https://github.com/torvalds/linux
Revision deba0a2af9592b2022a0bce7b085a318b53ce1db authored by cpaul@redhat.com on 04 April 2016, 23:58:47 UTC, committed by Dave Airlie on 21 April 2016, 23:53:17 UTC
With the joys of things running concurrently, there's always a chance that the port we get passed in drm_dp_payload_send_msg() isn't actually valid anymore. Because of this, we need to make sure we validate the reference to the port before we use it otherwise we risk running into various race conditions. For instance, on the Dell MST monitor I have here for testing, hotplugging it enough times causes us to kernel panic: [drm:intel_mst_enable_dp] 1 [drm:drm_dp_update_payload_part2] payload 0 1 [drm:intel_get_hpd_pins] hotplug event received, stat 0x00200000, dig 0x10101011, pins 0x00000020 [drm:intel_hpd_irq_handler] digital hpd port B - short [drm:intel_dp_hpd_pulse] got hpd irq on port B - short [drm:intel_dp_check_mst_status] got esi 00 10 00 [drm:drm_dp_update_payload_part2] payload 1 1 general protection fault: 0000 [#1] SMP … Call Trace: [<ffffffffa012b632>] drm_dp_update_payload_part2+0xc2/0x130 [drm_kms_helper] [<ffffffffa032ef08>] intel_mst_enable_dp+0xf8/0x180 [i915] [<ffffffffa0310dbd>] haswell_crtc_enable+0x3ed/0x8c0 [i915] [<ffffffffa030c84d>] intel_atomic_commit+0x5ad/0x1590 [i915] [<ffffffffa01db877>] ? drm_atomic_set_crtc_for_connector+0x57/0xe0 [drm] [<ffffffffa01dc4e7>] drm_atomic_commit+0x37/0x60 [drm] [<ffffffffa0130a3a>] drm_atomic_helper_set_config+0x7a/0xb0 [drm_kms_helper] [<ffffffffa01cc482>] drm_mode_set_config_internal+0x62/0x100 [drm] [<ffffffffa01d02ad>] drm_mode_setcrtc+0x3cd/0x4e0 [drm] [<ffffffffa01c18e3>] drm_ioctl+0x143/0x510 [drm] [<ffffffffa01cfee0>] ? drm_mode_setplane+0x1b0/0x1b0 [drm] [<ffffffff810f79a7>] ? hrtimer_start_range_ns+0x1b7/0x3a0 [<ffffffff81212962>] do_vfs_ioctl+0x92/0x570 [<ffffffff81590852>] ? __sys_recvmsg+0x42/0x80 [<ffffffff81212eb9>] SyS_ioctl+0x79/0x90 [<ffffffff816b4e32>] entry_SYSCALL_64_fastpath+0x1a/0xa4 RIP [<ffffffffa012b026>] drm_dp_payload_send_msg+0x146/0x1f0 [drm_kms_helper] Which occurs because of the hotplug event shown in the log, which ends up causing DRM's dp helpers to drop the port we're updating the payload on and panic. CC: stable@vger.kernel.org Signed-off-by: Lyude <cpaul@redhat.com> Reviewed-by: David Airlie <airlied@linux.ie> Signed-off-by: Dave Airlie <airlied@redhat.com>
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Tip revision: deba0a2af9592b2022a0bce7b085a318b53ce1db authored by cpaul@redhat.com on 04 April 2016, 23:58:47 UTC
drm/dp/mst: Validate port in drm_dp_payload_send_msg()
drm/dp/mst: Validate port in drm_dp_payload_send_msg()
Tip revision: deba0a2
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