sanitizes bloom filters to avoid division by zero (#13714)

Pull requests received over the wire can cause a validator to panic
because of division by zero in bloom filters:
https://github.com/solana-labs/solana/blob/af08ba93e/runtime/src/bloom.rs#L86-L88

core/src/crds_gossip_pull.rs

@@ -79,7 +79,7 @@ impl CrdsFilter {
         let seed: u64 = seed.checked_shl(64 - mask_bits).unwrap_or(0x0);
         seed | (!0u64).checked_shr(mask_bits).unwrap_or(!0x0) as u64
     }
-    pub fn max_items(max_bits: f64, false_rate: f64, num_keys: f64) -> f64 {
+    fn max_items(max_bits: f64, false_rate: f64, num_keys: f64) -> f64 {
         let m = max_bits;
         let p = false_rate;
         let k = num_keys;
@@ -93,28 +93,26 @@ impl CrdsFilter {
         let buf = item.as_ref()[..8].try_into().unwrap();
         u64::from_le_bytes(buf)
     }
-    pub fn test_mask_u64(&self, item: u64, ones: u64) -> bool {
-        let bits = item | ones;
-        bits == self.mask
-    }
-    pub fn test_mask(&self, item: &Hash) -> bool {
+    fn test_mask(&self, item: &Hash) -> bool {
         // only consider the highest mask_bits bits from the hash and set the rest to 1.
         let ones = (!0u64).checked_shr(self.mask_bits).unwrap_or(!0u64);
         let bits = Self::hash_as_u64(item) | ones;
         bits == self.mask
     }
-    pub fn add(&mut self, item: &Hash) {
+    #[cfg(test)]
+    fn add(&mut self, item: &Hash) {
         if self.test_mask(item) {
             self.filter.add(item);
         }
     }
-    pub fn contains(&self, item: &Hash) -> bool {
+    #[cfg(test)]
+    fn contains(&self, item: &Hash) -> bool {
         if !self.test_mask(item) {
             return true;
         }
         self.filter.contains(item)
     }
-    pub fn filter_contains(&self, item: &Hash) -> bool {
+    fn filter_contains(&self, item: &Hash) -> bool {
         self.filter.contains(item)
     }
 }

runtime/src/bloom.rs

@@ -3,6 +3,7 @@ use bv::BitVec;
 use fnv::FnvHasher;
 use rand::{self, Rng};
 use serde::{Deserialize, Serialize};
+use solana_sdk::sanitize::{Sanitize, SanitizeError};
 use std::fmt;
 use std::sync::atomic::{AtomicU64, Ordering};
 use std::{cmp, hash::Hasher, marker::PhantomData};
@@ -45,7 +46,16 @@ impl<T: BloomHashIndex> fmt::Debug for Bloom<T> {
     }
 }
 
-impl<T: BloomHashIndex> solana_sdk::sanitize::Sanitize for Bloom<T> {}
+impl<T: BloomHashIndex> Sanitize for Bloom<T> {
+    fn sanitize(&self) -> Result<(), SanitizeError> {
+        // Avoid division by zero in self.pos(...).
+        if self.bits.is_empty() {
+            Err(SanitizeError::InvalidValue)
+        } else {
+            Ok(())
+        }
+    }
+}
 
 impl<T: BloomHashIndex> Bloom<T> {
     pub fn new(num_bits: usize, keys: Vec<u64>) -> Self {