[PATCH] scsi/lsi53c895a: fix use-after-free in lsi_do_msgout (CVE-2022-0216)

[Mauro Matteo Cascella]

Set current_req->req to NULL to prevent reusing a free'd buffer in case of
repeated SCSI cancel requests. Thanks to Thomas Huth for suggesting the patch.

Fixes: CVE-2022-0216
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/972
Signed-off-by: Mauro Matteo Cascella <mcascell@redhat.com>
---
 hw/scsi/lsi53c895a.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/hw/scsi/lsi53c895a.c b/hw/scsi/lsi53c895a.c
index c8773f73f7..99ea42d49b 100644
--- a/hw/scsi/lsi53c895a.c
+++ b/hw/scsi/lsi53c895a.c
@@ -1028,8 +1028,9 @@ static void lsi_do_msgout(LSIState *s)
         case 0x0d:
             /* The ABORT TAG message clears the current I/O process only. */
             trace_lsi_do_msgout_abort(current_tag);
-            if (current_req) {
+            if (current_req && current_req->req) {
                 scsi_req_cancel(current_req->req);
+                current_req->req = NULL;
             }
             lsi_disconnect(s);
             break;
-- 
2.35.3