Fix set with duplicate elements causes sdiff to hang (#11530)

This payload produces a set with duplicate elements (listpack encoding):
```
restore _key 0 "\x14\x25\x25\x00\x00\x00\x0A\x00\x06\x01\x82\x5F\x35\x03\x04\x01\x82\x5F\x31\x03\x82\x5F\x33\x03\x00\x01\x82\x5F\x39\x03\x82\x5F\x33\x03\x08\x01\x02\x01\xFF\x0B\x00\x31\xBE\x7D\x41\x01\x03\x5B\xEC"

smembers key
1) "6"
2) "_5"
3) "4"
4) "_1"
5) "_3"  ---> dup
6) "0"
7) "_9"
8) "_3"  ---> dup
9) "8"
10) "2"
```

This kind of sets will cause SDIFF to hang, SDIFF generated a broken
protocol and left the client hung. (Expected ten elements, but only
got nine elements due to the duplication.)

If we set `sanitize-dump-payload` to yes, we will be able to find
the duplicate elements and report "ERR Bad data format".

Discovered and discussed in #11290.

This PR also improve prints when corrupt-dump-fuzzer hangs, it will
print the cmds and the payload, an example like:
```
Testing integration/corrupt-dump-fuzzer
[TIMEOUT]: clients state report follows.
sock6 => (SPAWNED SERVER) pid:28884
Killing still running Redis server 28884
commands caused test to hang:
SDIFF __key 
payload that caused test to hang: "\x14\balabala"
```

Co-authored-by: Oran Agra <oran@redislabs.com>

src/t_set.c

@@ -1493,8 +1493,7 @@ void sunionDiffGenericCommand(client *c, robj **setkeys, int setnum,
             }
             if (j == setnum) {
                 /* There is no other set with this element. Add it. */
-                setTypeAddAux(dstset, str, len, llval, encoding == OBJ_ENCODING_HT);
+                cardinality += setTypeAddAux(dstset, str, len, llval, encoding == OBJ_ENCODING_HT);
-                cardinality++;
             }
         }
         setTypeReleaseIterator(si);

tests/integration/corrupt-dump-fuzzer.tcl

@@ -147,10 +147,21 @@ foreach sanitize_dump {no yes} {
                         if {$dbsize != [r dbsize]} {
                             puts "unexpected keys"
                             puts "keys: [r keys *]"
-                            puts $sent
+                            puts "commands leading to it:"
+                            foreach cmd $sent {
+                                foreach arg $cmd {
+                                    puts -nonewline "[string2printable $arg] "
+                                }
+                                puts ""
+                            }
                             exit 1
                         }
                     } err ] } {
+                        set err [format "%s" $err] ;# convert to string for pattern matching
+                        if {[string match "*SIGTERM*" $err]} {
+                            puts "payload that caused test to hang: $printable_dump"
+                            exit 1
+                        }
                         # if the server terminated update stats and restart it
                         set report_and_restart true
                         incr stat_terminated_in_traffic

tests/integration/corrupt-dump.tcl

@@ -810,5 +810,24 @@ test {corrupt payload: fuzzer findings - empty set listpack} {
     }
 }
 
+test {corrupt payload: fuzzer findings - set with duplicate elements causes sdiff to hang} {
+    start_server [list overrides [list loglevel verbose use-exit-on-panic yes crash-memcheck-enabled no] ] {
+        r config set sanitize-dump-payload yes
+        r debug set-skip-checksum-validation 1
+        catch {r restore _key 0 "\x14\x25\x25\x00\x00\x00\x0A\x00\x06\x01\x82\x5F\x35\x03\x04\x01\x82\x5F\x31\x03\x82\x5F\x33\x03\x00\x01\x82\x5F\x39\x03\x82\x5F\x33\x03\x08\x01\x02\x01\xFF\x0B\x00\x31\xBE\x7D\x41\x01\x03\x5B\xEC" replace} err
+        assert_match "*Bad data format*" $err
+        r ping
+
+        # In the past, it generated a broken protocol and left the client hung in sdiff
+        r config set sanitize-dump-payload no
+        assert_equal {OK} [r restore _key 0 "\x14\x25\x25\x00\x00\x00\x0A\x00\x06\x01\x82\x5F\x35\x03\x04\x01\x82\x5F\x31\x03\x82\x5F\x33\x03\x00\x01\x82\x5F\x39\x03\x82\x5F\x33\x03\x08\x01\x02\x01\xFF\x0B\x00\x31\xBE\x7D\x41\x01\x03\x5B\xEC" replace]
+        assert_type set _key
+        assert_encoding listpack _key
+        assert_equal 10 [r scard _key]
+        assert_equal {0 2 4 6 8 _1 _3 _3 _5 _9} [lsort [r smembers _key]]
+        assert_equal {0 2 4 6 8 _1 _3 _5 _9} [lsort [r sdiff _key]]
+    }
+}
+
 } ;# tags
 

tests/support/util.tcl

@@ -730,13 +730,20 @@ proc generate_fuzzy_traffic_on_key {key duration} {
         } else {
             set err [format "%s" $err] ;# convert to string for pattern matching
             if {[string match "*SIGTERM*" $err]} {
-                puts "command caused test to hang? $cmd"
+                puts "commands caused test to hang:"
-                exit 1
+                foreach cmd $sent {
+                    foreach arg $cmd {
+                        puts -nonewline "[string2printable $arg] "
+                    }
+                    puts ""
+                }
+                # Re-raise, let handler up the stack take care of this.
+                error $err $::errorInfo
             }
         }
     }
 
-    # print stats so that we know if we managed to generate commands that actually made senes
+    # print stats so that we know if we managed to generate commands that actually made sense
     #if {$::verbose} {
     #    set count [llength $sent]
     #    puts "Fuzzy traffic sent: $count, succeeded: $succeeded"