On Tue, Nov 29, 2016 at 7:02 AM, Chris Wilson <chris at chris-wilson.co.uk>
wrote:
> The fb_helper->connector_count is modified when a new connector is
> constructed following a hotplug event (e.g. DP-MST). This causes trouble
> for drm_setup_crtcs() and friends that assume that fb_helper is
> constant:
>
> [ 1250.872997] BUG: KASAN: slab-out-of-bounds in drm_setup_crtcs+0x320/0xf80
> at addr ffff88074cdd2608
> [ 1250.873020] Write of size 40 by task kworker/u8:3/480
> [ 1250.873039] CPU: 2 PID: 480 Comm: kworker/u8:3 Tainted: G U
> 4.9.0-rc6+ #285
> [ 1250.873043] Hardware name: /NUC6i3SYB, BIOS
> SYSKLi35.86A.0024.2015.1027.2142 10/27/2015
> [ 1250.873050] Workqueue: events_unbound async_run_entry_fn
> [ 1250.873056] ffff88070f9d78f0 ffffffff814b72aa ffff88074e40c5c0
> ffff88074cdd2608
> [ 1250.873067] ffff88070f9d7918 ffffffff8124ff3c ffff88070f9d79b0
> ffff88074cdd2600
> [ 1250.873079] ffff88074e40c5c0 ffff88070f9d79a0 ffffffff812501e4
> 0000000000000005
> [ 1250.873090] Call Trace:
> [ 1250.873099] [<ffffffff814b72aa>] dump_stack+0x67/0x9d
> [ 1250.873106] [<ffffffff8124ff3c>] kasan_object_err+0x1c/0x70
> [ 1250.873113] [<ffffffff812501e4>] kasan_report_error+0x204/0x4f0
> [ 1250.873120] [<ffffffff81698df0>] ? drm_dev_printk+0x140/0x140
> [ 1250.873127] [<ffffffff81250ac3>] kasan_report+0x53/0x60
> [ 1250.873134] [<ffffffff81688b40>] ? drm_setup_crtcs+0x320/0xf80
> [ 1250.873142] [<ffffffff8124f18e>] check_memory_region+0x13e/0x1a0
> [ 1250.873147] [<ffffffff8124f5f3>] memset+0x23/0x40
> [ 1250.873154] [<ffffffff81688b40>] drm_setup_crtcs+0x320/0xf80
> [ 1250.873161] [<ffffffff810be7c5>] ? wake_up_q+0x45/0x80
> [ 1250.873169] [<ffffffff81b0c180>] ? mutex_lock_nested+0x5a0/0x5a0
> [ 1250.873176] [<ffffffff8168a0e6>] drm_fb_helper_initial_config+0x206/0x7a0
> [ 1250.873183] [<ffffffff81689ee0>] ? drm_fb_helper_set_par+0x90/0x90
> [ 1250.873303] [<ffffffffa0b68690>] ? intel_fbdev_fini+0x140/0x140 [i915]
> [ 1250.873387] [<ffffffffa0b686b2>] intel_fbdev_initial_config+0x22/0x40
> [i915]
> [ 1250.873391] [<ffffffff810b50ff>] async_run_entry_fn+0x7f/0x270
> [ 1250.873394] [<ffffffff810a64b0>] process_one_work+0x3d0/0x960
> [ 1250.873398] [<ffffffff810a641d>] ? process_one_work+0x33d/0x960
> [ 1250.873401] [<ffffffff810a60e0>] ? max_active_store+0xf0/0xf0
> [ 1250.873406] [<ffffffff810f6f9d>] ? do_raw_spin_lock+0x10d/0x1a0
> [ 1250.873413] [<ffffffff810a767d>] worker_thread+0x8d/0x840
> [ 1250.873419] [<ffffffff810a75f0>] ? create_worker+0x2e0/0x2e0
> [ 1250.873426] [<ffffffff810b0454>] kthread+0x194/0x1c0
> [ 1250.873432] [<ffffffff810b02c0>] ? kthread_park+0x60/0x60
> [ 1250.873438] [<ffffffff810f095d>] ? trace_hardirqs_on+0xd/0x10
> [ 1250.873446] [<ffffffff810b02c0>] ? kthread_park+0x60/0x60
> [ 1250.873453] [<ffffffff810b02c0>] ? kthread_park+0x60/0x60
> [ 1250.873457] [<ffffffff81b12277>] ret_from_fork+0x27/0x40
> [ 1250.873460] Object at ffff88074cdd2608, in cache kmalloc-32 size: 32
>
> However, when holding the mode_config.lock around the fb_helper, we have
> to be careful of any callbacks that may reenter the fb_helper and so try
> to reacquire the mode_config.lock (e.g. register_framebuffer). To avoid
> the mutex recursion, we have to rearrange the sequence to move the
> registration into the caller outside of the mode_config.lock.
