linux.org.uk>
Fixes: 609e28bb139e ("pstore: Remove filesystem records when backend is unregistered")
Signed-off-by: Kees Cook <keescook@chromium.org>
---
fs/pstore/inode.c | 10 +++-------
1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/fs/pstore/inode.c b/fs/pstore/inode.c
index 904863dbf5327..7dbbf3b6d98d3 100644
--- a/fs/pstore/inode.c
+++ b/fs/pstore/inode.c
@@ -306,7 +306,6 @@ int pstore_put_backend_records(struct pstore_info *psi)
{
struct pstore_private *pos, *tmp;
struct dentry *root;
- int rc = 0;

root = psinfo_lock_root();
if (!root)
@@ -316,11 +315,8 @@ int pstore_put_backend_records(struct pstore_info *psi)
list_for_each_entry_safe(pos, tmp, &records_list, list) {
if (pos->record->psi == psi) {
list_del_init(&pos->list);
- rc = simple_unlink(d_inode(root), pos->dentry);
- if (WARN_ON(rc))
- break;
- d_drop(pos->dentry);
- dput(pos->dentry);
+ d_invalidate(pos->dentry);
+ simple_unlink(d_inode(root), pos->dentry);
pos->dentry = NULL;
}
}
@@ -328,7 +324,7 @@ int pstore_put_backend_records(struct pstore_info *psi)

inode_unlock(d_inode(root));

- return rc;
+ return 0;
}

/*
--
2.43.0