From f71f01394f742fc4558b3f9f4c7ef4c4cf3b07c8 Mon Sep 17 00:00:00 2001 From: Willy Tarreau Date: Sun, 8 May 2022 11:37:07 +0200 Subject: [PATCH] floppy: use a statically allocated error counter 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 Signed-off-by: Linus Torvalds --- 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 @@ do_request: _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); -- 2.20.1