From 7cfcc79b0ab800959716738aff9419f53fc68c9c Mon Sep 17 00:00:00 2001 From: Thomas Huth Date: Mon, 25 Sep 2023 11:18:54 +0200 Subject: [PATCH] hw/scsi/scsi-disk: Disallow block sizes smaller than 512 [CVE-2023-42467] We are doing things like nb_sectors /= (s->qdev.blocksize / BDRV_SECTOR_SIZE); in the code here (e.g. in scsi_disk_emulate_mode_sense()), so if the blocksize is smaller than BDRV_SECTOR_SIZE (=512), this crashes with a division by 0 exception. Thus disallow block sizes of 256 bytes to avoid this situation. Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1813 CVE: 2023-42467 Signed-off-by: Thomas Huth Message-ID: <20230925091854.49198-1-thuth@redhat.com> Signed-off-by: Paolo Bonzini --- hw/scsi/scsi-disk.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c index e0d79c7966..477ee2bcd4 100644 --- a/hw/scsi/scsi-disk.c +++ b/hw/scsi/scsi-disk.c @@ -1628,9 +1628,10 @@ static void scsi_disk_emulate_mode_select(SCSIDiskReq *r, uint8_t *inbuf) * Since the existing code only checks/updates bits 8-15 of the block * size, restrict ourselves to the same requirement for now to ensure * that a block size set by a block descriptor and then read back by - * a subsequent SCSI command will be the same + * a subsequent SCSI command will be the same. Also disallow a block + * size of 256 since we cannot handle anything below BDRV_SECTOR_SIZE. */ - if (bs && !(bs & ~0xff00) && bs != s->qdev.blocksize) { + if (bs && !(bs & ~0xfe00) && bs != s->qdev.blocksize) { s->qdev.blocksize = bs; trace_scsi_disk_mode_select_set_blocksize(s->qdev.blocksize); } -- 2.11.0