This is a note to let you know that I've just added the patch titled floppy: use a statically allocated error counter to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: floppy-use-a-statically-allocated-error-counter.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From f71f01394f742fc4558b3f9f4c7ef4c4cf3b07c8 Mon Sep 17 00:00:00 2001 From: Willy Tarreau <w@xxxxxx> Date: Sun, 8 May 2022 11:37:07 +0200 Subject: floppy: use a statically allocated error counter From: Willy Tarreau <w@xxxxxx> commit f71f01394f742fc4558b3f9f4c7ef4c4cf3b07c8 upstream. 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 <yuanmingbuaa@xxxxxxxxx> Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxx> Tested-by: Denis Efremov <efremov@xxxxxxxxx> Signed-off-by: Willy Tarreau <w@xxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Denis Efremov <efremov@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/block/floppy.c | 19 +++++++++---------- 1 file changed, 9 insertions(+), 10 deletions(-) --- a/drivers/block/floppy.c +++ b/drivers/block/floppy.c @@ -516,8 +516,8 @@ 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; @@ -537,7 +537,6 @@ 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); @@ -1426,7 +1425,7 @@ static int interpret_errors(void) if (DP->flags & FTD_MSG) DPRINT("Over/Underrun - retrying\n"); bad = 0; - } else if (*errors >= DP->max_errors.reporting) { + } else if (floppy_errors >= DP->max_errors.reporting) { print_errors(); } if (ST2 & ST2_WC || ST2 & ST2_BC) @@ -2049,7 +2048,7 @@ static void bad_flp_intr(void) if (!next_valid_format()) return; } - err_count = ++(*errors); + err_count = ++floppy_errors; INFBOUND(DRWE->badness, err_count); if (err_count > DP->max_errors.abort) cont->done(0); @@ -2194,9 +2193,8 @@ static int do_format(int drive, struct f 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; @@ -2679,7 +2677,7 @@ static int make_raw_rw_request(void) */ if (!direct || (indirect * 2 > direct * 3 && - *errors < DP->max_errors.read_track && + floppy_errors < DP->max_errors.read_track && ((!probing || (DP->read_track & (1 << DRS->probed_format)))))) { max_size = blk_rq_sectors(current_req); @@ -2812,8 +2810,10 @@ static int set_next_request(void) fdc_queue = 0; if (q) { current_req = blk_fetch_request(q); - if (current_req) + if (current_req) { + floppy_errors = 0; break; + } } } while (fdc_queue != old_pos); @@ -2873,7 +2873,6 @@ do_request: _floppy = floppy_type + DP->autodetect[DRS->probed_format]; } else probing = 0; - errors = &(current_req->errors); tmp = make_raw_rw_request(); if (tmp < 2) { request_done(tmp); Patches currently in stable-queue which might be from w@xxxxxx are queue-4.9/floppy-use-a-statically-allocated-error-counter.patch