From patchwork Sun May 8 09:37:07 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Willy Tarreau X-Patchwork-Id: 12842312 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 585CEC4707E for ; Sun, 8 May 2022 09:49:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231545AbiEHJxg (ORCPT ); Sun, 8 May 2022 05:53:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60764 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244834AbiEHJlS (ORCPT ); Sun, 8 May 2022 05:41:18 -0400 Received: from 1wt.eu (wtarreau.pck.nerim.net [62.212.114.60]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id B4BD1DEC0; Sun, 8 May 2022 02:37:26 -0700 (PDT) Received: (from willy@localhost) by pcw.home.local (8.15.2/8.15.2/Submit) id 2489bFex024590; Sun, 8 May 2022 11:37:15 +0200 From: Willy Tarreau To: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Denis Efremov , Geert Uytterhoeven , Christoph Hellwig , Minh Yuan , Linus Torvalds , Willy Tarreau Subject: [PATCH 1/3] floppy: use a statically allocated error counter Date: Sun, 8 May 2022 11:37:07 +0200 Message-Id: <20220508093709.24548-1-w@1wt.eu> X-Mailer: git-send-email 2.17.5 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Interrupt handler bad_flp_intr() may cause a UAF on the recently freed request just to increment the error count. There's no point keeping that one in the request anyway, and since the interrupt handler uses a static pointer to the error which cannot be kept in sync with the pending request, better make it use a static error counter that's reset for each new request. This reset now happens when entering redo_fd_request() for a new request via set_next_request(). One initial concern about a single error counter was that errors on one floppy drive could be reported on another one, but this problem is not real given that the driver uses a single drive at a time, as that PC-compatible controllers also have this limitation by using shared signals. As such the error count is always for the "current" drive. Reported-by: Minh Yuan Suggested-by: Linus Torvalds Tested-by: Denis Efremov Signed-off-by: Willy Tarreau Reviewed-by: Christoph Hellwig --- drivers/block/floppy.c | 18 ++++++++---------- 1 file changed, 8 insertions(+), 10 deletions(-) diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c index d5b9ff9bcbb2..015841f50f4e 100644 --- a/drivers/block/floppy.c +++ b/drivers/block/floppy.c @@ -509,8 +509,8 @@ static unsigned long fdc_busy; static DECLARE_WAIT_QUEUE_HEAD(fdc_wait); static DECLARE_WAIT_QUEUE_HEAD(command_done); -/* Errors during formatting are counted here. */ -static int format_errors; +/* errors encountered on the current (or last) request */ +static int floppy_errors; /* Format request descriptor. */ static struct format_descr format_req; @@ -530,7 +530,6 @@ static struct format_descr format_req; static char *floppy_track_buffer; static int max_buffer_sectors; -static int *errors; typedef void (*done_f)(int); static const struct cont_t { void (*interrupt)(void); @@ -1455,7 +1454,7 @@ static int interpret_errors(void) if (drive_params[current_drive].flags & FTD_MSG) DPRINT("Over/Underrun - retrying\n"); bad = 0; - } else if (*errors >= drive_params[current_drive].max_errors.reporting) { + } else if (floppy_errors >= drive_params[current_drive].max_errors.reporting) { print_errors(); } if (reply_buffer[ST2] & ST2_WC || reply_buffer[ST2] & ST2_BC) @@ -2095,7 +2094,7 @@ static void bad_flp_intr(void) if (!next_valid_format(current_drive)) return; } - err_count = ++(*errors); + err_count = ++floppy_errors; INFBOUND(write_errors[current_drive].badness, err_count); if (err_count > drive_params[current_drive].max_errors.abort) cont->done(0); @@ -2241,9 +2240,8 @@ static int do_format(int drive, struct format_descr *tmp_format_req) return -EINVAL; } format_req = *tmp_format_req; - format_errors = 0; cont = &format_cont; - errors = &format_errors; + floppy_errors = 0; ret = wait_til_done(redo_format, true); if (ret == -EINTR) return -EINTR; @@ -2759,10 +2757,11 @@ static int set_next_request(void) current_req = list_first_entry_or_null(&floppy_reqs, struct request, queuelist); if (current_req) { - current_req->error_count = 0; + floppy_errors = 0; list_del_init(¤t_req->queuelist); + return 1; } - return current_req != NULL; + return 0; } /* Starts or continues processing request. Will automatically unlock the @@ -2821,7 +2820,6 @@ static void redo_fd_request(void) _floppy = floppy_type + drive_params[current_drive].autodetect[drive_state[current_drive].probed_format]; } else probing = 0; - errors = &(current_req->error_count); tmp = make_raw_rw_request(); if (tmp < 2) { request_done(tmp);