From 62dae36be7a62348fa0ac191f248317c2dd885a0 Mon Sep 17 00:00:00 2001 From: Souvik Banerjee Date: Mon, 27 Jul 2026 09:31:39 -0400 Subject: [PATCH] ovl: use linked upper dentry in copy-up tmpfile MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit [ Upstream commit e348eecd4d8fa8d18a5157ff59f7be1dc59c5928 ] ovl_copy_up_tmpfile() stores the disconnected O_TMPFILE dentry as the overlay's upper dentry reference via ovl_inode_update(). vfs_tmpfile() allocated this dentry via d_alloc(parentpath->dentry, &slash_name), so d_name is "/" and d_parent is c->workdir. Local upper filesystems (ext4, btrfs, xfs, ...) immediately rename it to "#" via d_mark_tmpfile() inside their ->tmpfile() op; FUSE and virtiofs do not, so both fields stay that way. Neither identifies the destination directory and filename where ovl_do_link() actually linked the file. When the upper filesystem implements ->d_revalidate() (e.g. FUSE or virtiofs), ovl_revalidate_real() calls it with the dentry's parent inode and a snapshot of d_name. The server tries to look up "/" inside c->workdir, fails, and overlayfs reports -ESTALE. This causes persistent ESTALE errors for any file that was copied up via the tmpfile path, breaking dpkg, apt, and other tools that do rename-over-existing on overlayfs with a FUSE/virtiofs upper. Before commit 6b52243f633e ("ovl: fold copy-up helpers into callers"), the tmpfile copy-up path used a dedicated helper ovl_link_tmpfile() that captured the linked destination dentry returned by ovl_do_link(): err = ovl_do_link(temp, udir, upper); ... if (!err) *newdentry = dget(upper); and published it via ovl_inode_update(d_inode(c->dentry), newdentry). The fold inlined ovl_do_link() into ovl_copy_up_tmpfile() but dropped the dget(upper) capture, and rewrote the publish line as ovl_inode_update(d_inode(c->dentry), dget(temp)) — where temp is the disconnected O_TMPFILE dentry. Fix by keeping a reference to the linked destination dentry after ovl_do_link() succeeds, and publishing that dentry at the existing ovl_inode_update() call site. The non-tmpfile/workdir path continues to publish the renamed temporary dentry. Reproducer: - Mount overlayfs with virtiofs (or a FUSE fs whose server advertises FUSE_TMPFILE) as upper - Run: dpkg -i - Observe: "error installing new file '...': Stale file handle" Fixes: 6b52243f633e ("ovl: fold copy-up helpers into callers") Cc: stable@vger.kernel.org # v4.20+ Signed-off-by: Souvik Banerjee Link: https://patch.msgid.link/20260501232735.2610824-1-souvik@amlalabs.com Reviewed-by: Amir Goldstein Reviewed-by: Miklos Szeredi Signed-off-by: Christian Brauner (Amutable) [ adapted scoped credential and creation helpers to explicit credential, locking, lookup, and cleanup handling ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- fs/overlayfs/copy_up.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c index 97f373fd9879..89317e1e7361 100644 --- a/fs/overlayfs/copy_up.c +++ b/fs/overlayfs/copy_up.c @@ -864,7 +864,7 @@ static int ovl_copy_up_tmpfile(struct ovl_copy_up_ctx *c) { struct ovl_fs *ofs = OVL_FS(c->dentry->d_sb); struct inode *udir = d_inode(c->destdir); - struct dentry *temp, *upper; + struct dentry *temp, *upper, *newdentry = NULL; struct file *tmpfile; struct ovl_cu_creds cc; int err; @@ -901,6 +901,14 @@ static int ovl_copy_up_tmpfile(struct ovl_copy_up_ctx *c) err = PTR_ERR(upper); if (!IS_ERR(upper)) { err = ovl_do_link(ofs, temp, udir, upper); + if (!err) { + /* + * Record the linked dentry -- not the disconnected + * O_TMPFILE dentry -- so that ->d_revalidate() on + * the upper fs sees the real parent/name. + */ + newdentry = dget(upper); + } dput(upper); } inode_unlock(udir); @@ -916,7 +924,7 @@ static int ovl_copy_up_tmpfile(struct ovl_copy_up_ctx *c) if (!c->metacopy) ovl_set_upperdata(d_inode(c->dentry)); - ovl_inode_update(d_inode(c->dentry), dget(temp)); + ovl_inode_update(d_inode(c->dentry), newdentry); out: ovl_end_write(c->dentry);