seedrng: reduce MAX_SEED_LEN from 512 to 256

As proposed by Jason.
getrandom() is more likely to block on reads larger than this.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/util-linux/seedrng.c b/util-linux/seedrng.c
index 2965f3d47..04e52a996 100644
--- a/util-linux/seedrng.c
+++ b/util-linux/seedrng.c
@@ -56,7 +56,11 @@
 
 enum {
         MIN_SEED_LEN = SHA256_OUTSIZE,
-        MAX_SEED_LEN = 512
+        /* kernels < 5.18 could return short reads from getrandom()
+         * if signal is pending and length is > 256.
+         * Let's limit our reads to 256 bytes.
+         */
+        MAX_SEED_LEN = 256,
 };
 
 static size_t determine_optimal_seed_len(void)