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 056781F7554; Tue, 3 Dec 2024 15:26:14 +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=1733239574; cv=none; b=QBP2YCWJAQvROVCvc6S1khKrZevGU3T3jnKe7i1MJ6PWNkdb6omcamXiKNYtE3y2HT2nZFgiFxxNeMdESq1hvRwWnb2fpg9sRp2pOXOKOsiXsq/03SkCVnPqCjSdIFFVXdiyizPnWE9H2TKswIi5duTFX4CrcVndxaiRLv8ZqYY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733239574; c=relaxed/simple; bh=Ejfn6XHQ6tRp3l1uTpr3+2SVcEuNevR8WuBPj/6RSqw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=hm6Zp+Ej7Gn5nFbHO+g4dmmJFy3O3rvJgna6wCt965eE9QL+v3TXmKPEmsBLIjk6OWeVoPbZGz8FCUG+tICz/gHkKrl038slXonjRE2MTggmWjuM17aB53itBTZHhsT9I8jxmraoqAwyBHdlQZqNp/pm+bKrhBMSbkoxlfYHk/s= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=0N9u0ssv; 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="0N9u0ssv" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 830A7C4CECF; Tue, 3 Dec 2024 15:26:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1733239573; bh=Ejfn6XHQ6tRp3l1uTpr3+2SVcEuNevR8WuBPj/6RSqw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=0N9u0ssvHECVCfnDg102klcahs1K41rOSdYkQioFO9M+wgvMoDYQisVv6GdZWbUmO iw39pbcFg6uRB+eIqpYv/pmj7PAxqJloKpLaZ1ukYcmSM7+yBtMB38vtOJ1UwzHkEd hG3Nx+ywYzCZbj55oGnBUXMqEYeqU4zVB2O8peYQ= 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 6.11 661/817] fsnotify: Fix ordering of iput() and watched_objects decrement Date: Tue, 3 Dec 2024 15:43:53 +0100 Message-ID: <20241203144021.760655080@linuxfoundation.org> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20241203143955.605130076@linuxfoundation.org> References: <20241203143955.605130076@linuxfoundation.org> User-Agent: quilt/0.67 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 6.11-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(-) diff --git a/fs/notify/mark.c b/fs/notify/mark.c index c45b222cf9c1..4981439e6209 100644 --- a/fs/notify/mark.c +++ b/fs/notify/mark.c @@ -138,8 +138,11 @@ static void fsnotify_get_sb_watched_objects(struct super_block *sb) 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(struct inode *inode) 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); } /* -- 2.47.1