[jira] [Created] (YARN-9420) Avoid potentially dangerous filename concatenation in native code (cgroups-operations.c)

["Szilard Nemeth (JIRA)" <ji...@apache.org>]

Szilard Nemeth created YARN-9420:
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             Summary: Avoid potentially dangerous filename concatenation in native code (cgroups-operations.c)
                 Key: YARN-9420
                 URL: https://issues.apache.org/jira/browse/YARN-9420
             Project: Hadoop YARN
          Issue Type: Improvement
            Reporter: Szilard Nemeth


In cgroups-operations.c, in function get_cgroups_path_to_write, at the end of the function, there's a string formatting operation:
{code:java}
if (snprintf(buffer, MAX_PATH_LEN, "%s/%s/%s/%s/%s.%s",
 cgroups_root, hierarchy_name, yarn_hierarchy_name,
 group_id, hierarchy_name, param_name) < 0) {
 fprintf(ERRORFILE, "Failed to print output path.\n");
 failed = 1;
 goto cleanup;
 }{code}

This functions is being called from just one function: update_cgroups_parameters
All calls of update_cgroups_parameters look like this (note that only the last parameter differs):
{code:java}
update_cgroups_parameters_func_p("devices", "deny",
 container_id, param_value);{code}
So essentially, get_cgroups_path_to_write will have these arguments:
1. hierarchy_name: "devices"
2. param_name: "allow"
3. group_id: container_id

An example of a full path:
{code:java}
/var/lib/yarn-ce/cgroups/devices/hadoop-yarn/c_1/devices.deny{code}
, where: 
1. cgroups_root = "/var/lib/yarn-ce/cgroups"
2. hierarchy_name = "devices"
3. yarn_hierarchy_name = "/hadoop-yarn"
4. group_id = "c_1"
5. param_name = "deny"

The problem is that the last bit of the format string ("%s.%s") relies on the fact that the variable hierarchy_name holds the value "devices", so it can be reused in the path and for the filename as well ("devices.deny").
It would be more clear if param_name would hold the whole filename as is, e.g. "devices.allow", instead of manually constructing it from 2 strings.



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