Re: [PATCH] fbdev: atyfb: fix array overflow
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From: Geert Uytterhoeven <geert@linux-m68k.org>
Date: 2016-06-23 08:50:09
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Hi Arnd, On Wed, Jun 22, 2016 at 2:37 PM, Arnd Bergmann [off-list ref] wrote:
quoted hunk ↗ jump to hunk
When building with CONFIG_UBSAN_SANITIZE_ALL on ARM, I get this gcc warning for atyfb: drivers/video/fbdev/aty/atyfb_base.c: In function 'aty_bl_update_status': drivers/video/fbdev/aty/atyfb_base.c:167:33: warning: array subscript is above array bounds [-Warray-bounds] drivers/video/fbdev/aty/atyfb_base.c:152:26: warning: array subscript is above array bounds [-Warray-bounds] Apparently the warning is correct and there is indeed an overflow, which was never caught. I could only reproduce this on ARM and have opened a bug against the compiler for the lack of warning. This patch makes the array larger, so we cover all possible registers in the LCD controller without an overflow. Signed-off-by: Arnd Bergmann <arnd@arndb.de> Link: https://bugs.linaro.org/show_bug.cgi?id#49 --- drivers/video/fbdev/aty/atyfb_base.c | 2 +- include/video/mach64.h | 1 + 2 files changed, 2 insertions(+), 1 deletion(-)diff --git a/drivers/video/fbdev/aty/atyfb_base.c b/drivers/video/fbdev/aty/atyfb_base.c index 001d3d871800..36ffba152eab 100644 --- a/drivers/video/fbdev/aty/atyfb_base.c +++ b/drivers/video/fbdev/aty/atyfb_base.c@@ -134,7 +134,7 @@ #if defined(CONFIG_PM) || defined(CONFIG_PMAC_BACKLIGHT) || \ defined (CONFIG_FB_ATY_GENERIC_LCD) || defined(CONFIG_FB_ATY_BACKLIGHT) -static const u32 lt_lcd_regs[] = { +static const u32 lt_lcd_regs[LCD_REG_NUM] = { CNFG_PANEL_LG, LCD_GEN_CNTL_LG, DSTN_CONTROL_LG,diff --git a/include/video/mach64.h b/include/video/mach64.h index 89e91c0cb737..9f74e9e0aeb8 100644 --- a/include/video/mach64.h +++ b/include/video/mach64.h@@ -1299,6 +1299,7 @@ #define APC_LUT_KL 0x38 #define APC_LUT_MN 0x39 #define APC_LUT_OP 0x3A +#define LCD_REG_NUM 0x3B /* total number */ /* Values in LCD_GEN_CTRL */ #define CRT_ON 0x00000001ul
This doesn't look like the right fix to me.
Before, aty_st_lcd(LCD_MISC_CNTL, reg, par) in aty_bl_update_status()
wrote into an arbitrary register.
With your fix, it will write to register 0, which is IMHO also not OK.
I think aty_st_lcd() and aty_ld_lcd() should check whether the index is
out of range, perhaps even with a WARN_ON()?
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