On Thu, Jun 23, 2016 at 11:22:20AM +0200, Arnd Bergmann wrote: > 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; We don't want to take the 'else' branch ever, so this isn't any safer than the original code. So maybe something like this: if (M64_HAS(LT_LCD_REGS)) { if (WARN_ON(index >= ARRAY_SIZE(lt_lcd_regs))) return; ... } else { ... } But aty_ld_lcd() still needs to return something even if the index is bogus. Either all ones or all zeroes I guess. Which one is better? I don't know. Not sure what the hardware gives you when trying to read an invalid register. > @@ -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 -- Ville Syrjälä syrjala@xxxxxx http://www.sci.fi/~syrjala/ -- 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
