libxdp: Fix xdp prog memory leak in xsk_setup_xdp_prog

[ricmli]

In the xsk_setup_xdp_prog function, the xsk structure temporarily takes ownership of an xdp_prog and stores it in ctx->xdp_prog. However, the allocated xdp_prog is not freed in xsk_destroy_xsk_struct, leading to a memory leak. This commit addresses the issue by adding a call to xdp_program__close to properly release the allocated xdp_prog memory.

[ricmli]

Reproduction Steps:

We have two processes involved: Process 1, a privileged process, and Process 2, an unprivileged process.

• Process 1:

  • Loads and attaches our xdp object file using xdp_program__open_file and xdp_program__attach, or takes no action.
  • Calls xsk_setup_xdp_prog to obtain the xsks_map_fd.
  • When exit, detach and close the prog we opened, also detach and close the multiprog.

• Process 2:

  • Follows the standard AF_XDP routine, except for setting the XSK_LIBXDP_FLAGS__INHIBIT_PROG_LOAD, obtains the xsks_map_fd from Process 1 via a unix domain socket and updates the socket fd to xsks_map.

Example Output from AddressSanitizer for Process 1:

=================================================================
==702507==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 208 byte(s) in 2 object(s) allocated from:
    #0 0x7f85fa8b4a57 in __interceptor_calloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:154
    #1 0x7f85fb391a5b in xdp_program__new /home/media/ric/ricmli/xdp-tools/lib/libxdp/libxdp.c:1112
    #2 0x7f85fb391a5b in xdp_program__create_from_obj /home/media/ric/ricmli/xdp-tools/lib/libxdp/libxdp.c:1174

...

SUMMARY: AddressSanitizer: 10688 byte(s) leaked in 40 allocation(s).

[tohojo]

Thank you for the fix! :)