From 1de58326994b0045ccfb28017d05fc1ddecdb92d Mon Sep 17 00:00:00 2001 From: Glenn Washburn Date: Fri, 11 Aug 2023 16:30:04 -0500 Subject: commands/videoinfo: Prevent crash when run while video driver already active The videoinfo command will initialize all non-active video adapters. Video drivers tend to zero out the global framebuffer object on initialization. This is not a problem when there is no active video adapter. However, when there is, then outputting to the video adapter will cause a crash because methods in the framebuffer object are reinitialized. For example, this command sequence will cause a crash. terminal_output --append gfxterm; videoinfo When running in a QEMU headless with GRUB built for the x86_64-efi target, the first command initializes the Bochs video adapter, which, among other things, sets the set_page() member function. Then when videoinfo is run, all non-Bochs video adapters will be initialized, each one wiping the framebuffer and thus setting set_page to NULL. Soon after the videoinfo command finishes there will be a call to grub_refresh(), which will ultimately call the framebuffer's set_page which will be NULL and cause a crash when called. Signed-off-by: Glenn Washburn Reviewed-by: Daniel Kiper --- grub-core/commands/videoinfo.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/grub-core/commands/videoinfo.c b/grub-core/commands/videoinfo.c index 5eb9697..205ba78 100644 --- a/grub-core/commands/videoinfo.c +++ b/grub-core/commands/videoinfo.c @@ -191,6 +191,11 @@ grub_cmd_videoinfo (grub_command_t cmd __attribute__ ((unused)), /* Don't worry about errors. */ grub_errno = GRUB_ERR_NONE; } + else if (id != GRUB_VIDEO_DRIVER_NONE) + { + grub_puts_ (N_(" A video driver is active, cannot initialize this driver until it is deactivated\n")); + continue; + } else { if (adapter->init ()) -- cgit v1.1