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livepatch: add locking to force and signal functions
klp_send_signals() and klp_force_transition() do not acquire klp_mutex, because it seemed to be superfluous. A potential race in klp_send_signals() was harmless and there was nothing in klp_force_transition() which needed to be synchronized. That changed with the addition of klp_forced variable during the review process. There is a small window now, when klp_complete_transition() does not see klp_forced set to true while all tasks have been already transitioned to the target state. module_put() is called and the module can be removed. Acquire klp_mutex in sysfs callback to prevent it. Do the same for the signal sending just to be sure. There is no real downside to that. Fixes: c99a2be ("livepatch: force transition to finish") Fixes: 43347d5 ("livepatch: send a fake signal to all blocking tasks") Reported-by: Jason Baron <[email protected]> Signed-off-by: Miroslav Benes <[email protected]> Reviewed-by: Petr Mladek <[email protected]> Acked-by: Josh Poimboeuf <[email protected]> Signed-off-by: Jiri Kosina <[email protected]>
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