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[PATCH v4] exec: set map length to zero when returning NULL
From: |
P J P |
Subject: |
[PATCH v4] exec: set map length to zero when returning NULL |
Date: |
Tue, 26 May 2020 16:47:43 +0530 |
From: Prasad J Pandit <address@hidden>
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 <address@hidden>
Fixes: https://bugs.launchpad.net/qemu/+bug/1878259
Suggested-by: Paolo Bonzini <address@hidden>
Suggested-by: Peter Maydell <address@hidden>
Signed-off-by: Prasad J Pandit <address@hidden>
---
exec.c | 1 +
include/exec/memory.h | 3 ++-
2 files changed, 3 insertions(+), 1 deletion(-)
Update v4: update address_space_map API doc text
-> https://lists.gnu.org/archive/html/qemu-devel/2020-05/msg07281.html
diff --git a/exec.c b/exec.c
index 5162f0d12f..4eea84bf66 100644
--- a/exec.c
+++ b/exec.c
@@ -3538,6 +3538,7 @@ 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 */
diff --git a/include/exec/memory.h b/include/exec/memory.h
index e000bd2f97..8fa2d3cab2 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -2303,7 +2303,8 @@ bool address_space_access_valid(AddressSpace *as, hwaddr
addr, hwaddr len,
/* address_space_map: map a physical memory region into a host virtual address
*
* May map a subset of the requested range, given by and returned in @plen.
- * May return %NULL if resources needed to perform the mapping are exhausted.
+ * May return %NULL and set *@plen to zero(0), if resources needed to perform
+ * the mapping are exhausted.
* Use only for reads OR writes - not for read-modify-write operations.
* Use cpu_register_map_client() to know when retrying the map operation is
* likely to succeed.
--
2.26.2
- [PATCH v4] exec: set map length to zero when returning NULL,
P J P <=