From 892af81380c9ba24a7c8582b5fae4d37a2e5cf47 Mon Sep 17 00:00:00 2001
From: Prasad J Pandit <pjp@fedoraproject.org>
Date: Tue, 23 Feb 2021 15:20:03 +0800
Subject: [PATCH] ide:atapi: check io_buffer_index in ide_atapi_cmd_reply_end

Fix CVE-2020-29443

During data transfer via packet command in 'ide_atapi_cmd_reply_end'
's->io_buffer_index' could exceed the 's->io_buffer' length, leading
to OOB access issue. Add check to avoid it.
 ...
 #9  ahci_pio_transfer ../hw/ide/ahci.c:1383
 #10 ide_transfer_start_norecurse ../hw/ide/core.c:553
 #11 ide_atapi_cmd_reply_end ../hw/ide/atapi.c:284
 #12 ide_atapi_cmd_read_pio ../hw/ide/atapi.c:329
 #13 ide_atapi_cmd_read ../hw/ide/atapi.c:442
 #14 cmd_read ../hw/ide/atapi.c:988
 #15 ide_atapi_cmd ../hw/ide/atapi.c:1352
 #16 ide_transfer_start ../hw/ide/core.c:561
 #17 cmd_packet ../hw/ide/core.c:1729
 #18 ide_exec_cmd ../hw/ide/core.c:2107
 #19 handle_reg_h2d_fis ../hw/ide/ahci.c:1267
 #20 handle_cmd ../hw/ide/ahci.c:1318
 #21 check_cmd ../hw/ide/ahci.c:592
 #22 ahci_port_write ../hw/ide/ahci.c:373
 #23 ahci_mem_write ../hw/ide/ahci.c:513

Reported-by: Wenxiang Qian <leonwxqian@gmail.com>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>

Signed-off-by: Jiajie Li <lijiajie11@huawei.com>
---
 hw/ide/atapi.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/hw/ide/atapi.c b/hw/ide/atapi.c
index 1b0f66cc08..fc9dc87f03 100644
--- a/hw/ide/atapi.c
+++ b/hw/ide/atapi.c
@@ -300,6 +300,9 @@ void ide_atapi_cmd_reply_end(IDEState *s)
         s->packet_transfer_size -= size;
         s->elementary_transfer_size -= size;
         s->io_buffer_index += size;
+	if (s->io_buffer_index > s->io_buffer_total_len) {
+            return;
+        }
 
         /* Some adapters process PIO data right away.  In that case, we need
          * to avoid mutual recursion between ide_transfer_start
-- 
2.27.0

