Messages in this thread | | | Subject | Re: [PATCH v2] x86, random: Fix get_random_bytes() warning in x86 start_kernel | From | Prarit Bhargava <> | Date | Sun, 3 Feb 2019 08:09:37 -0500 |
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On 2/1/19 10:02 PM, Theodore Y. Ts'o wrote: > On Fri, Feb 01, 2019 at 01:08:31PM -0500, Prarit Bhargava wrote: >> After 43838a23a05f ("random: fix crng_ready() test") early boot calls to >> get_random_bytes() will warn on x86 because the crng is not initialized. >> For example, >> >> random: get_random_bytes called from start_kernel+0x8e/0x587 with crng_init=0 >> >> x86 only uses get_random_bytes() for better randomization of the stack >> canary value so the warning is of no consequence. >> >> Test if the crng is initialized before calling get_random_bytes(). If it >> is not available then attempt to read from the hardware random generator, >> before finally using the TSC. > > If you want to trust the CPU's hardware number generator, there is a > way to do this already. Simply enable CONFIG_RANDOM_TRUST_CPU, or set > the boot command line option "random.trust_cpu=on". > Ted, the bug I'm trying to fix is the warning:
random: get_random_bytes called from start_kernel+0x8e/0x587 with crng_init=0
during early boot. Even with the kernel parameter the warning appears.
> Also, relying on the TSC for entropy is not something we should be > recommending.
The current code uses the TSC. It is not something new I'm introducing.
P.
> > So, NAK. > > - Ted >
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