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, §ors_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: Aristeu Rozanski <arozansk@redhat.com>
Cc: Borislav Petkov <bbpetkov@yahoo.de>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
b5e1a4e286