On Thursday, June 23, 2016 10:50:04 AM CEST Geert Uytterhoeven wrote: > Hi Arnd, > > On Wed, Jun 22, 2016 at 2:37 PM, Arnd Bergmann <arnd@xxxxxxxx> wrote: > > 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@xxxxxxxx> > > Link: https://bugs.linaro.org/show_bug.cgi?id=2349 > > --- > > 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. Ok, I see now. I thought it array was for initializing the registers and caching the contents as some other drivers do it, but it's really used for some indirect addressing method. > I think aty_st_lcd() and aty_ld_lcd() should check whether the index is > out of range, perhaps even with a WARN_ON()? Just guessing what the right behavior would be, maybe something like this? That would assume that the LCD_MISC_CNTL is accessible through LCD_INDEX/LCD_DATA but not through a direct register. Arnd diff --git a/drivers/video/fbdev/aty/atyfb_base.c b/drivers/video/fbdev/aty/atyfb_base.c index 36ffba152eab..c67d4b767e9a 100644 --- a/drivers/video/fbdev/aty/atyfb_base.c +++ b/drivers/video/fbdev/aty/atyfb_base.c @@ -148,7 +148,7 @@ static const u32 lt_lcd_regs[LCD_REG_NUM] = { void aty_st_lcd(int index, u32 val, const struct atyfb_par *par) { - if (M64_HAS(LT_LCD_REGS)) { + if (M64_HAS(LT_LCD_REGS) && index < ARRAY_SIZE(lt_lcd_regs)) { aty_st_le32(lt_lcd_regs[index], val, par); } else { unsigned long temp; @@ -163,7 +163,7 @@ void aty_st_lcd(int index, u32 val, const struct atyfb_par *par) u32 aty_ld_lcd(int index, const struct atyfb_par *par) { - if (M64_HAS(LT_LCD_REGS)) { + if (M64_HAS(LT_LCD_REGS) && index < ARRAY_SIZE(lt_lcd_regs)) { return aty_ld_le32(lt_lcd_regs[index], par); } else { unsigned long temp; -- To unsubscribe from this list: send the line "unsubscribe linux-fbdev" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
