bpftool: Fix UAF in get_delegate_value

The return value ret pointer is pointing opts_copy, but opts_copy
gets freed in get_delegate_value before return, fix this by free
the mntent->mnt_opts strdup memory after show delegate value.

Fixes: 2d812311c2b2 ("bpftool: Add bpf_token show")
Signed-off-by: Tao Chen <chen.dylane@linux.dev>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Quentin Monnet <qmo@kernel.org>
Link: https://lore.kernel.org/bpf/20250919034816.1287280-2-chen.dylane@linux.dev

diff --git a/tools/bpf/bpftool/token.c b/tools/bpf/bpftool/token.c
index 82b829e44c82aa28c1efa5ca882faf32a40f5440..c08f34b9d51b580245c57eb13f3fb4ab12c6ac46 100644 (file)
--- a/tools/bpf/bpftool/token.c
+++ b/tools/bpf/bpftool/token.c
@@ -20,6 +20,16 @@
 
 #define MOUNTS_FILE "/proc/mounts"
 
+static struct {
+       const char *header;
+       const char *key;
+} sets[] = {
+       {"allowed_cmds", "delegate_cmds"},
+       {"allowed_maps", "delegate_maps"},
+       {"allowed_progs", "delegate_progs"},
+       {"allowed_attachs", "delegate_attachs"},
+};
+
 static bool has_delegate_options(const char *mnt_ops)
 {
        return strstr(mnt_ops, "delegate_cmds") ||
@@ -28,15 +38,14 @@ static bool has_delegate_options(const char *mnt_ops)
               strstr(mnt_ops, "delegate_attachs");
 }
 
-static char *get_delegate_value(const char *opts, const char *key)
+static char *get_delegate_value(char *opts, const char *key)
 {
        char *token, *rest, *ret = NULL;
-       char *opts_copy = strdup(opts);
 
-       if (!opts_copy)
+       if (!opts)
                return NULL;
 
-       for (token = strtok_r(opts_copy, ",", &rest); token;
+       for (token = strtok_r(opts, ",", &rest); token;
                        token = strtok_r(NULL, ",", &rest)) {
                if (strncmp(token, key, strlen(key)) == 0 &&
                    token[strlen(key)] == '=') {
@@ -44,24 +53,19 @@ static char *get_delegate_value(const char *opts, const char *key)
                        break;
                }
        }
-       free(opts_copy);
 
        return ret;
 }
 
-static void print_items_per_line(const char *input, int items_per_line)
+static void print_items_per_line(char *input, int items_per_line)
 {
-       char *str, *rest, *strs;
+       char *str, *rest;
        int cnt = 0;
 
        if (!input)
                return;
 
-       strs = strdup(input);
-       if (!strs)
-               return;
-
-       for (str = strtok_r(strs, ":", &rest); str;
+       for (str = strtok_r(input, ":", &rest); str;
                        str = strtok_r(NULL, ":", &rest)) {
                if (cnt % items_per_line == 0)
                        printf("\n\t  ");
@@ -69,38 +73,31 @@ static void print_items_per_line(const char *input, int items_per_line)
                printf("%-20s", str);
                cnt++;
        }
-
-       free(strs);
 }
 
 #define ITEMS_PER_LINE 4
 static void show_token_info_plain(struct mntent *mntent)
 {
-       char *value;
+       size_t i;
 
        printf("token_info  %s", mntent->mnt_dir);
 
-       printf("\n\tallowed_cmds:");
-       value = get_delegate_value(mntent->mnt_opts, "delegate_cmds");
-       print_items_per_line(value, ITEMS_PER_LINE);
-
-       printf("\n\tallowed_maps:");
-       value = get_delegate_value(mntent->mnt_opts, "delegate_maps");
-       print_items_per_line(value, ITEMS_PER_LINE);
+       for (i = 0; i < ARRAY_SIZE(sets); i++) {
+               char *opts, *value;
 
-       printf("\n\tallowed_progs:");
-       value = get_delegate_value(mntent->mnt_opts, "delegate_progs");
-       print_items_per_line(value, ITEMS_PER_LINE);
+               printf("\n\t%s:", sets[i].header);
+               opts = strdup(mntent->mnt_opts);
+               value = get_delegate_value(opts, sets[i].key);
+               print_items_per_line(value, ITEMS_PER_LINE);
+               free(opts);
+       }
 
-       printf("\n\tallowed_attachs:");
-       value = get_delegate_value(mntent->mnt_opts, "delegate_attachs");
-       print_items_per_line(value, ITEMS_PER_LINE);
        printf("\n");
 }
 
-static void split_json_array_str(const char *input)
+static void split_json_array_str(char *input)
 {
-       char *str, *rest, *strs;
+       char *str, *rest;
 
        if (!input) {
                jsonw_start_array(json_wtr);
@@ -108,43 +105,30 @@ static void split_json_array_str(const char *input)
                return;
        }
 
-       strs = strdup(input);
-       if (!strs)
-               return;
-
        jsonw_start_array(json_wtr);
-       for (str = strtok_r(strs, ":", &rest); str;
+       for (str = strtok_r(input, ":", &rest); str;
                        str = strtok_r(NULL, ":", &rest)) {
                jsonw_string(json_wtr, str);
        }
        jsonw_end_array(json_wtr);
-
-       free(strs);
 }
 
 static void show_token_info_json(struct mntent *mntent)
 {
-       char *value;
+       size_t i;
 
        jsonw_start_object(json_wtr);
-
        jsonw_string_field(json_wtr, "token_info", mntent->mnt_dir);
 
-       jsonw_name(json_wtr, "allowed_cmds");
-       value = get_delegate_value(mntent->mnt_opts, "delegate_cmds");
-       split_json_array_str(value);
+       for (i = 0; i < ARRAY_SIZE(sets); i++) {
+               char *opts, *value;
 
-       jsonw_name(json_wtr, "allowed_maps");
-       value = get_delegate_value(mntent->mnt_opts, "delegate_maps");
-       split_json_array_str(value);
-
-       jsonw_name(json_wtr, "allowed_progs");
-       value = get_delegate_value(mntent->mnt_opts, "delegate_progs");
-       split_json_array_str(value);
-
-       jsonw_name(json_wtr, "allowed_attachs");
-       value = get_delegate_value(mntent->mnt_opts, "delegate_attachs");
-       split_json_array_str(value);
+               jsonw_name(json_wtr, sets[i].header);
+               opts = strdup(mntent->mnt_opts);
+               value = get_delegate_value(opts, sets[i].key);
+               split_json_array_str(value);
+               free(opts);
+       }
 
        jsonw_end_object(json_wtr);
 }