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 C662E50B8A8; Wed, 30 Sep 2026 17:41:55 +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=1790790117; cv=none; b=YVt+uwe8ZQtS5TgC7yi+U2ym1x05vfp06hCcJUgirX7IzGYdBHNdqFTbWFt/LwbtRTBW7hKwyP+ciUsPvL0SI9vpaYA4II4ZU6fLxpoV5En0mSJJg2VJA6wiBx0Xz9Ig2CSWNRkW4pZy5Ua7UaxpLxnxNDgGouDf21yuXFdbL58= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790790117; c=relaxed/simple; bh=5CgpsjbL7IAleEMGVbWW/BYxghmV8rHlHIoAOMpmBKA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=afr9sXJteTCeJBojoTgASrA64XFRRUkr5/2nJ/sO6GYzyIYpP7aBArb7Zj81fBSuam8hviIgJPqTzgC+2rePsM+TQaoZ8JdLx/lH7Ut9PQwgg4q2BgzGGScBptecJOKzVyBT3mlvQAuaQCOFeAuWGiYyw6h7FmBqt9uVjxNBcMw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=HJT1bhxF; 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="HJT1bhxF" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2B8391F000FF; Wed, 30 Sep 2026 17:41:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790790115; bh=lozs/1ZNZTsJNfsfaLA/6XTw8EzHmmv1CHilJh5basQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=HJT1bhxFg3yQvMhM9CmtdEr2Fukd8pYOBOHg5Wsl+hN9Kr7Ecpx5RIa3823i9pR3T mhVTSiENnmnDN6g7m9LzIcF0siGGWwJCOGSTg9XxO7Jsm5PYff+3Ch8XrQOVvXp/tn QgoAMzk6Ht7kKKaAHADjgd17AGlPtsHH2w7gbU4Q= 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 , Sasha Levin Subject: [PATCH 6.12 715/877] configfs: unhash the dentry before dropping the item in rmdir Date: Wed, 30 Sep 2026 17:27:06 +0200 Message-ID: <20260930152430.115317258@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152414.738996857@linuxfoundation.org> References: <20260930152414.738996857@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 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Vasileios Almpanis [ Upstream commit f06c2d26d1999d37e93299db0ecead04ca7d0b9f ] 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 [ adapted the configfs_remove_dir() change to the older remove_dir() helper. ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- fs/configfs/dir.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) --- a/fs/configfs/dir.c +++ b/fs/configfs/dir.c @@ -395,8 +395,17 @@ static void remove_dir(struct dentry * d configfs_remove_dirent(d); - if (d_really_is_positive(d)) - simple_rmdir(d_inode(parent),d); + if (d_really_is_positive(d)) { + if (!simple_rmdir(d_inode(parent), d)) + /* + * 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));