BUG/MINOR: stats: fix segfault caused by uninitialized value in "show schema json"

Since b3d5708 ("MINOR: stats: remove implicit static trash_chunk usage")
a segfault can occur when issuing "show schema json" on the stats socket.

Indeed, now the dumping functions don't rely on trash_chunk anymore, but
instead they rely on the appctx->chunk buffer. However, unlike other
stats dumping commands, the "show schema json" only have an io handler,
and no parse function. With other command, the parse function is
responsible for pre-setting some data, including applet ctx reservation.

Thus due to "show schema json" lacking parsing function, the applet ctx is
used uninitialized, which is a bug obviously.

To fix the issue we simply add a parse function for "show schema json",
although all it does for now is calling applet_reserve_svcctx() for the
current applet ctx.

This issue was reported by @dsuch in GH #2825. It must be backported up
to 3.0.

diff --git a/src/stats.c b/src/stats.c
index e1f33bd373d31984d79d56e49b39ddedc22d1e9e..1e5461b5b0b531ab72a11db4d484809d1d9ddc76 100644 (file)
--- a/src/stats.c
+++ b/src/stats.c
@@ -988,6 +988,14 @@ static int cli_parse_show_stat(char **args, char *payload, struct appctx *appctx
        return 0;
 }
 
+static int cli_parse_show_schema_json(char **args, char *payload, struct appctx *appctx, void *private)
+{
+       struct show_stat_ctx *ctx = applet_reserve_svcctx(appctx, sizeof(*ctx));
+
+       /* ctx is allocated, nothing else to do */
+       return 0;
+}
+
 static int cli_io_handler_dump_info(struct appctx *appctx)
 {
        struct show_stat_ctx *ctx = appctx->svcctx;
@@ -1315,7 +1323,7 @@ static struct cli_kw_list cli_kws = {{ },{
        { { "clear", "counters",  NULL },      "clear counters [all]                    : clear max statistics counters (or all counters)", cli_parse_clear_counters, NULL, NULL },
        { { "show", "info",  NULL },           "show info [desc|json|typed|float]*      : report information about the running process",    cli_parse_show_info, cli_io_handler_dump_info, NULL },
        { { "show", "stat",  NULL },           "show stat [desc|json|no-maint|typed|up]*: report counters for each proxy and server",       cli_parse_show_stat, cli_io_handler_dump_stat, cli_io_handler_release_stat },
-       { { "show", "schema",  "json", NULL }, "show schema json                        : report schema used for stats",                    NULL, cli_io_handler_dump_json_schema, NULL },
+       { { "show", "schema",  "json", NULL }, "show schema json                        : report schema used for stats",                    cli_parse_show_schema_json, cli_io_handler_dump_json_schema, NULL },
        { { "dump", "stats-file", NULL },      "dump stats-file                         : dump stats for restore",                          cli_parse_dump_stat_file, cli_io_handler_dump_stat_file, cli_io_handler_release_dump_stat_file },
        {{},}
 }};