• Aristeu Rozanski's avatar
    ide-io: set REQ_FAILED when drive is dead · b5e1a4e2
    Aristeu Rozanski authored
    
    
    Currently it's possible to ide-cd to set an incorrect blocksize by
    reading garbage if the drive is dead:
    
    ide_cd_probe()
     -> cdrom_read_toc()
         -> cdrom_read_capacity()
             -> cdrom_queue_packet_command()
                 -> ide_do_drive_cmd()
                     -> ide_do_request()
                         -> start_request()
    
    on start_request():
    
            /* bail early if we've exceeded max_failures */
            if (drive->max_failures && (drive->failures > drive->max_failures)) {
                    goto kill_rq;
            }
    (...)
    kill_rq:
            ide_kill_rq(drive, rq);
            return ide_stopped;
    
    ide_kill_rq() and the next calls won't set REQ_FAILED on rq->cmd_flags and thus
    cdrom_queue_packet_command() won't return an error. then:
    
            stat = cdrom_queue_packet_command(drive, &req);
            if (stat == 0) {
                    *capacity = 1 + be32_to_cpu(capbuf.lba);
                    *sectors_per_frame =
                            be32_to_cpu(capbuf.blocklen) >> SECTOR_BITS;
            }
    
    cdrom_read_capacity() ends believing capbuf is valid but in fact it's just
    uninitialized data. back to cdrom_read_toc():
    
            /* Try to get the total cdrom capacity and sector size. */
            stat = cdrom_read_capacity(drive, &toc->capacity, &sectors_per_frame,
                                       sense);
            if (stat)
                    toc->capacity = 0x1fffff;
    
            set_capacity(info->disk, toc->capacity * sectors_per_frame);
            /* Save a private copy of te TOC capacity for error handling */
            drive->probed_capacity = toc->capacity * sectors_per_frame;
    
            blk_queue_hardsect_size(drive->queue,
                                    sectors_per_frame << SECTOR_BITS);
    
    that will set drive->queue->hardsect_size to be the random value.
    hardsect_size is used to calculate inode->i_blkbits. later on, on a read
    path:
    
    void create_empty_buffers(struct page *page,
                            unsigned long blocksize, unsigned long b_state)
    {       
            struct buffer_head *bh, *head, *tail;
    
            head = alloc_page_buffers(page, blocksize, 1);
            bh = head;
            do {    
                    bh->b_state |= b_state;
                    tail = bh;
                    bh = bh->b_this_page;
            } while (bh);
            tail->b_this_page = head;
    
    alloc_page_buffers() will return NULL if blocksize > 4096. blocksize is
    calculed based on inode->i_blkbits. that will trigger a null
    dereference on create_empty_buffers().
    Signed-off-by: default avatarAristeu Rozanski <arozansk@redhat.com>
    Cc: Borislav Petkov <bbpetkov@yahoo.de>
    Signed-off-by: default avatarBartlomiej Zolnierkiewicz <bzolnier@gmail.com>
    b5e1a4e2