scsi-disk: fix overflow when block size is not a multiple of BDRV_SECTOR_SIZE

In scsi_disk_emulate_write_same() the number of host sectors to transfer is
calculated as (s->qdev.blocksize / BDRV_SECTOR_SIZE) which is then used to
copy data in block size chunks to the iov buffer.

Since the loop copying the data to the iov buffer uses a fixed increment of
s->qdev.blocksize then using a block size that isn't a multiple of
BDRV_SECTOR_SIZE introduces a rounding error in the iov buffer size calculation
such that the iov buffer copy overflows the space allocated.

Update the iov buffer copy for() loop so that it will use the smallest of either
the current block size or the remaining transfer count to prevent the overflow.

Signed-off-by: Mark Cave-Ayland <[email protected]>
Message-Id: <20220730122656[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>

diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c
index f5cdb9ad4b546de8f8f648f96c28b85d5d0f6cde..3027ac3b1ed6d4d452f0ea70f3cdb6107a851978 100644 (file)
--- a/hw/scsi/scsi-disk.c
+++ b/hw/scsi/scsi-disk.c
@@ -1849,7 +1849,7 @@ static void scsi_disk_emulate_write_same(SCSIDiskReq *r, uint8_t *inbuf)
     uint32_t nb_sectors = scsi_data_cdb_xfer(r->req.cmd.buf);
     WriteSameCBData *data;
     uint8_t *buf;
-    int i;
+    int i, l;
 
     /* Fail if PBDATA=1 or LBDATA=1 or ANCHOR=1.  */
     if (nb_sectors == 0 || (req->cmd.buf[1] & 0x16)) {
@@ -1891,8 +1891,9 @@ static void scsi_disk_emulate_write_same(SCSIDiskReq *r, uint8_t *inbuf)
                                               data->iov.iov_len);
     qemu_iovec_init_external(&data->qiov, &data->iov, 1);
 
-    for (i = 0; i < data->iov.iov_len; i += s->qdev.blocksize) {
-        memcpy(&buf[i], inbuf, s->qdev.blocksize);
+    for (i = 0; i < data->iov.iov_len; i += l) {
+        l = MIN(s->qdev.blocksize, data->iov.iov_len - i);
+        memcpy(&buf[i], inbuf, l);
     }
 
     scsi_req_ref(&r->req);