| Message ID | 20220124202951.28579-5-linux@dominikbrodowski.net |
|---|---|
| State | Accepted |
| Commit | f4f7c153a61782f3fb259d0f39aab91444e555d9 |
| Headers | show |
| Series | [1/6] hw_random: explicit ordering of initcalls | expand |
diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c index 9405fcdace38..bc9f95cbac92 100644 --- a/drivers/char/hw_random/core.c +++ b/drivers/char/hw_random/core.c @@ -429,6 +429,9 @@ static int hwrng_fillfn(void *unused) while (!kthread_should_stop()) { struct hwrng *rng; + if (!current_quality) + break; + rng = get_current_rng(); if (IS_ERR(rng) || !rng) break;
For two reasons, current_quality may become zero within the rngd kernel thread: (1) The user lowers current_quality to 0 by writing to the sysfs module parameter file (note that increasing the quality from zero is without effect at the moment), or (2) there are two or more hwrng devices registered, and those which provide quality>0 are unregistered, but one with quality==0 remains. If current_quality is 0, the randomness is not trusted and cannot help to increase the entropy count. That will lead to continuous calls to the hwrngd thread and continuous stirring of the input pool with untrusted bits. Cc: Matt Mackall <mpm@selenic.com> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: Jason A. Donenfeld <Jason@zx2c4.com> Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net> --- drivers/char/hw_random/core.c | 3 +++ 1 file changed, 3 insertions(+)