From 9f13b2bd4967334b1701c6eccdf53760cb13f79e Mon Sep 17 00:00:00 2001
From: John Sully <john@csquare.ca>
Date: Thu, 14 Mar 2019 14:02:16 -0400
Subject: [PATCH] Fix hyperloglog corruption

---
 src/hyperloglog.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/hyperloglog.c b/src/hyperloglog.c
index fc21ea0065d..e993bf26e1d 100644
--- a/src/hyperloglog.c
+++ b/src/hyperloglog.c
@@ -614,6 +614,10 @@ int hllSparseToDense(robj *o) {
         } else {
             runlen = HLL_SPARSE_VAL_LEN(p);
             regval = HLL_SPARSE_VAL_VALUE(p);
+            if ((runlen + idx) > HLL_REGISTERS) {
+                sdsfree(dense);
+                return C_ERR;
+            }
             while(runlen--) {
                 HLL_DENSE_SET_REGISTER(hdr->registers,idx,regval);
                 idx++;
@@ -1088,6 +1092,8 @@ int hllMerge(uint8_t *max, robj *hll) {
             } else {
                 runlen = HLL_SPARSE_VAL_LEN(p);
                 regval = HLL_SPARSE_VAL_VALUE(p);
+                if ((runlen + i) > HLL_REGISTERS)
+                    return C_ERR;
                 while(runlen--) {
                     if (regval > max[i]) max[i] = regval;
                     i++;
From e216ceaf0e099536fe3658a29dcb725d812364e0 Mon Sep 17 00:00:00 2001
From: antirez <antirez@gmail.com>
Date: Fri, 15 Mar 2019 17:16:06 +0100
Subject: [PATCH] HyperLogLog: handle wrong offset in the base case.

---
 src/hyperloglog.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/src/hyperloglog.c b/src/hyperloglog.c
index 526510b43b9..1e7ce3dceb7 100644
--- a/src/hyperloglog.c
+++ b/src/hyperloglog.c
@@ -614,10 +614,7 @@ int hllSparseToDense(robj *o) {
         } else {
             runlen = HLL_SPARSE_VAL_LEN(p);
             regval = HLL_SPARSE_VAL_VALUE(p);
-            if ((runlen + idx) > HLL_REGISTERS) {
-                sdsfree(dense);
-                return C_ERR;
-            }
+            if ((runlen + idx) > HLL_REGISTERS) break; /* Overflow. */
             while(runlen--) {
                 HLL_DENSE_SET_REGISTER(hdr->registers,idx,regval);
                 idx++;
@@ -1097,8 +1094,7 @@ int hllMerge(uint8_t *max, robj *hll) {
             } else {
                 runlen = HLL_SPARSE_VAL_LEN(p);
                 regval = HLL_SPARSE_VAL_VALUE(p);
-                if ((runlen + i) > HLL_REGISTERS)
-                    return C_ERR;
+                if ((runlen + i) > HLL_REGISTERS) break; /* Overflow. */
                 while(runlen--) {
                     if (regval > max[i]) max[i] = regval;
                     i++;
From 4208666797b5831eefc022ae46ab5747200cd671 Mon Sep 17 00:00:00 2001
From: antirez <antirez@gmail.com>
Date: Fri, 15 Mar 2019 13:52:29 +0100
Subject: [PATCH] HyperLogLog: dense/sparse repr parsing fuzz test.

---
 tests/unit/hyperloglog.tcl | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/tests/unit/hyperloglog.tcl b/tests/unit/hyperloglog.tcl
index 7d36b7a351f..6a9c47b11c5 100644
--- a/tests/unit/hyperloglog.tcl
+++ b/tests/unit/hyperloglog.tcl
@@ -115,6 +115,35 @@ start_server {tags {"hll"}} {
         set e
     } {*WRONGTYPE*}
 
+    test {Fuzzing dense/sparse encoding: Redis should always detect errors} {
+        for {set j 0} {$j < 10000} {incr j} {
+            r del hll
+            set items {}
+            set numitems [randomInt 3000]
+            for {set i 0} {$i < $numitems} {incr i} {
+                lappend items [expr {rand()}]
+            }
+            r pfadd hll {*}$items
+
+            # Corrupt it in some random way.
+            for {set i 0} {$i < 5} {incr i} {
+                set len [r strlen hll]
+                set pos [randomInt $len]
+                set byte [randstring 1 1 binary]
+                r setrange hll $pos $byte
+                # Don't modify more bytes 50% of times
+                if {rand() < 0.5} break
+            }
+
+            # Use the hyperloglog to check if it crashes
+            # Redis in some way.
+            catch {
+                r pfcount hll
+                r pfdebug getreg hll
+            }
+        }
+    }
+
     test {PFADD, PFCOUNT, PFMERGE type checking works} {
         r set foo bar
         catch {r pfadd foo 1} e