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 <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

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);