[PATCH-for-5.0] qga-posix: Avoid crashing process when failing to allocate memory

[Philippe Mathieu-Daudé]

Similarly to commit 807e2b6fce0 for Windows, kindly return a
QMP error message instead of crashing the whole process.

Cc: address@hidden
Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1594054
Reported-by: Fakhri Zulkifli <address@hidden>
Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
---
 qga/commands-posix.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/qga/commands-posix.c b/qga/commands-posix.c
index 93474ff770..8f127788e6 100644
--- a/qga/commands-posix.c
+++ b/qga/commands-posix.c
@@ -493,7 +493,13 @@ struct GuestFileRead *qmp_guest_file_read(int64_t handle, 
bool has_count,
         gfh->state = RW_STATE_NEW;
     }
 
-    buf = g_malloc0(count+1);
+    buf = g_try_malloc0(count + 1);
+    if (!buf) {
+        error_setg(errp,
+                   "failed to allocate sufficient memory "
+                   "to complete the requested service");
+        return NULL;
+    }
     read_count = fread(buf, 1, count, fh);
     if (ferror(fh)) {
         error_setg_errno(errp, errno, "failed to read file");
-- 
2.21.1