From 877d97f7e7b88c9cb8754bece152dc27a2a0f47a Mon Sep 17 00:00:00 2001
From: qihao <qihao_yewu@cmss.chinamobile.com>
Date: Mon, 16 Oct 2023 10:22:03 +0800
Subject: [PATCH] qga: Fix memory leak when output stream is unused

cheery-pick from d6f67b83b81bf49b5c62e77143ed39c020e51830

If capture-output is requested but one of the channels goes unused (eg.
we attempt to capture stderr but the command never writes to stderr), we
can leak memory.

guest_exec_output_watch() is (from what I understand) unconditionally
called for both streams if output capture is requested. The first call
will always pass the `p->size == p->length` check b/c both values are
0. Then GUEST_EXEC_IO_SIZE bytes will be allocated for the stream.

But when we reap the exited process there's a `gei->err.length > 0`
check to actually free the buffer. Which does not get run if the command
doesn't write to the stream.

Fix by making free() unconditional.

Reviewed-by: Konstantin Kostiuk <kkostiuk@redhat.com>
Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
Signed-off-by: Konstantin Kostiuk <kkostiuk@redhat.com>
Signed-off-by: qihao_yewu <qihao_yewu@cmss.chinamobile.com>
---
 qga/commands.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/qga/commands.c b/qga/commands.c
index 80501e4a73..05f89725be 100644
--- a/qga/commands.c
+++ b/qga/commands.c
@@ -210,16 +210,16 @@ GuestExecStatus *qmp_guest_exec_status(int64_t pid, Error **errp)
         if (gei->out.length > 0) {
             ges->has_out_data = true;
             ges->out_data = g_base64_encode(gei->out.data, gei->out.length);
-            g_free(gei->out.data);
             ges->has_out_truncated = gei->out.truncated;
         }
+        g_free(gei->out.data);
 
         if (gei->err.length > 0) {
             ges->has_err_data = true;
             ges->err_data = g_base64_encode(gei->err.data, gei->err.length);
-            g_free(gei->err.data);
             ges->has_err_truncated = gei->err.truncated;
         }
+        g_free(gei->err.data);
 
         QTAILQ_REMOVE(&guest_exec_state.processes, gei, next);
         g_free(gei);
-- 
2.41.0.windows.1