Fix memory leak with CLIENT LIST/KILL duplicate filters (#2362)

With #1401, we introduced additional filters to CLIENT LIST/KILL
subcommand. The intended behavior was to pick the last value of the
filter. However, we introduced memory leak for all the preceding
filters.

Before this change:
```
> CLIENT LIST IP 127.0.0.1 IP 127.0.0.1
id=4 addr=127.0.0.1:37866 laddr=127.0.0.1:6379 fd=10 name= age=0 idle=0 flags=N capa= db=0 sub=0 psub=0 ssub=0 multi=-1 watch=0 qbuf=0 qbuf-free=0 argv-mem=21 multi-mem=0 rbs=16384 rbp=16384 obl=0 oll=0 omem=0 tot-mem=16989 events=r cmd=client|list user=default redir=-1 resp=2 lib-name= lib-ver= tot-net-in=49 tot-net-out=0 tot-cmds=0
```
Leak:
```
Direct leak of 11 byte(s) in 1 object(s) allocated from:
    #0 0x7f2901aa557d in malloc (/lib64/libasan.so.4+0xd857d)
    #1 0x76db76 in ztrymalloc_usable_internal /workplace/harkrisp/valkey/src/zmalloc.c:156
    #2 0x76db76 in zmalloc_usable /workplace/harkrisp/valkey/src/zmalloc.c:200
    #3 0x4c4121 in _sdsnewlen.constprop.230 /workplace/harkrisp/valkey/src/sds.c:113
    #4 0x4dc456 in parseClientFiltersOrReply.constprop.63 /workplace/harkrisp/valkey/src/networking.c:4264
    #5 0x4bb9f7 in clientListCommand /workplace/harkrisp/valkey/src/networking.c:4600
    #6 0x641159 in call /workplace/harkrisp/valkey/src/server.c:3772
    #7 0x6431a6 in processCommand /workplace/harkrisp/valkey/src/server.c:4434
    #8 0x4bfa9b in processCommandAndResetClient /workplace/harkrisp/valkey/src/networking.c:3571
    #9 0x4bfa9b in processInputBuffer /workplace/harkrisp/valkey/src/networking.c:3702
    #10 0x4bffa3 in readQueryFromClient /workplace/harkrisp/valkey/src/networking.c:3812
    #11 0x481015 in callHandler /workplace/harkrisp/valkey/src/connhelpers.h:79
    #12 0x481015 in connSocketEventHandler.lto_priv.394 /workplace/harkrisp/valkey/src/socket.c:301
    #13 0x7d3fb3 in aeProcessEvents /workplace/harkrisp/valkey/src/ae.c:486
    #14 0x7d4d44 in aeMain /workplace/harkrisp/valkey/src/ae.c:543
    #15 0x453925 in main /workplace/harkrisp/valkey/src/server.c:7319
    #16 0x7f2900cd7139 in __libc_start_main (/lib64/libc.so.6+0x21139)
```

Note: For filter ID / NOT-ID we group all the option and perform
filtering whereas for remaining filters we only pick the last filter
option.

