From 77f55eac6c433e23e82a1b88b2d74f385c4c7d82 Mon Sep 17 00:00:00 2001
From: Prasad J Pandit <pjp@fedoraproject.org>
Date: Tue, 26 May 2020 16:47:43 +0530
Subject: exec: set map length to zero when returning NULL
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When mapping physical memory into host's virtual address space,
'address_space_map' may return NULL if BounceBuffer is in_use.
Set and return '*plen = 0' to avoid later NULL pointer dereference.

Reported-by: Alexander Bulekov <alxndr@bu.edu>
Fixes: https://bugs.launchpad.net/qemu/+bug/1878259
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Suggested-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
Message-Id: <20200526111743.428367-1-ppandit@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 exec.c | 1 +
 1 file changed, 1 insertion(+)

(limited to 'exec.c')

diff --git a/exec.c b/exec.c
index 9cbde85d8c..778263f1c6 100644
--- a/exec.c
+++ b/exec.c
@@ -3540,6 +3540,7 @@ void *address_space_map(AddressSpace *as,
 
     if (!memory_access_is_direct(mr, is_write)) {
         if (atomic_xchg(&bounce.in_use, true)) {
+            *plen = 0;
             return NULL;
         }
         /* Avoid unbounded allocations */
-- 
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