On 6/16/22 6:20 AM, Jason A. Donenfeld wrote:
random.c ratelimits how much it warns about uninitialized urandom reads using __ratelimit. When the RNG is finally initialized, it prints the number of missed messages due to ratelimiting.
It has been this way since that functionality was introduced back in 2018. Recently, cc1e127bfa95 ("random: remove ratelimiting for in-kernel unseeded randomness") put a bit more stress on the urandom ratelimiting, which teased out a bug in the implementation.
Specifically, when under pressure, __ratelimit() will print its own message and reset the count back to 0, making the final message at the end less useful. Secondly, it does so as a pr_warn(), which apparently is undesirable for people's CI.
Fortunately, __ratelimit() has the RATELIMIT_MSG_ON_RELEASE flag exactly for this purpose, so we set the flag.
Fixes: 4e00b339e264 ("random: rate limit unseeded randomness warnings") Cc: stable@vger.kernel.org Reported-by: Jon Hunter jonathanh@nvidia.com Reported-by: Ron Economos re@w6rz.net Signed-off-by: Jason A. Donenfeld Jason@zx2c4.com
drivers/char/random.c | 2 +- include/linux/ratelimit_types.h | 12 ++++++++---- 2 files changed, 9 insertions(+), 5 deletions(-)
diff --git a/drivers/char/random.c b/drivers/char/random.c index d0e4c89c4fcb..07a022e24057 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -87,7 +87,7 @@ static struct fasync_struct *fasync; /* Control how we warn userspace. */ static struct ratelimit_state urandom_warning =
- RATELIMIT_STATE_INIT("warn_urandom_randomness", HZ, 3);
- RATELIMIT_STATE_INIT_FLAGS("urandom_warning", HZ, 3, RATELIMIT_MSG_ON_RELEASE); static int ratelimit_disable __read_mostly = IS_ENABLED(CONFIG_WARN_ALL_UNSEEDED_RANDOM); module_param_named(ratelimit_disable, ratelimit_disable, int, 0644);
diff --git a/include/linux/ratelimit_types.h b/include/linux/ratelimit_types.h index c21c7f8103e2..002266693e50 100644 --- a/include/linux/ratelimit_types.h +++ b/include/linux/ratelimit_types.h @@ -23,12 +23,16 @@ struct ratelimit_state { unsigned long flags; }; -#define RATELIMIT_STATE_INIT(name, interval_init, burst_init) { \
.lock = __RAW_SPIN_LOCK_UNLOCKED(name.lock), \.interval = interval_init, \.burst = burst_init, \+#define RATELIMIT_STATE_INIT_FLAGS(name, interval_init, burst_init, flags_init) { \
.lock = __RAW_SPIN_LOCK_UNLOCKED(name.lock), \.interval = interval_init, \.burst = burst_init, \.flags = flags_init, \+#define RATELIMIT_STATE_INIT(name, interval_init, burst_init) \
- RATELIMIT_STATE_INIT_FLAGS(name, interval_init, burst_init, 0)
- #define RATELIMIT_STATE_INIT_DISABLED \ RATELIMIT_STATE_INIT(ratelimit_state, 0, DEFAULT_RATELIMIT_BURST)
Tested on 5.15.48 kernel for RISC-V RV64. Works good, urandom_read_iter warnings are suppressed.
Tested-by: Ron Economos re@w6rz.net