esp: don't underflow cmdfifo in do_cmd()
authorMark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Wed, 7 Apr 2021 19:57:56 +0000 (20:57 +0100)
committerMark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Mon, 12 Apr 2021 21:35:53 +0000 (22:35 +0100)
commitfa7505c154d4d00ad89a747be2eda556643ce00e
tree3df77c250ec9c40a1eaa1bfedfc5c1c0d8be6ecc
parent99545751734035b76bd372c4e7215bb337428d89
esp: don't underflow cmdfifo in do_cmd()

If the guest tries to execute a CDB when cmdfifo is not empty before the start
of the message out phase then clearing the message out phase data will cause
cmdfifo to underflow due to cmdfifo_cdb_offset being larger than the amount of
data within.

Since this can only occur by issuing deliberately incorrect instruction
sequences, ensure that the maximum length of esp_fifo_pop_buf() is limited to
the size of the data within cmdfifo.

Buglink: https://bugs.launchpad.net/qemu/+bug/1909247
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Tested-by: Alexander Bulekov <alxndr@bu.edu>
Message-Id: <20210407195801.685-8-mark.cave-ayland@ilande.co.uk>
hw/scsi/esp.c