]> git.baikalelectronics.ru Git - kernel.git/commit
drm/dp/mst: Validate port in drm_dp_payload_send_msg()
authorcpaul@redhat.com <cpaul@redhat.com>
Mon, 4 Apr 2016 23:58:47 +0000 (19:58 -0400)
committerDave Airlie <airlied@redhat.com>
Thu, 21 Apr 2016 23:53:17 +0000 (09:53 +1000)
commit812a857974702d6d966dd96882a06f0695e0d741
tree03af9a5bf6f40966c75e47d19a1decc3235eae67
parente80f18051f3ffcd7f5b96a4bd07be4cdc5ae91f7
drm/dp/mst: Validate port in drm_dp_payload_send_msg()

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>
drivers/gpu/drm/drm_dp_mst_topology.c