Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

drm/vc4: drop all currently held locks if deadlock happens

If vc4_hdmi_reset_link() returns -EDEADLK, it means that a deadlock happened in the locking context. This situation should be addressed by dropping all currently held locks and block until the contended lock becomes available. Currently, vc4 is not dealing with the deadlock properly, producing the following output when PROVE_LOCKING is enabled:

[ 825.612809] ------------[ cut here ]------------ [ 825.612852] WARNING: CPU: 1 PID: 116 at drivers/gpu/drm/drm_modeset_lock.c:276 drm_modeset_drop_locks+0x60/0x68 [drm] [ 825.613458] Modules linked in: 8021q mrp garp stp llc raspberrypi_cpufreq brcmfmac brcmutil crct10dif_ce hci_uart cfg80211 btqca btbcm bluetooth vc4 raspberrypi_hwmon snd_soc_hdmi_codec cec clk_raspberrypi ecdh_generic drm_display_helper ecc rfkill drm_dma_helper drm_kms_helper pwm_bcm2835 bcm2835_thermal bcm2835_rng rng_core i2c_bcm2835 drm fuse ip_tables x_tables ipv6 [ 825.613735] CPU: 1 PID: 116 Comm: kworker/1:2 Tainted: G W 6.1.0-rc6-01399-g941aae326315 #3 [ 825.613759] Hardware name: Raspberry Pi 3 Model B Rev 1.2 (DT) [ 825.613777] Workqueue: events output_poll_execute [drm_kms_helper] [ 825.614038] pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) [ 825.614063] pc : drm_modeset_drop_locks+0x60/0x68 [drm] [ 825.614603] lr : drm_helper_probe_detect+0x120/0x1b4 [drm_kms_helper] [ 825.614829] sp : ffff…