On 25/11/2018 02:21, Lyude Paul wrote:

Currently on driver bringup with KASAN enabled, meson triggers an OOB memory access as shown below:

[ 117.904528] ================================================================== [ 117.904560] BUG: KASAN: global-out-of-bounds in meson_viu_set_osd_lut+0x7a0/0x890 [ 117.904588] Read of size 4 at addr ffff20000a63ce24 by task systemd-udevd/498 [ 117.904601] [ 118.083372] CPU: 4 PID: 498 Comm: systemd-udevd Not tainted 4.20.0-rc3Lyude-Test+ #20 [ 118.091143] Hardware name: amlogic khadas-vim2/khadas-vim2, BIOS 2018.07-rc2-armbian 09/11/2018 [ 118.099768] Call trace: [ 118.102181] dump_backtrace+0x0/0x3e8 [ 118.105796] show_stack+0x14/0x20 [ 118.109083] dump_stack+0x130/0x1c4 [ 118.112539] print_address_description+0x60/0x25c [ 118.117214] kasan_report+0x1b4/0x368 [ 118.120851] __asan_report_load4_noabort+0x18/0x20 [ 118.125566] meson_viu_set_osd_lut+0x7a0/0x890 [ 118.129953] meson_viu_init+0x10c/0x290 [ 118.133741] meson_drv_bind_master+0x474/0x748 [ 118.138141] meson_drv_bind+0x10/0x18 [ 118.141760] try_to_bring_up_master+0x3d8/0x768 [ 118.146249] component_add+0x214/0x570 [ 118.149978] meson_dw_hdmi_probe+0x18/0x20 [meson_dw_hdmi] [ 118.155404] platform_drv_probe+0x98/0x138 [ 118.159455] really_probe+0x2a0/0xa70 [ 118.163070] driver_probe_device+0x1b4/0x2d8 [ 118.167299] __driver_attach+0x200/0x280 [ 118.171189] bus_for_each_dev+0x10c/0x1a8 [ 118.175144] driver_attach+0x38/0x50 [ 118.178681] bus_add_driver+0x330/0x608 [ 118.182471] driver_register+0x140/0x388 [ 118.186361] __platform_driver_register+0xc8/0x108 [ 118.191117] meson_dw_hdmi_platform_driver_init+0x1c/0x1000 [meson_dw_hdmi] [ 118.198022] do_one_initcall+0x12c/0x3bc [ 118.201883] do_init_module+0x1fc/0x638 [ 118.205673] load_module+0x4b4c/0x6808 [ 118.209387] __se_sys_init_module+0x2e8/0x3c0 [ 118.213699] __arm64_sys_init_module+0x68/0x98 [ 118.218100] el0_svc_common+0x104/0x210 [ 118.221893] el0_svc_handler+0x48/0xb8 [ 118.225594] el0_svc+0x8/0xc [ 118.228429] [ 118.229887] The buggy address belongs to the variable: [ 118.235007] eotf_33_linear_mapping+0x84/0xc0 [ 118.239301] [ 118.240752] Memory state around the buggy address: [ 118.245522] ffff20000a63cd00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 [ 118.252695] ffff20000a63cd80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 [ 118.259850] >ffff20000a63ce00: 00 00 00 00 04 fa fa fa fa fa fa fa 00 00 00 00 [ 118.267000] ^ [ 118.271222] ffff20000a63ce80: 00 fa fa fa fa fa fa fa 00 00 00 00 00 00 00 00 [ 118.278393] ffff20000a63cf00: 00 00 00 00 00 00 00 00 00 00 00 00 04 fa fa fa [ 118.285542] ================================================================== [ 118.292699] Disabling lock debugging due to kernel taint

It seems that when looping through the OSD EOTF LUT maps, we use the same max iterator for OETF: 20. This is wrong though, since 20*2 is 40, which means that we'll stop out of bounds on the EOTF maps.

But, this whole thing is already confusing enough to read through as-is, so let's just replace all of the hardcoded sizes with OSD_(OETF/EOTF)_LUT_SIZE / 2.

Signed-off-by: Lyude Paul lyude@redhat.com Fixes: bbbe775ec5b5 ("drm: Add support for Amlogic Meson Graphic Controller") Cc: Neil Armstrong narmstrong@baylibre.com Cc: Maxime Ripard maxime.ripard@bootlin.com Cc: Carlo Caione carlo@caione.org Cc: Kevin Hilman khilman@baylibre.com Cc: dri-devel@lists.freedesktop.org Cc: linux-amlogic@lists.infradead.org Cc: linux-arm-kernel@lists.infradead.org Cc: stable@vger.kernel.org # v4.10+

---

drivers/gpu/drm/meson/meson_viu.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/meson/meson_viu.c b/drivers/gpu/drm/meson/meson_viu.c index 6bcfa527c180..26a0857878bf 100644 --- a/drivers/gpu/drm/meson/meson_viu.c +++ b/drivers/gpu/drm/meson/meson_viu.c @@ -184,18 +184,18 @@ void meson_viu_set_osd_lut(struct meson_drm *priv, enum viu_lut_sel_e lut_sel, if (lut_sel == VIU_LUT_OSD_OETF) { writel(0, priv->io_base + _REG(addr_port));

• for (i = 0; i < 20; i++)
  

• for (i = 0; i < (OSD_OETF_LUT_SIZE / 2); i++)
  writel(r_map[i * 2] | (r_map[i * 2 + 1] << 16),
  	priv->io_base + _REG(data_port));
  

writel(r_map[OSD_OETF_LUT_SIZE - 1] | (g_map[0] << 16), priv->io_base + _REG(data_port));

• for (i = 0; i < 20; i++)
  

• for (i = 0; i < (OSD_OETF_LUT_SIZE / 2); i++)
  writel(g_map[i * 2 + 1] | (g_map[i * 2 + 2] << 16),
  	priv->io_base + _REG(data_port));
  

• for (i = 0; i < 20; i++)
  

• for (i = 0; i < (OSD_OETF_LUT_SIZE / 2); i++)
  writel(b_map[i * 2] | (b_map[i * 2 + 1] << 16),
  	priv->io_base + _REG(data_port));
  

@@ -211,18 +211,18 @@ void meson_viu_set_osd_lut(struct meson_drm *priv, enum viu_lut_sel_e lut_sel, } else if (lut_sel == VIU_LUT_OSD_EOTF) { writel(0, priv->io_base + _REG(addr_port));

• for (i = 0; i < 20; i++)
  

• for (i = 0; i < (OSD_EOTF_LUT_SIZE / 2); i++)
  writel(r_map[i * 2] | (r_map[i * 2 + 1] << 16),
  	priv->io_base + _REG(data_port));
  

writel(r_map[OSD_EOTF_LUT_SIZE - 1] | (g_map[0] << 16), priv->io_base + _REG(data_port));

• for (i = 0; i < 20; i++)
  

• for (i = 0; i < (OSD_EOTF_LUT_SIZE / 2); i++)
  writel(g_map[i * 2 + 1] | (g_map[i * 2 + 2] << 16),
  	priv->io_base + _REG(data_port));
  

• for (i = 0; i < 20; i++)
  

• for (i = 0; i < (OSD_EOTF_LUT_SIZE / 2); i++)
  writel(b_map[i * 2] | (b_map[i * 2 + 1] << 16),
  	priv->io_base + _REG(data_port));
  

Good catch ! Acked-by: Neil Armstrong narmstrong@baylibre.com

Applying to drm-misc-fixes

Thanks, Neil