tools: bpftool: fix crash with un-owned prog arrays

Prog arrays don't have 'owner_prog_type' and 'owner_jited'
fields in their fdinfo when they are created.  Those fields
are set and reported when first program is checked for
compatibility by bpf_prog_array_compatible().

This means that bpftool cannot expect the fields to always
be there.  Currently trying to show maps on a system with
an un-owned prog array leads to a crash:

$ bpftool map show
389: prog_array  name tail_call_map  flags 0x0
Error: key 'owner_prog_type' not found in fdinfo
Error: key 'owner_jited' not found in fdinfo
       key 4B  value 4B  max_entries 4  memlock 4096B
       Segmentation fault (core dumped)

We pass a NULL pointer to atoi().

Remove the assumption that fdinfo keys are always present.
Add missing validations and remove the p_err() calls which
may lead to broken JSON output as caller will not propagate
the failure.

Fixes: 99a44be ("tools: bpftool: add owner_prog_type and owner_jited to bpftool output")
Signed-off-by: Jakub Kicinski <[email protected]>
Reviewed-by: Quentin Monnet <[email protected]>
Acked-by: Song Liu <[email protected]>
Signed-off-by: Daniel Borkmann <[email protected]>

Author: Jakub Kicinski

tools/bpf/bpftool/common.c

@@ -297,10 +297,8 @@ char *get_fdinfo(int fd, const char *key)
 	snprintf(path, sizeof(path), "/proc/self/fdinfo/%d", fd);
 
 	fdi = fopen(path, "r");
-	if (!fdi) {
-		p_err("can't open fdinfo: %s", strerror(errno));
+	if (!fdi)
 		return NULL;
-	}
 
 	while ((n = getline(&line, &line_n, fdi)) > 0) {
 		char *value;
@@ -313,7 +311,6 @@ char *get_fdinfo(int fd, const char *key)
 
 		value = strchr(line, '\t');
 		if (!value || !value[1]) {
-			p_err("malformed fdinfo!?");
 			free(line);
 			return NULL;
 		}
@@ -326,7 +323,6 @@ char *get_fdinfo(int fd, const char *key)
 		return line;
 	}
 
-	p_err("key '%s' not found in fdinfo", key);
 	free(line);
 	fclose(fdi);
 	return NULL;

tools/bpf/bpftool/map.c

@@ -513,10 +513,9 @@ static int show_map_close_json(int fd, struct bpf_map_info *info)
 				jsonw_uint_field(json_wtr, "owner_prog_type",
 						 prog_type);
 		}
-		if (atoi(owner_jited))
-			jsonw_bool_field(json_wtr, "owner_jited", true);
-		else
-			jsonw_bool_field(json_wtr, "owner_jited", false);
+		if (owner_jited)
+			jsonw_bool_field(json_wtr, "owner_jited",
+					 !!atoi(owner_jited));
 
 		free(owner_prog_type);
 		free(owner_jited);
@@ -569,7 +568,8 @@ static int show_map_close_plain(int fd, struct bpf_map_info *info)
 		char *owner_prog_type = get_fdinfo(fd, "owner_prog_type");
 		char *owner_jited = get_fdinfo(fd, "owner_jited");
 
-		printf("\n\t");
+		if (owner_prog_type || owner_jited)
+			printf("\n\t");
 		if (owner_prog_type) {
 			unsigned int prog_type = atoi(owner_prog_type);
 
@@ -579,10 +579,9 @@ static int show_map_close_plain(int fd, struct bpf_map_info *info)
 			else
 				printf("owner_prog_type %d  ", prog_type);
 		}
-		if (atoi(owner_jited))
-			printf("owner jited");
-		else
-			printf("owner not jited");
+		if (owner_jited)
+			printf("owner%s jited",
+			       atoi(owner_jited) ? "" : " not");
 
 		free(owner_prog_type);
 		free(owner_jited);