Hi,
On 5/8/22 13:37, Willy Tarreau wrote:
> 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>
Could you please take this patch (only this one) to the stable trees?
commit f71f01394f742fc4558b3f9f4c7ef4c4cf3b07c8 upstream.
The patch applies cleanly to 5.17, 5.15, 5.10 kernels.
I'll send a backport for 5.4 and older kernels.
Thanks,
Denis
> ---
> 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);