>
> v2: drop the 1; following the lockdep assertion inside the for(;;), I
> anticipated an error that doesn't happen!
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=98826
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Daniel Vetter <daniel at ffwll.ch>
Applied to drm-misc
Sean
> ---
> drivers/gpu/drm/drm_fb_helper.c | 73
> ++++++++++++++++++++++-------------------
> 1 file changed, 40 insertions(+), 33 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index 1f26634f53d8..380a0ec01033 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -97,6 +97,10 @@ static LIST_HEAD(kernel_fb_helper_list);
> * mmap page writes.
> */
>
> +#define drm_fb_helper_for_each_connector(fbh, i__) \
> + for (({ lockdep_assert_held(&(fbh)->dev->mode_config.mutex); }), \
> + i__ = 0; i__ < (fbh)->connector_count; i__++)
> +
> /**
> * drm_fb_helper_single_add_all_connectors() - add all connectors to fbdev
> * emulation helper
> @@ -130,7 +134,7 @@ int drm_fb_helper_single_add_all_connectors(struct
> drm_fb_helper *fb_helper)
> mutex_unlock(&dev->mode_config.mutex);
> return 0;
> fail:
> - for (i = 0; i < fb_helper->connector_count; i++) {
> + drm_fb_helper_for_each_connector(fb_helper, i) {
> struct drm_fb_helper_connector *fb_helper_connector =
> fb_helper->connector_info[i];
>
> @@ -565,7 +569,7 @@ static void drm_fb_helper_dpms(struct fb_info *info, int
> dpms_mode)
> continue;
>
> /* Walk the connectors & encoders on this fb turning them
> on/off */
> - for (j = 0; j < fb_helper->connector_count; j++) {
> + drm_fb_helper_for_each_connector(fb_helper, j) {
> connector = fb_helper->connector_info[j]->connector;
> connector->funcs->dpms(connector, dpms_mode);
> drm_object_property_set_value(&connector->base,
> @@ -1469,7 +1473,6 @@ static int drm_fb_helper_single_fb_probe(struct
> drm_fb_helper *fb_helper,
> int ret = 0;
> int crtc_count = 0;
> int i;
> - struct fb_info *info;
> struct drm_fb_helper_surface_size sizes;
> int gamma_size = 0;
>
> @@ -1485,7 +1488,7 @@ static int drm_fb_helper_single_fb_probe(struct
> drm_fb_helper *fb_helper,
> sizes.surface_depth = sizes.surface_bpp = preferred_bpp;
>
> /* first up get a count of crtcs now in use and new min/maxes
> width/heights */
> - for (i = 0; i < fb_helper->connector_count; i++) {
> + drm_fb_helper_for_each_connector(fb_helper, i) {
> struct drm_fb_helper_connector *fb_helper_conn =
> fb_helper->connector_info[i];
> struct drm_cmdline_mode *cmdline_mode;
>
> @@ -1572,8 +1575,6 @@ static int drm_fb_helper_single_fb_probe(struct
> drm_fb_helper *fb_helper,
> if (ret < 0)
> return ret;
>
> - info = fb_helper->fbdev;
> -
> /*
> * Set the fb pointer - usually drm_setup_crtcs does this for hotplug
> * events, but at init time drm_setup_crtcs needs to be called before
> @@ -1585,20 +1586,6 @@ static int drm_fb_helper_single_fb_probe(struct
> drm_fb_helper *fb_helper,
> if (fb_helper->crtc_info[i].mode_set.num_connectors)
> fb_helper->crtc_info[i].mode_set.fb = fb_helper->fb;
