On Thu, May 23, 2024 at 08:00:07PM -0700, Andrew Morton wrote: > > The patch titled > Subject: gcc: disable '-Warray-bounds' for gcc-9 > has been added to the -mm mm-hotfixes-unstable branch. Its filename is > gcc-disable-warray-bounds-for-gcc-9.patch Hi Andrew, The script said you've applied it to mm-hotfixes, but the patch is still not in mainline. Are you going to move it in this cycle, or what are your plans on it? Thanks, Yury > This patch will shortly appear at > https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/gcc-disable-warray-bounds-for-gcc-9.patch > > This patch will later appear in the mm-hotfixes-unstable branch at > git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm > > Before you just go and hit "reply", please: > a) Consider who else should be cc'ed > b) Prefer to cc a suitable mailing list as well > c) Ideally: find the original patch on the mailing list and do a > reply-to-all to that, adding suitable additional cc's > > *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** > > The -mm tree is included into linux-next via the mm-everything > branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm > and is updated there every 2-3 working days > > ------------------------------------------------------ > From: Yury Norov <yury.norov@xxxxxxxxx> > Subject: gcc: disable '-Warray-bounds' for gcc-9 > Date: Wed, 22 May 2024 15:58:30 -0700 > > '-Warray-bounds' is already disabled for gcc-10+. Now that we've merged > bitmap_{read,write), I see the following error when building the kernel > with gcc-9.4 (Ubuntu 20.04.4 LTS) for x86_64 allmodconfig: > > drivers/pinctrl/pinctrl-cy8c95x0.c: In function `cy8c95x0_read_regs_mask.isra.0': > include/linux/bitmap.h:756:18: error: array subscript [1, 288230376151711744] is outside array bounds of `long unsigned int[1]' [-Werror=array-bounds] > 756 | value_high = map[index + 1] & BITMAP_LAST_WORD_MASK(start + nbits); > | ~~~^~~~~~~~~~~ > > The immediate reason is that the commit b44759705f7d ("bitmap: make > bitmap_{get,set}_value8() use bitmap_{read,write}()") switched the > bitmap_get_value8() to an alias of bitmap_read(); the same for 'set'. > > Now; the code that triggers Warray-bounds, calls the function like this: > > #define MAX_BANK 8 > #define BANK_SZ 8 > #define MAX_LINE (MAX_BANK * BANK_SZ) > DECLARE_BITMAP(tval, MAX_LINE); // 64-bit map: unsigned long tval[1] > > read_val |= bitmap_get_value8(tval, i * BANK_SZ) & ~bits; > > bitmap_read() is implemented such that it may conditionally dereference a > pointer beyond the boundary like this: > > unsigned long offset = start % BITS_PER_LONG; > unsigned long space = BITS_PER_LONG - offset; > > if (space >= nbits) > return (map[index] >> offset) & BITMAP_LAST_WORD_MASK(nbits); > > value_low = map[index] & BITMAP_FIRST_WORD_MASK(start); > value_high = map[index + 1] & BITMAP_LAST_WORD_MASK(start + nbits); > return (value_low >> offset) | (value_high << space); > > In case of bitmap_get_value8(), it's impossible to violate the boundary > because 'space >= nbits' is never the true for byte-aligned 8-bit access. > So, this is clearly a false-positive. > > The same type of false-positives break my allmodconfig build in many > places. gcc-8, is clear, however. > > Link: https://lkml.kernel.org/r/20240522225830.1201778-1-yury.norov@xxxxxxxxx > Signed-off-by: Yury Norov <yury.norov@xxxxxxxxx> > Cc: Alexander Lobakin <aleksander.lobakin@xxxxxxxxx> > Cc: David S. Miller <davem@xxxxxxxxxxxxx> > Cc: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx> > Cc: Masahiro Yamada <masahiroy@xxxxxxxxxx> > Cc: Nhat Pham <nphamcs@xxxxxxxxx> > Cc: Petr Mladek <pmladek@xxxxxxxx> > Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxxx> > Cc: Vincent Guittot <vincent.guittot@xxxxxxxxxx> > Cc: Yoann Congal <yoann.congal@xxxxxxxx> > Cc: Arnd Bergmann <arnd@xxxxxxxx> > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > --- > > init/Kconfig | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > --- a/init/Kconfig~gcc-disable-warray-bounds-for-gcc-9 > +++ a/init/Kconfig > @@ -883,7 +883,7 @@ config GCC10_NO_ARRAY_BOUNDS > > config CC_NO_ARRAY_BOUNDS > bool > - default y if CC_IS_GCC && GCC_VERSION >= 100000 && GCC10_NO_ARRAY_BOUNDS > + default y if CC_IS_GCC && GCC_VERSION >= 90000 && GCC10_NO_ARRAY_BOUNDS > > # Currently, disable -Wstringop-overflow for GCC globally. > config GCC_NO_STRINGOP_OVERFLOW > _ > > Patches currently in -mm which might be from yury.norov@xxxxxxxxx are > > gcc-disable-warray-bounds-for-gcc-9.patch
