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efi: random: fix NULL-deref when refreshing seed

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Do not try to refresh the RNG seed in case the firmware does not support
setting variables.

This is specifically needed to prevent a NULL-pointer dereference on the
Lenovo X13s with some firmware revisions, or more generally, whenever
the runtime services have been disabled (e.g. efi=noruntime or with
PREEMPT_RT).

Fixes: e7b813b32a42 ("efi: random: refresh non-volatile random seed when RNG is initialized")
Reported-by: Steev Klimaszewski <steev@kali.org>
Reported-by: Bjorn Andersson <andersson@kernel.org>
Tested-by: Steev Klimaszewski <steev@kali.org>
Tested-by: Andrew Halaney <ahalaney@redhat.com> # sc8280xp-lenovo-thinkpad-x13s
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
This commit is contained in:
Johan Hovold 2022-12-16 10:15:14 +01:00 committed by Jason A. Donenfeld
parent 6bb20c152b
commit 41a15855c1
1 changed files with 3 additions and 1 deletions
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4
drivers/firmware/efi/efi.c
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@ -429,7 +429,9 @@ static int __init efisubsys_init(void)
platform_device_register_simple("efi_secret", 0, NULL, 0);
#endif
execute_with_initialized_rng(&refresh_nv_rng_seed_nb);
if (efi_rt_services_supported(EFI_RT_SUPPORTED_SET_VARIABLE))
execute_with_initialized_rng(&refresh_nv_rng_seed_nb);
return 0;
err_remove_group: