Messages in this thread | | | Date | Mon, 18 Mar 2024 21:00:42 +0100 | From | "Jason A. Donenfeld" <> | Subject | Re: [PATCH] random: Fix the issue of '_might_sleep' function running in an atomic contex |
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Hi Guoyong,
On Mon, Mar 18, 2024 at 03:53:27PM +0800, Guoyong Wang wrote: > 'input_handle_event' runs in an atomic context > (spinlock). In rare instances, it may call > the '_might_sleep' function, which could trigger > a kernel exception. > > Backtrace: > [<ffffffd613025ba0>] die+0xa8/0x2fc > [<ffffffd613027428>] bug_handler+0x44/0xec > [<ffffffd613016964>] brk_handler+0x90/0x144 > [<ffffffd613041e58>] do_debug_exception+0xa0/0x148 > [<ffffffd61400c208>] el1_dbg+0x60/0x7c > [<ffffffd61400c000>] el1h_64_sync_handler+0x38/0x90 > [<ffffffd613011294>] el1h_64_sync+0x64/0x6c > [<ffffffd613102d88>] __might_resched+0x1fc/0x2e8 > [<ffffffd613102b54>] __might_sleep+0x44/0x7c > [<ffffffd6130b6eac>] cpus_read_lock+0x1c/0xec > [<ffffffd6132c2820>] static_key_enable+0x14/0x38 > [<ffffffd61400ac08>] crng_set_ready+0x14/0x28 > [<ffffffd6130df4dc>] execute_in_process_context+0xb8/0xf8 > [<ffffffd61400ab30>] _credit_init_bits+0x118/0x1dc > [<ffffffd6138580c8>] add_timer_randomness+0x264/0x270 > [<ffffffd613857e54>] add_input_randomness+0x38/0x48 > [<ffffffd613a80f94>] input_handle_event+0x2b8/0x490 > [<ffffffd613a81310>] input_event+0x6c/0x98
Thanks for reporting this.
I'm wondering, though, rather than introducing a second function, maybe execute_in_process_context() should just gain a `&& !in_atomic()`. That'd make things a bit simpler.
However, I'm pretty sure in_atomic() isn't actually a reliable way of determining that, depending on config. So maybe this should just call the worker always (if system_wq isn't null).
Alternatively, any chance the call to add_input_randomness() could be moved outside the spinlock, or does this not look possible?
Jason
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