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 4EE4A157A4F; Tue, 23 Jul 2024 18:26:27 +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=1721759187; cv=none; b=mEnyGNnv1EQK4wbNxmgNzvxojQ6JoLkfe0mhUP3fML+4OxyMlXm5D68ISW+FxGWELOBwNuzSfLwlrR9ME0y2y50apalEGTdGikJ4nT5PQ2FdD4h5FBULXtPp5uAO1GfvraQUhsqJCPVNK+VrVNgiHGp6AQj7GuxNG9WbvVGqLII= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721759187; c=relaxed/simple; bh=XoxLOClTQ+dgc3yZLAvWJ9d+71pOnVt8mqD9ep6YE58=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=KDFy7Sn6T+aeshLQrpd5XVzGXHY664KWofO5D+PHHCLMUAzzwP8myxAjFl1lSHysYnJca4Dy9sI1p99bDyOc+1NnizYgTwTdczawdYt3Exyh3s+bQIwiIRdEsZjbMj0Udd79ztN8zOMtAMJMMoKAfv2/r1KM2p/rcF0LDKZqhD4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=nZ1+UaBY; 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="nZ1+UaBY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C7F99C4AF09; Tue, 23 Jul 2024 18:26:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1721759187; bh=XoxLOClTQ+dgc3yZLAvWJ9d+71pOnVt8mqD9ep6YE58=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=nZ1+UaBYMZnsgmvxUpOWfUQuyVvXFRHxAZQLCBkgqF3WUObQAj9zKUDXTj9Rc3mk2 vndLeTvUsSA6aEJOiCNrXDiypuVV9PVFlRxZA7b+VNJ26I9PxgYdiBey/AAxLTDX5z skrnpBuD+jsuR6BlnD12oCoczN9oozus0mrAXeYg= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, stable@kernel.org, Jann Horn , Jeff Layton , Christian Brauner Subject: [PATCH 6.1 009/105] filelock: Remove locks reliably when fcntl/close race is detected Date: Tue, 23 Jul 2024 20:22:46 +0200 Message-ID: <20240723180403.059233132@linuxfoundation.org> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20240723180402.490567226@linuxfoundation.org> References: <20240723180402.490567226@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 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jann Horn commit 3cad1bc010416c6dd780643476bc59ed742436b9 upstream. When fcntl_setlk() races with close(), it removes the created lock with do_lock_file_wait(). However, LSMs can allow the first do_lock_file_wait() that created the lock while denying the second do_lock_file_wait() that tries to remove the lock. In theory (but AFAIK not in practice), posix_lock_file() could also fail to remove a lock due to GFP_KERNEL allocation failure (when splitting a range in the middle). After the bug has been triggered, use-after-free reads will occur in lock_get_status() when userspace reads /proc/locks. This can likely be used to read arbitrary kernel memory, but can't corrupt kernel memory. This only affects systems with SELinux / Smack / AppArmor / BPF-LSM in enforcing mode and only works from some security contexts. Fix it by calling locks_remove_posix() instead, which is designed to reliably get rid of POSIX locks associated with the given file and files_struct and is also used by filp_flush(). Fixes: c293621bbf67 ("[PATCH] stale POSIX lock handling") Cc: stable@kernel.org Link: https://bugs.chromium.org/p/project-zero/issues/detail?id=2563 Signed-off-by: Jann Horn Link: https://lore.kernel.org/r/20240702-fs-lock-recover-2-v1-1-edd456f63789@google.com Reviewed-by: Jeff Layton Signed-off-by: Christian Brauner [stable fixup: ->c.flc_type was ->fl_type in older kernels] Signed-off-by: Jann Horn Signed-off-by: Greg Kroah-Hartman --- fs/locks.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) --- a/fs/locks.c +++ b/fs/locks.c @@ -2394,8 +2394,9 @@ int fcntl_setlk(unsigned int fd, struct error = do_lock_file_wait(filp, cmd, file_lock); /* - * Attempt to detect a close/fcntl race and recover by releasing the - * lock that was just acquired. There is no need to do that when we're + * Detect close/fcntl races and recover by zapping all POSIX locks + * associated with this file and our files_struct, just like on + * filp_flush(). There is no need to do that when we're * unlocking though, or for OFD locks. */ if (!error && file_lock->fl_type != F_UNLCK && @@ -2410,9 +2411,7 @@ int fcntl_setlk(unsigned int fd, struct f = files_lookup_fd_locked(files, fd); spin_unlock(&files->file_lock); if (f != filp) { - file_lock->fl_type = F_UNLCK; - error = do_lock_file_wait(filp, cmd, file_lock); - WARN_ON_ONCE(error); + locks_remove_posix(filp, files); error = -EBADF; } }