From: Willy Tarreau w@1wt.eu
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@gmail.com Suggested-by: Linus Torvalds torvalds@linuxfoundation.org Tested-by: Denis Efremov efremov@linux.com Signed-off-by: Willy Tarreau w@1wt.eu Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Denis Efremov efremov@linux.com --- drivers/block/floppy.c | 20 +++++++++----------- 1 file changed, 9 insertions(+), 11 deletions(-)
diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c index f24e3791e840..e133ff5fa596 100644 --- a/drivers/block/floppy.c +++ b/drivers/block/floppy.c @@ -521,8 +521,8 @@ 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; @@ -542,7 +542,6 @@ 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); @@ -1435,7 +1434,7 @@ 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) @@ -2055,7 +2054,7 @@ 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); @@ -2200,9 +2199,8 @@ 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; @@ -2677,7 +2675,7 @@ 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); @@ -2801,10 +2799,11 @@ 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; }
static void redo_fd_request(void) @@ -2860,7 +2859,6 @@ static void redo_fd_request(void) _floppy = floppy_type + DP->autodetect[DRS->probed_format]; } else probing = 0; - errors = &(current_req->error_count); tmp = make_raw_rw_request(); if (tmp < 2) { request_done(tmp);