>
> -
> - info->var.pixclock = 0;
> - if (register_framebuffer(info) < 0)
> - return -EINVAL;
> -
> - dev_info(fb_helper->dev->dev, "fb%d: %s frame buffer device\n",
> - info->node, info->fix.id);
> -
> - if (list_empty(&kernel_fb_helper_list)) {
> - register_sysrq_key('v', &sysrq_drm_fb_helper_restore_op);
> - }
> -
> - list_add(&fb_helper->kernel_fb_list, &kernel_fb_helper_list);
> -
> return 0;
> }
>
> @@ -1730,7 +1717,7 @@ static int drm_fb_helper_probe_connector_modes(struct
> drm_fb_helper *fb_helper,
> int count = 0;
> int i;
>
> - for (i = 0; i < fb_helper->connector_count; i++) {
> + drm_fb_helper_for_each_connector(fb_helper, i) {
> connector = fb_helper->connector_info[i]->connector;
> count += connector->funcs->fill_modes(connector, maxX, maxY);
> }
> @@ -1830,7 +1817,7 @@ static void drm_enable_connectors(struct drm_fb_helper
> *fb_helper,
> struct drm_connector *connector;
> int i = 0;
>
> - for (i = 0; i < fb_helper->connector_count; i++) {
> + drm_fb_helper_for_each_connector(fb_helper, i) {
> connector = fb_helper->connector_info[i]->connector;
> enabled[i] = drm_connector_enabled(connector, true);
> DRM_DEBUG_KMS("connector %d enabled? %s\n",
> connector->base.id,
> @@ -1841,7 +1828,7 @@ static void drm_enable_connectors(struct drm_fb_helper
> *fb_helper,
> if (any_enabled)
> return;
>
> - for (i = 0; i < fb_helper->connector_count; i++) {
> + drm_fb_helper_for_each_connector(fb_helper, i) {
> connector = fb_helper->connector_info[i]->connector;
> enabled[i] = drm_connector_enabled(connector, false);
> }
> @@ -1862,7 +1849,7 @@ static bool drm_target_cloned(struct drm_fb_helper
> *fb_helper,
> return false;
>
> count = 0;
> - for (i = 0; i < fb_helper->connector_count; i++) {
> + drm_fb_helper_for_each_connector(fb_helper, i) {
> if (enabled[i])
> count++;
> }
> @@ -1873,7 +1860,7 @@ static bool drm_target_cloned(struct drm_fb_helper
> *fb_helper,
>
> /* check the command line or if nothing common pick 1024x768 */
> can_clone = true;
> - for (i = 0; i < fb_helper->connector_count; i++) {
> + drm_fb_helper_for_each_connector(fb_helper, i) {
> if (!enabled[i])
> continue;
> fb_helper_conn = fb_helper->connector_info[i];
> @@ -1899,8 +1886,7 @@ static bool drm_target_cloned(struct drm_fb_helper
> *fb_helper,
> can_clone = true;
> dmt_mode = drm_mode_find_dmt(fb_helper->dev, 1024, 768, 60, false);
>
> - for (i = 0; i < fb_helper->connector_count; i++) {
> -
> + drm_fb_helper_for_each_connector(fb_helper, i) {
> if (!enabled[i])
> continue;
>
> @@ -1931,7 +1917,7 @@ static int drm_get_tile_offsets(struct drm_fb_helper
> *fb_helper,
> int i;
> int hoffset = 0, voffset = 0;
>
> - for (i = 0; i < fb_helper->connector_count; i++) {
> + drm_fb_helper_for_each_connector(fb_helper, i) {
> fb_helper_conn = fb_helper->connector_info[i];
> if (!fb_helper_conn->connector->has_tile)
> continue;
> @@ -1965,7 +1951,7 @@ static bool drm_target_preferred(struct drm_fb_helper
> *fb_helper,
