MODE_PAGE_ALLS causes an off-by-one error in mode_sense_page() when accessing the stack-allocated mode_sense_valid buffer. MODE_PAGE_ALLS is only valid for MODE SENSE commands. Do not process it in MODE SELECT commands.
Fixes: CVE-2021-3930 RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=2020588 Signed-off-by: Mauro Matteo Cascella <mcasc...@redhat.com> Reported-by: Qiuhao Li <qiuhao...@outlook.com> --- hw/scsi/scsi-disk.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c index e8a547dbb7..5852e8dcfd 100644 --- a/hw/scsi/scsi-disk.c +++ b/hw/scsi/scsi-disk.c @@ -1087,6 +1087,7 @@ static int mode_sense_page(SCSIDiskState *s, int page, uint8_t **p_outbuf, uint8_t *p = *p_outbuf + 2; int length; + assert(page != MODE_PAGE_ALLS); if ((mode_sense_valid[page] & (1 << s->qdev.type)) == 0) { return -1; } @@ -1428,6 +1429,11 @@ static int scsi_disk_check_mode_select(SCSIDiskState *s, int page, return -1; } + /* MODE_PAGE_ALLS is only valid for MODE SENSE commands */ + if (page == MODE_PAGE_ALLS) { + return -1; + } + p = mode_current; memset(mode_current, 0, inlen + 2); len = mode_sense_page(s, page, &p, 0); -- 2.31.1
