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commands/videoinfo: Prevent crash when run while video driver already active

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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>
This commit is contained in:
Glenn Washburn 2023-08-11 16:30:04 -05:00 committed by Daniel Kiper
parent 43bf0b2a10
commit 1de5832699
1 changed files with 5 additions and 0 deletions
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5
grub-core/commands/videoinfo.c
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@ -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 ())