Chris Wilson 966a6a13c6 drm: Hold mode_config.lock to prevent hotplug whilst setting up crtcs ... 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@chris-wilson.co.uk> Cc: Daniel Vetter <daniel@ffwll.ch> Signed-off-by: Sean Paul <seanpaul@chromium.org> Link: http://patchwork.freedesktop.org/patch/msgid/20161129120217.7344-1-chris@chris-wilson.co.uk		2016-11-29 15:52:32 -05:00
..
drm	drm: Hold mode_config.lock to prevent hotplug whilst setting up crtcs	2016-11-29 15:52:32 -05:00
host1x	drm/tegra: dsi: Enhance runtime power management	2016-08-24 15:58:57 +02:00
ipu-v3	imx-drm plane update cleanup, YUV formats	2016-11-11 09:31:27 +10:00
vga	vgaarb: use valid dev pointer in vgaarb_info()	2016-11-22 16:40:35 +01:00
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