---------

Signed-off-by: Harkrishn Patro <[email protected]>

Author: hpatro

src/networking.c

@@ -4577,13 +4577,21 @@ static int parseClientFiltersOrReply(client *c, int index, clientFilter *filter)
             filter->idle = idle_time;
             index += 2;
         } else if (!strcasecmp(c->argv[index]->ptr, "flags") && moreargs) {
+            if (filter->flags) {
+                sdsfree(filter->flags);
+                filter->flags = NULL;
+            }
             filter->flags = sdsnew(c->argv[index + 1]->ptr);
             if (validateClientFlagFilter(filter->flags) == C_ERR) {
                 addReplyErrorFormat(c, "Unknown flags found in the provided filter: %s", filter->flags);
                 return C_ERR;
             }
             index += 2;
         } else if (!strcasecmp(c->argv[index]->ptr, "not-flags") && moreargs) {
+            if (filter->not_flags) {
+                sdsfree(filter->not_flags);
+                filter->not_flags = NULL;
+            }
             filter->not_flags = sdsnew(c->argv[index + 1]->ptr);
             if (validateClientFlagFilter(filter->not_flags) == C_ERR) {
                 addReplyErrorFormat(c, "Unknown flags found in the NOT-FLAGS filter: %s", filter->not_flags);
@@ -4597,18 +4605,34 @@ static int parseClientFiltersOrReply(client *c, int index, clientFilter *filter)
             filter->not_name = c->argv[index + 1]->ptr;
             index += 2;
         } else if (!strcasecmp(c->argv[index]->ptr, "lib-name") && moreargs) {
+            if (filter->lib_name) {
+                decrRefCount(filter->lib_name);
+                filter->lib_name = NULL;
+            }
             filter->lib_name = c->argv[index + 1];
             incrRefCount(filter->lib_name);
             index += 2;
         } else if (!strcasecmp(c->argv[index]->ptr, "not-lib-name") && moreargs) {
+            if (filter->not_lib_name) {
+                decrRefCount(filter->not_lib_name);
+                filter->not_lib_name = NULL;
+            }
             filter->not_lib_name = c->argv[index + 1];
             incrRefCount(filter->not_lib_name);
             index += 2;
         } else if (!strcasecmp(c->argv[index]->ptr, "lib-ver") && moreargs) {
+            if (filter->lib_ver) {
+                decrRefCount(filter->lib_ver);
+                filter->lib_ver = NULL;
+            }
             filter->lib_ver = c->argv[index + 1];
             incrRefCount(filter->lib_ver);
             index += 2;
         } else if (!strcasecmp(c->argv[index]->ptr, "not-lib-ver") && moreargs) {
+            if (filter->not_lib_ver) {
+                decrRefCount(filter->not_lib_ver);
+                filter->not_lib_ver = NULL;
+            }
             filter->not_lib_ver = c->argv[index + 1];
             incrRefCount(filter->not_lib_ver);
             index += 2;
@@ -4635,23 +4659,39 @@ static int parseClientFiltersOrReply(client *c, int index, clientFilter *filter)
             filter->not_db_number = not_db_id;
             index += 2;
         } else if (!strcasecmp(c->argv[index]->ptr, "capa") && moreargs) {
+            if (filter->capa) {
+                sdsfree(filter->capa);
+                filter->capa = NULL;
+            }
             filter->capa = sdsnew(c->argv[index + 1]->ptr);
             if (validateClientCapaFilter(filter->capa) == C_ERR) {
                 addReplyErrorFormat(c, "Unknown capa found in the provided filter: %s", filter->capa);
                 return C_ERR;
             }
             index += 2;
         } else if (!strcasecmp(c->argv[index]->ptr, "not-capa") && moreargs) {
+            if (filter->not_capa) {
+                sdsfree(filter->not_capa);
+                filter->not_capa = NULL;
+            }
             filter->not_capa = sdsnew(c->argv[index + 1]->ptr);
             if (validateClientCapaFilter(filter->not_capa) == C_ERR) {
                 addReplyErrorFormat(c, "Unknown capa found in the NOT-CAPA filter: %s", filter->not_capa);
                 return C_ERR;
             }
             index += 2;
         } else if (!strcasecmp(c->argv[index]->ptr, "ip") && moreargs) {
+            if (filter->ip) {
+                sdsfree(filter->ip);
+                filter->ip = NULL;
+            }
             filter->ip = sdsnew(c->argv[index + 1]->ptr);
             index += 2;
         } else if (!strcasecmp(c->argv[index]->ptr, "not-ip") && moreargs) {
+            if (filter->not_ip) {
+                sdsfree(filter->not_ip);
+                filter->not_ip = NULL;
+            }
             filter->not_ip = sdsnew(c->argv[index + 1]->ptr);
             index += 2;
         } else {
@@ -5016,6 +5056,7 @@ void clientListCommand(client *c) {
         filter.not_type = -1;
         filter.db_number = -1;
         filter.not_db_number = -1;
+
         int i = 2;
 
         if (parseClientFiltersOrReply(c, i, &filter) != C_OK) {