From: Shixiong Ou <[email protected]> The scale module parameter can be set to 0 via kernel command line or sysfs. When scale is 0, scaled_font_h and scaled_font_w become 0, causing a division by zero in the rows/columns calculation.
Introduce a drm_log_scale() helper that returns scale ?: 1, and use it at all read sites. This avoids a race that a setter-based clamp would have between param_set_uint() and the subsequent check, where another CPU could observe scale == 0. Signed-off-by: Shixiong Ou <[email protected]> --- v1->v2: Introduce a drm_log_scale() helper. drivers/gpu/drm/clients/drm_log.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/drivers/gpu/drm/clients/drm_log.c b/drivers/gpu/drm/clients/drm_log.c index 294b3be1a6b3..9522c1344123 100644 --- a/drivers/gpu/drm/clients/drm_log.c +++ b/drivers/gpu/drm/clients/drm_log.c @@ -29,6 +29,11 @@ static unsigned int scale = 1; module_param(scale, uint, 0444); MODULE_PARM_DESC(scale, "Integer scaling factor for drm_log, default is 1"); +static inline unsigned int drm_log_scale(void) +{ + return scale ?: 1; +} + /** * DOC: overview * @@ -76,13 +81,13 @@ static void drm_log_blit(struct iosys_map *dst, unsigned int dst_pitch, { switch (px_width) { case 2: - drm_draw_blit16(dst, dst_pitch, src, src_pitch, height, width, scale, color); + drm_draw_blit16(dst, dst_pitch, src, src_pitch, height, width, drm_log_scale(), color); break; case 3: - drm_draw_blit24(dst, dst_pitch, src, src_pitch, height, width, scale, color); + drm_draw_blit24(dst, dst_pitch, src, src_pitch, height, width, drm_log_scale(), color); break; case 4: - drm_draw_blit32(dst, dst_pitch, src, src_pitch, height, width, scale, color); + drm_draw_blit32(dst, dst_pitch, src, src_pitch, height, width, drm_log_scale(), color); break; default: WARN_ONCE(1, "Can't blit with pixel width %d\n", px_width); @@ -216,8 +221,8 @@ static int drm_log_setup_modeset(struct drm_client_dev *client, return -ENOMEM; } mode_set->fb = scanout->buffer->fb; - scanout->scaled_font_h = scanout->font->height * scale; - scanout->scaled_font_w = scanout->font->width * scale; + scanout->scaled_font_h = scanout->font->height * drm_log_scale(); + scanout->scaled_font_w = scanout->font->width * drm_log_scale(); scanout->rows = height / scanout->scaled_font_h; scanout->columns = width / scanout->scaled_font_w; scanout->front_color = drm_draw_color_from_xrgb8888(0xffffff, format); -- 2.25.1 No virus found Checked by Hillstone Network AntiVirus
