[PULL,08/30] exec: Fix bounce buffer allocation in address_space_map()

Submitted by Kevin Wolf on Oct. 31, 2013, 3:48 p.m.

Details

Message ID 1383234524-372-9-git-send-email-kwolf@redhat.com
State New
Headers show

Commit Message

Kevin Wolf Oct. 31, 2013, 3:48 p.m.
This fixes a regression introduced by commit e3127ae0c, which kept the
allocation size of the bounce buffer limited to one page in order to
avoid unbounded allocations (as explained in the commit message of
6d16c2f88), but broke the reporting of the shortened bounce buffer to
the caller. The caller therefore assumes that the full requested size
was provided and causes memory corruption when writing beyond the end of
the actually allocated buffer.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 exec.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

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diff --git a/exec.c b/exec.c
index 2e31ffc..b453713 100644
--- a/exec.c
+++ b/exec.c
@@ -2099,7 +2099,9 @@  void *address_space_map(AddressSpace *as,
         if (bounce.buffer) {
             return NULL;
         }
-        bounce.buffer = qemu_memalign(TARGET_PAGE_SIZE, TARGET_PAGE_SIZE);
+        /* Avoid unbounded allocations */
+        l = MIN(l, TARGET_PAGE_SIZE);
+        bounce.buffer = qemu_memalign(TARGET_PAGE_SIZE, l);
         bounce.addr = addr;
         bounce.len = l;