Re: [PATCH] video/logo: prevent use of logos after they have been freed
From: Geert Uytterhoeven <geert@linux-m68k.org>
Date: 2014-12-18 13:46:10
Also in:
linux-arm-kernel, lkml
Hi Tomi, On Thu, Dec 18, 2014 at 12:57 PM, Tomi Valkeinen [off-list ref] wrote:
quoted hunk ↗ jump to hunk
If the probe of an fb driver has been deferred due to missing dependencies, and the probe is later ran when a module is loaded, the fbdev framework will try to find a logo to use. However, the logos are __initdata, and have already been freed. This causes sometimes page faults, if the logo memory is not mapped, sometimes other random crashes as the logo data is invalid, and sometimes nothing, if the fbdev decides to reject the logo (e.g. the random value depicting the logo's height is too big). This patch adds a late_initcall function to mark the logos as freed. In reality the logos are freed later, and fbdev probe may be ran between this late_initcall and the freeing of the logos. In that case we will miss drawing the logo, even if it would be possible. Signed-off-by: Tomi Valkeinen <redacted> --- drivers/video/logo/logo.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-)diff --git a/drivers/video/logo/logo.c b/drivers/video/logo/logo.c index 940cd196eef5..10fbfd8ab963 100644 --- a/drivers/video/logo/logo.c +++ b/drivers/video/logo/logo.c@@ -21,6 +21,21 @@ static bool nologo; module_param(nologo, bool, 0); MODULE_PARM_DESC(nologo, "Disables startup logo"); +/* + * Logos are located in the initdata, and will be freed in kernel_init. + * Use late_init to mark the logos as freed to prevent any further use. + */ + +static bool logos_freed; + +static int __init fb_logo_late_init(void) +{ + logos_freed = true;
Just set nologo to true?
+ return 0; +} + +late_initcall(fb_logo_late_init);
Hmm...
quoted hunk ↗ jump to hunk
+ /* logo's are marked __initdata. Use __init_refok to tell * modpost that it is intended that this function uses data * marked __initdata.@@ -29,7 +44,7 @@ const struct linux_logo * __init_refok fb_find_logo(int depth) { const struct linux_logo *logo = NULL; - if (nologo) + if (nologo || logos_freed)
A long time ago (ibefore 2.1.124), we used to have a test on initmem_freed
here. But that variable no longer exists.
Perhaps you can check system_state? That's variable is changed from
SYSTEM_BOOTING to SYSTEM_RUNNING in kernel_init(), after freeing
initmem.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds