From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0FDD84E3234; Thu, 17 Sep 2026 15:46:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789660022; cv=none; b=gt4QrojCKzRsS490s0HaDbyduKfMN7IJMS6poHWpDB+Ghvq4Jy4IZuasCvOimN2Z5MJo03ORv1wAfe5VKO2CnrN1XsiIOibQKzJV6JH25iItoY0KiLst9DjoVHTA3n0Wxa8sc27nZlY34ZpJ/RHFQSG/dfP1gjkm8hPQ1ibYjhQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789660022; c=relaxed/simple; bh=fFJ5uLYnKwJiUrczPoeJ8vpw+ldB+vg4RwkzJlD2bJw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=lPLj4X4a1eUig8rvqYTZ245rAtoAPjIesPjoGc0lTF6CSFqgY8Q7IG4wT5wAyvDSKqgjVFZom7YBMxN0bxYDo8cD5gxNsTdQ9mtIYj74gt/c4drSDTQ2RunwBI0X84bRPe3goAglE85ky/aHX9zZWsE32j8r/jbuZhM3tANiJoc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=IFUiL7g4; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="IFUiL7g4" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 601CB1F00893; Thu, 17 Sep 2026 15:46:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789660014; bh=fYidH0G//thNHXb8TOC4K36rdD/lRE1o5ib+cXwnty8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=IFUiL7g4pbcKGrFFJG52e7mv2yKDYeQeiHsW3uqnFqOPDoym7vf/x1kbgYchnfU3a FaxN2JGaKP/7tWBZ3Y4ThTSNmFnRc5Cs1IppE/nmXyGM9YhgCxO8bKuwLAT1AUCgbN ywGviazgKbZWFFt0jm+ZtAbJAiCx5i/5kR/rBEzo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+6b16e3d085833cbf3e25@syzkaller.appspotmail.com, Vasileios Almpanis , Breno Leitao Subject: [PATCH 7.2 449/733] configfs: unhash the dentry before dropping the item in rmdir Date: Thu, 17 Sep 2026 16:12:37 +0100 Message-ID: <20260917151403.086149123@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260917151350.597953846@linuxfoundation.org> References: <20260917151350.597953846@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 7.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Vasileios Almpanis commit f06c2d26d1999d37e93299db0ecead04ca7d0b9f upstream. configfs_get_config_item() treats a hashed dentry as proof that sd->s_element is a live config_item. configfs_rmdir() breaks that: simple_rmdir() leaves the dentry hashed, the last reference to the item is dropped right after, and the dentry is only unhashed by d_delete() once ->rmdir() has returned. configfs_symlink() resolves its target holding no lock on it, so get_target() can land in that window: BUG: KASAN: slab-use-after-free in config_item_get+0x26/0x90 get_target fs/configfs/symlink.c:128 [inline] configfs_symlink+0x4ab/0x1030 fs/configfs/symlink.c:185 Unhash in configfs_remove_dir(), while the item is still guaranteed to be there. A reference obtained just before that stays harmless, as create_link() rechecks CONFIGFS_USET_DROPPING, already set by configfs_detach_prep(). Both configfs_unregister_subsystem() paths d_drop() after detaching, so this only makes rmdir match them. Reported-by: syzbot+6b16e3d085833cbf3e25@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=6b16e3d085833cbf3e25 Fixes: 7063fbf22611 ("[PATCH] configfs: User-driven configuration filesystem") Cc: stable@vger.kernel.org Signed-off-by: Vasileios Almpanis Tested-by: Breno Leitao Reviewed-by: Breno Leitao Link: https://patch.msgid.link/20260730093435.195441-3-vasilisalmpanis@gmail.com Signed-off-by: Breno Leitao Signed-off-by: Greg Kroah-Hartman --- fs/configfs/dir.c | 9 +++++++++ 1 file changed, 9 insertions(+) --- a/fs/configfs/dir.c +++ b/fs/configfs/dir.c @@ -416,6 +416,15 @@ static void configfs_remove_dir(struct d if (d_really_is_positive(d)) { if (unlikely(simple_rmdir(d_inode(parent), d))) pr_warn("remove_dir (%pd): attributes remain", d); + else + /* + * configfs_get_config_item() takes a hashed dentry as + * proof that ->s_element is still alive. Our caller + * is about to drop the last reference to the item and + * the VFS will not unhash until after we return, so + * unhash it here. + */ + d_drop(d); } pr_debug(" o %pd removing done (%d)\n", d, d_count(d));