From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793881247; b=pDCSyFeHK3mQV2CWJhuVAP6ppenyVCh5ZTbaeqgr/wfmPFfiT6tUTdkaa99lomSruJFu n00jiix7/LXWyc7ORxL53+BgI4oBHDyM4wEfxdNGxKQx9pgrcfWWrQZZ0XAn+6E2YDba2 VwsUrJuPc5RGeRpOPM16+BskzQf3uqhJqmYn+0KrCes0yebmkTJOL0lbe9MJlXvqeKOXq SCgiMMMAa3st94EPSpJJjeYHR4+MI3pETJW0V4agKrL44qQhmNer6XoaaryAcI5YDt1Ts NQGpX+KG0U9ZG5bGbYUq5B/AtXoGPdJ6XHRtNa5A35M64k2B/uMAYufP/uYju+cpT5A== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793881247; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=2DqK50qOegGS2WP+VoAn0rftI92eyvVx/YD+jbbwuYo=; b=Z+KpF3OLsbUf+y1I+LHT5rVB8z61M4OkGBkIIxtG/ZcyVzRnIcsD9n8I8kNzfPdI1VU/ cGQ6j3uZjPtZ6oAThtrsx4Pfs0c4fpJwsRtBbsPiY+W/mZpRdarnzi0ZajfewJxwcfQG+ qsKJObnpHJBji/lpr5MV1MJn0/ccjhQE5bcieUDFsQhfgh/RfvkQQUB4XZKZB99dEidyK +5B1iVxyeqWbgibSWDReHolBbsUPjqG1GcKJEkN+dQ3JBiYQ4OTsgT/3F7KsVrA9qzgzB ZqC1l3wlaNNXnVKQ1rT1s+785QaZ+/egmEHsnobMV++0JLMZlPzOBVrtN8Ftw6v9SOQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b="LlA/DLDq"; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 36375606A31B for ; Thu, 5 Nov 2026 12:20:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=LlA/DLDq Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7BB821F000C1; Thu, 5 Nov 2026 12:20:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793881247; bh=2DqK50qOegGS2WP+VoAn0rftI92eyvVx/YD+jbbwuYo=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=LlA/DLDqVPT1I7o2bJB09mUtT2B6UnYhNg4pA/6pS0YPlSlGqGwoURPRpRTZnkzEc q8dvebbAOzg2PLeOrVn0QyxF2f2NIn4BcbMlB3xabl9nOohdohwcITPYaWWGtCLVRq B3seCOGdaZGeRO319mK8QqSWdJcmj0VX3m8lTX2MSVUfoPyLd3noBqrJUKycODHeKH v9yUJ8+x8Az3uhFZP6zJ4ohMqDfAlZZ/A5/og6HYe2DK1tDtk5Kr9WRms/mQRh3Q9D cXX7gPC729aOtvwvVOtsnSQLuLzrUrXTI6qPI8zWRo7/qJbKcGHm1Soevs4BEOzZ+T gGBNruyNpB7Zw== From: Sasha Levin To: stable@vger.kernel.org Cc: Chris Mason , Josef Bacik , Amir Goldstein , Sasha Levin Subject: [PATCH 5.15.y] ovl: hold a reference on the parent in readdir Date: Thu, 5 Nov 2026 07:20:45 -0500 Message-ID: <20261105121917.1276549-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026110448-rebuild-overpower-e0e1@gregkh> References: <2026110448-rebuild-overpower-e0e1@gregkh> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Chris Mason [ Upstream commit 16d319e12328acafeafd3eecdf09c46d7fb43452 ] Listing a directory on an overlay uses a freed dentry and crashes the kernel when a lookup moves the directory at the same time. Code that can sleep may only use d_parent without a reference while something stops a move of the dentry. ovl_iterate_real(), ovl_need_adjust_d_ino() and ovl_cache_update() use the d_parent of the listed directory and hold only the lock of that directory. When a lookup finds the directory under another parent after a change to a layer, d_splice_alias() moves it without that lock and drops its reference on the old parent. With a delay in ovl_iterate_real(), getdents64 on an overlay directory raced a rename in the lower layer and a lookup that moved its dentry, and after an rmdir of the old parent KASAN reported a use-after-free in security_inode_getattr(). Fix this by using dget_parent() in the three functions. Fixes: b5efccbe0a12 ("ovl: constant d_ino across copy up") Cc: stable@vger.kernel.org Signed-off-by: Chris Mason Signed-off-by: Josef Bacik [amir: fix comments in ovl_need_adjust_d_ino()] Signed-off-by: Amir Goldstein [ sashal: adapted ovl_need_adjust_d_ino() changes to the inline logic in ovl_iterate() ] Signed-off-by: Sasha Levin --- fs/overlayfs/readdir.c | 24 ++++++++++++++++++------ 1 file changed, 18 insertions(+), 6 deletions(-) diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c index 666cc62578f65..75e47ef3c7118 100644 --- a/fs/overlayfs/readdir.c +++ b/fs/overlayfs/readdir.c @@ -474,8 +474,8 @@ static int ovl_cache_update_ino(struct path *path, struct ovl_cache_entry *p) goto get; } if (p->len == 2 && p->name[1] == '.') { - /* we shall not be moved */ - this = dget(dir->d_parent); + /* d_splice_alias() can move even a locked dir */ + this = dget_parent(dir); goto get; } } @@ -693,6 +693,7 @@ static int ovl_iterate_real(struct file *file, struct dir_context *ctx) struct ovl_dir_file *od = file->private_data; struct dentry *dir = file->f_path.dentry; const struct ovl_layer *lower_layer = ovl_layer_lower(dir); + struct dentry *parent; struct ovl_readdir_translate rdt = { .ctx.actor = ovl_fill_real, .orig_ctx = ctx, @@ -703,18 +704,26 @@ static int ovl_iterate_real(struct file *file, struct dir_context *ctx) if (rdt.xinobits && lower_layer) rdt.fsid = lower_layer->fsid; - if (OVL_TYPE_MERGE(ovl_path_type(dir->d_parent))) { + /* + * The lock on dir does not stop d_splice_alias() from moving it to + * another parent, which drops the reference dir holds on this one. + */ + parent = dget_parent(dir); + if (OVL_TYPE_MERGE(ovl_path_type(parent))) { struct kstat stat; struct path statpath = file->f_path; - statpath.dentry = dir->d_parent; + statpath.dentry = parent; err = vfs_getattr(&statpath, &stat, STATX_INO, 0); - if (err) + if (err) { + dput(parent); return err; + } WARN_ON_ONCE(dir->d_sb->s_dev != stat.dev); rdt.parent_ino = stat.ino; } + dput(parent); if (ovl_is_impure_dir(file)) { rdt.cache = ovl_cache_get_impure(&file->f_path); @@ -742,6 +751,8 @@ static int ovl_iterate(struct file *file, struct dir_context *ctx) ovl_dir_reset(file); if (od->is_real) { + struct dentry *parent = dget_parent(dentry); + /* * If parent is merge, then need to adjust d_ino for '..', if * dir is impure then need to adjust d_ino for copied up @@ -750,11 +761,12 @@ static int ovl_iterate(struct file *file, struct dir_context *ctx) if (ovl_xino_bits(dentry->d_sb) || (ovl_same_fs(dentry->d_sb) && (ovl_is_impure_dir(file) || - OVL_TYPE_MERGE(ovl_path_type(dentry->d_parent))))) { + OVL_TYPE_MERGE(ovl_path_type(parent))))) { err = ovl_iterate_real(file, ctx); } else { err = iterate_dir(od->realfile, ctx); } + dput(parent); goto out; } -- 2.53.0