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From 1de58326994b0045ccfb28017d05fc1ddecdb92d Mon Sep 17 00:00:00 2001
From: Glenn Washburn <development@efficientek.com>
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 <development@efficientek.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
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 ())
--
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