In lock_region, simplify the calculation of the region_width parameter. This field is the size, but encoded as log2(ceil(size)) - 1. log2(ceil(size)) may be computed directly as fls(size - 1). However, we want to use the 64-bit versions as the amount to lock can exceed 32-bits.
This avoids undefined behaviour when locking all memory (size ~0), caught by UBSAN.
Signed-off-by: Alyssa Rosenzweig alyssa.rosenzweig@collabora.com Reported-and-tested-by: Chris Morgan macromorgan@hotmail.com Cc: stable@vger.kernel.org --- drivers/gpu/drm/panfrost/panfrost_mmu.c | 19 +++++-------------- 1 file changed, 5 insertions(+), 14 deletions(-)
diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c b/drivers/gpu/drm/panfrost/panfrost_mmu.c index 0da5b3100ab1..f6e02d0392f4 100644 --- a/drivers/gpu/drm/panfrost/panfrost_mmu.c +++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c @@ -62,21 +62,12 @@ static void lock_region(struct panfrost_device *pfdev, u32 as_nr, { u8 region_width; u64 region = iova & PAGE_MASK; - /* - * fls returns: - * 1 .. 32 - * - * 10 + fls(num_pages) - * results in the range (11 .. 42) - */ - - size = round_up(size, PAGE_SIZE);
- region_width = 10 + fls(size >> PAGE_SHIFT); - if ((size >> PAGE_SHIFT) != (1ul << (region_width - 11))) { - /* not pow2, so must go up to the next pow2 */ - region_width += 1; - } + /* The size is encoded as ceil(log2) minus(1), which may be calculated + * with fls. The size must be clamped to hardware bounds. + */ + size = max_t(u64, size, PAGE_SIZE); + region_width = fls64(size - 1) - 1; region |= region_width;
/* Lock the region that needs to be updated */