From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 ADF3B1F8AC0; Tue, 3 Dec 2024 16:11:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733242275; cv=none; b=u31/Eei+Ugx4m56K944ig0sqjybc9INH/iZ+ss3bk1jVMiAESkcwK88StNKJClvsu4xZF72Gc/sewIKt76t/kfFgEcUPGolWvseBJqyhL4H5MDg0LbHo7A2GbCTg/xVQ+mqm4y/Bzmo3tXxwNkKofiSEnCgfb5GQUSp/dvN0WHU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733242275; c=relaxed/simple; bh=tfZXUnRpHBaFR9Na4YjOiz/uZoypBkVQZQP5KPkEW0c=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Iu4HnpjxjGbHZkTbaSJMMWt1ztKUJoJWOzdwjB8w3EJRZG0emo0vquuRxL9YtduG6IBMpYjmIVG07qUgpzRzQ2rPpBoIh1Dh9tjS/4Baf0QzLJv9XQoUjMc8OhVOzitd57wHZIZORhwa8O+M2HNenWwg/kSD6dvSSgFXnbKVEsU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=RStWqPO1; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="RStWqPO1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A5D88C4CEDE; Tue, 3 Dec 2024 16:11:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1733242275; bh=tfZXUnRpHBaFR9Na4YjOiz/uZoypBkVQZQP5KPkEW0c=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=RStWqPO19BBh7pUejtRFWJukF7kT73HB1j+fvbX7JkQxv2TJHPUxmDLgfZAREiShj XnD6TGTk62YKBd4IMkCTR5L6zT7V9VW/KOErPFu8NGPhY5lVq6uPEn6OT7zjrsvKrq 73dZwchMDyGPDyHJ413PDDFzzh/dRIvyAh8XshJ8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, stable@kernel.org, Jann Horn , Jan Kara Subject: [PATCH 6.12 659/826] fsnotify: Fix ordering of iput() and watched_objects decrement Date: Tue, 3 Dec 2024 15:46:26 +0100 Message-ID: <20241203144809.460050156@linuxfoundation.org> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20241203144743.428732212@linuxfoundation.org> References: <20241203144743.428732212@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org 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: Jann Horn commit 21d1b618b6b9da46c5116c640ac4b1cc8d40d63a upstream. Ensure the superblock is kept alive until we're done with iput(). Holding a reference to an inode is not allowed unless we ensure the superblock stays alive, which fsnotify does by keeping the watched_objects count elevated, so iput() must happen before the watched_objects decrement. This can lead to a UAF of something like sb->s_fs_info in tmpfs, but the UAF is hard to hit because race orderings that oops are more likely, thanks to the CHECK_DATA_CORRUPTION() block in generic_shutdown_super(). Also, ensure that fsnotify_put_sb_watched_objects() doesn't call fsnotify_sb_watched_objects() on a superblock that may have already been freed, which would cause a UAF read of sb->s_fsnotify_info. Cc: stable@kernel.org Fixes: d2f277e26f52 ("fsnotify: rename fsnotify_{get,put}_sb_connectors()") Signed-off-by: Jann Horn Signed-off-by: Jan Kara Signed-off-by: Greg Kroah-Hartman --- fs/notify/mark.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) --- a/fs/notify/mark.c +++ b/fs/notify/mark.c @@ -138,8 +138,11 @@ static void fsnotify_get_sb_watched_obje static void fsnotify_put_sb_watched_objects(struct super_block *sb) { - if (atomic_long_dec_and_test(fsnotify_sb_watched_objects(sb))) - wake_up_var(fsnotify_sb_watched_objects(sb)); + atomic_long_t *watched_objects = fsnotify_sb_watched_objects(sb); + + /* the superblock can go away after this decrement */ + if (atomic_long_dec_and_test(watched_objects)) + wake_up_var(watched_objects); } static void fsnotify_get_inode_ref(struct inode *inode) @@ -150,8 +153,11 @@ static void fsnotify_get_inode_ref(struc static void fsnotify_put_inode_ref(struct inode *inode) { - fsnotify_put_sb_watched_objects(inode->i_sb); + /* read ->i_sb before the inode can go away */ + struct super_block *sb = inode->i_sb; + iput(inode); + fsnotify_put_sb_watched_objects(sb); } /*