> int i;
>
> retry:
> - for (i = 0; i < fb_helper->connector_count; i++) {
> + drm_fb_helper_for_each_connector(fb_helper, i) {
> fb_helper_conn = fb_helper->connector_info[i];
>
> if (conn_configured & BIT_ULL(i))
> @@ -2128,6 +2114,9 @@ static void drm_setup_crtcs(struct drm_fb_helper
> *fb_helper)
> width = dev->mode_config.max_width;
> height = dev->mode_config.max_height;
>
> + /* prevent concurrent modification of connector_count by hotplug */
> + lockdep_assert_held(&fb_helper->dev->mode_config.mutex);
> +
> crtcs = kcalloc(fb_helper->connector_count,
> sizeof(struct drm_fb_helper_crtc *), GFP_KERNEL);
> modes = kcalloc(fb_helper->connector_count,
> @@ -2141,7 +2130,6 @@ static void drm_setup_crtcs(struct drm_fb_helper
> *fb_helper)
> goto out;
> }
>
> -
> drm_enable_connectors(fb_helper, enabled);
>
> if (!(fb_helper->funcs->initial_config &&
> @@ -2170,7 +2158,7 @@ static void drm_setup_crtcs(struct drm_fb_helper
> *fb_helper)
> drm_fb_helper_modeset_release(fb_helper,
>
> &fb_helper->crtc_info[i].mode_set);
>
> - for (i = 0; i < fb_helper->connector_count; i++) {
> + drm_fb_helper_for_each_connector(fb_helper, i) {
> struct drm_display_mode *mode = modes[i];
> struct drm_fb_helper_crtc *fb_crtc = crtcs[i];
> struct drm_fb_offset *offset = &offsets[i];
> @@ -2247,7 +2235,9 @@ static void drm_setup_crtcs(struct drm_fb_helper
> *fb_helper)
> int drm_fb_helper_initial_config(struct drm_fb_helper *fb_helper, int
> bpp_sel)
> {
> struct drm_device *dev = fb_helper->dev;
> + struct fb_info *info;
> int count = 0;
> + int ret;
>
> if (!drm_fbdev_emulation)
> return 0;
> @@ -2256,7 +2246,6 @@ int drm_fb_helper_initial_config(struct drm_fb_helper
> *fb_helper, int bpp_sel)
> count = drm_fb_helper_probe_connector_modes(fb_helper,
>
> dev->mode_config.max_width,
>
> dev->mode_config.max_height);
> - mutex_unlock(&dev->mode_config.mutex);
> /*
> * we shouldn't end up with no modes here.
> */
> @@ -2264,8 +2253,26 @@ int drm_fb_helper_initial_config(struct drm_fb_helper
> *fb_helper, int bpp_sel)
> dev_info(fb_helper->dev->dev, "No connectors reported
> connected with modes\n");
>
> drm_setup_crtcs(fb_helper);
> + ret = drm_fb_helper_single_fb_probe(fb_helper, bpp_sel);
> + mutex_unlock(&dev->mode_config.mutex);
> + if (ret)
> + return ret;
>
> - return drm_fb_helper_single_fb_probe(fb_helper, bpp_sel);
> + info = fb_helper->fbdev;
> + info->var.pixclock = 0;
> + ret = register_framebuffer(info);
> + if (ret < 0)
> + return ret;
> +
> + dev_info(dev->dev, "fb%d: %s frame buffer device\n",
> + info->node, info->fix.id);
> +
> + if (list_empty(&kernel_fb_helper_list))
> + register_sysrq_key('v', &sysrq_drm_fb_helper_restore_op);
> +
> + list_add(&fb_helper->kernel_fb_list, &kernel_fb_helper_list);
> +
> + return 0;
> }
> EXPORT_SYMBOL(drm_fb_helper_initial_config);
>
> --
> 2.10.2
>
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> Intel-gfx at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
