bits_per() rounds up to the next power of two when passed a power of two. This causes crashes on some machines and configurations.

Reported-by: Михаил Новоселов m.novosyolov@rosalinux.ru Tested-by: Ильфат Гаптрахманов i.gaptrakhmanov@rosalinux.ru Link: https://gitlab.freedesktop.org/drm/amd/-/issues/3347 Link: https://lore.kernel.org/all/1c978cf1-2934-4e66-e4b3-e81b04cb3571@rosalinux.r... Fixes: f2d5dcb48f7b (bounds: support non-power-of-two CONFIG_NR_CPUS) Cc: stable@vger.kernel.org Signed-off-by: Matthew Wilcox (Oracle) willy@infradead.org Cc: Rik van Riel riel@surriel.com Cc: Mel Gorman mgorman@techsingularity.net Cc: Peter Zijlstra peterz@infradead.org Cc: Ingo Molnar mingo@kernel.org Cc: Andrew Morton akpm@linux-foundation.org --- kernel/bounds.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bounds.c b/kernel/bounds.c index c5a9fcd2d622..8553368ccf79 100644 --- a/kernel/bounds.c +++ b/kernel/bounds.c @@ -19,7 +19,7 @@ int main(void) DEFINE(NR_PAGEFLAGS, __NR_PAGEFLAGS); DEFINE(MAX_NR_ZONES, __MAX_NR_ZONES); #ifdef CONFIG_SMP - DEFINE(NR_CPUS_BITS, bits_per(CONFIG_NR_CPUS)); + DEFINE(NR_CPUS_BITS, bits_per(CONFIG_NR_CPUS - 1)); #endif DEFINE(SPINLOCK_SIZE, sizeof(spinlock_t)); #ifdef CONFIG_LRU_GEN