[PATCH v2] ui/console: fix three double frees in png_save()

[Volker Rümelin]

The png_destroy_write_struct() function frees all memory used by
libpng. Don't use the glib auto cleanup mechanism to free the
memory allocated by libpng again. For the pixman image, use only the
auto cleanup mechanism and remove the qemu_pixman_image_unref()
function call to prevent another double free.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1210
Fixes: 9a0a119a38 ("Added parameter to take screenshot with screendump as PNG")
Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>
---
v2:
There's no need to inititalize info_ptr with NULL. (Philippe)

 ui/console.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/ui/console.c b/ui/console.c
index 765892f84f..da179e1832 100644
--- a/ui/console.c
+++ b/ui/console.c
@@ -304,8 +304,8 @@ static bool png_save(int fd, pixman_image_t *image, Error 
**errp)
 {
     int width = pixman_image_get_width(image);
     int height = pixman_image_get_height(image);
-    g_autofree png_struct *png_ptr = NULL;
-    g_autofree png_info *info_ptr = NULL;
+    png_struct *png_ptr;
+    png_info *info_ptr;
     g_autoptr(pixman_image_t) linebuf =
                             qemu_pixman_linebuf_create(PIXMAN_a8r8g8b8, width);
     uint8_t *buf = (uint8_t *)pixman_image_get_data(linebuf);
@@ -346,7 +346,6 @@ static bool png_save(int fd, pixman_image_t *image, Error 
**errp)
         qemu_pixman_linebuf_fill(linebuf, image, width, 0, y);
         png_write_row(png_ptr, buf);
     }
-    qemu_pixman_image_unref(linebuf);
 
     png_write_end(png_ptr, NULL);
 
-- 
2.35.3