Ubuntu: (CVE-2021-47202): linux vulnerability

Description

In the Linux kernel, the following vulnerability has been resolved: thermal: Fix NULL pointer dereferences in of_thermal_ functions of_parse_thermal_zones() parses the thermal-zones node and registers a thermal_zone device for each subnode. However, if a thermal zone is consuming a thermal sensor and that thermal sensor device hasn't probed yet, an attempt to set trip_point_*_temp for that thermal zone device can cause a NULL pointer dereference. Fix it. console:/sys/class/thermal/thermal_zone87 # echo 120000 > trip_point_0_temp ... Unable to handle kernel NULL pointer dereference at virtual address 0000000000000020 ... Call trace: of_thermal_set_trip_temp+0x40/0xc4 trip_point_temp_store+0xc0/0x1dc dev_attr_store+0x38/0x88 sysfs_kf_write+0x64/0xc0 kernfs_fop_write_iter+0x108/0x1d0 vfs_write+0x2f4/0x368 ksys_write+0x7c/0xec __arm64_sys_write+0x20/0x30 el0_svc_common.llvm.7279915941325364641+0xbc/0x1bc do_el0_svc+0x28/0xa0 el0_svc+0x14/0x24 el0_sync_handler+0x88/0xec el0_sync+0x1c0/0x200 While at it, fix the possible NULL pointer dereference in other functions as well: of_thermal_get_temp(), of_thermal_set_emul_temp(), of_thermal_get_trend().