random: fix data race on crng init time

stable inclusion
from stable-v5.10.92
commit 61cca7d191c7c143bc8f3e779859f8b3d5100c89
bugzilla: 186193 https://gitee.com/openeuler/kernel/issues/I53108

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=61cca7d191c7c143bc8f3e779859f8b3d5100c89



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commit 009ba856 upstream.

_extract_crng() does plain loads of crng->init_time and
crng_global_init_time, which causes undefined behavior if
crng_reseed() and RNDRESEEDCRNG modify these corrently.

Use READ_ONCE() and WRITE_ONCE() to make the behavior defined.

Don't fix the race on crng->init_time by protecting it with crng->lock,
since it's not a problem for duplicate reseedings to occur.  I.e., the
lockless access with READ_ONCE() is fine.

Fixes: d848e5f8 ("random: add new ioctl RNDRESEEDCRNG")
Fixes: e192be9d ("random: replace non-blocking pool with a Chacha20-based CRNG")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>
Acked-by: Xie XiuQi <xiexiuqi@huawei.com>