CVE-2022-50491 — coresight: cti: Fix hang in cti_disable_hw()

Affected: Linux

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

coresight: cti: Fix hang in cti_disable_hw()

cti_enable_hw() and cti_disable_hw() are called from an atomic context so shouldn't use runtime PM because it can result in a sleep when communicating with firmware.

Since commit 3c6656337852 ("Revert "firmware: arm_scmi: Add clock management to the SCMI power domain""), this causes a hang on Juno when running the Perf Coresight tests or running this command:

perf record -e cs_etm//u -- ls

This was also missed until the revert commit because pm_runtime_put() was called with the wrong device until commit 692c9a499b28 ("coresight: cti: Correct the parameter for pm_runtime_put")

With lock and scheduler debugging enabled the following is output:

coresight cti_sys0: cti_enable_hw -- dev:cti_sys0 parent: 20020000.cti BUG: sleeping function called from invalid context at drivers/base/power/runtime.c:1151 in_atomic(): 1, irqs_disabled(): 128, non_block: 0, pid: 330, name: perf-exec preempt_count: 2, expected: 0 RCU nest depth: 0, expected: 0 INFO: lockdep is turned off. irq event stamp: 0 hardirqs last enabled at (0): [<0000000000000000>] 0x0 hardirqs last disabled at (0): [<ffff80000822b394>] copy_process+0xa0c/0x1948 softirqs last enabled at (0): [<ffff80000822b394>] copy_process+0xa0c/0x1948 softirqs last disabled at (0): [<0000000000000000>] 0x0 CPU: 3 PID: 330 Comm: perf-exec Not tainted 6.0.0-00053-g042116d99298 #7…

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CVE-2022-50491 — coresight: cti: Fix hang in cti_disable_hw()