Patch "bpf, samples: Fix xdpsock with '-M' parameter missing unload process" has been added to the 5.13-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    bpf, samples: Fix xdpsock with '-M' parameter missing unload process

to the 5.13-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     bpf-samples-fix-xdpsock-with-m-parameter-missing-unl.patch
and it can be found in the queue-5.13 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 854b37b81b47443208c75ba7c3775fd49d335344
Author: Wang Hai <wanghai38@xxxxxxxxxx>
Date:   Mon Jun 28 17:18:15 2021 +0800

    bpf, samples: Fix xdpsock with '-M' parameter missing unload process
    
    [ Upstream commit 2620e92ae6ed83260eb46d214554cd308ee35d92 ]
    
    Execute the following command and exit, then execute it again, the following
    error will be reported:
    
      $ sudo ./samples/bpf/xdpsock -i ens4f2 -M
      ^C
      $ sudo ./samples/bpf/xdpsock -i ens4f2 -M
      libbpf: elf: skipping unrecognized data section(16) .eh_frame
      libbpf: elf: skipping relo section(17) .rel.eh_frame for section(16) .eh_frame
      libbpf: Kernel error message: XDP program already attached
      ERROR: link set xdp fd failed
    
    Commit c9d27c9e8dc7 ("samples: bpf: Do not unload prog within xdpsock") removed
    the unloading prog code because of the presence of bpf_link. This is fine if
    XDP_SHARED_UMEM is disabled, but if it is enabled, unloading the prog is still
    needed.
    
    Fixes: c9d27c9e8dc7 ("samples: bpf: Do not unload prog within xdpsock")
    Signed-off-by: Wang Hai <wanghai38@xxxxxxxxxx>
    Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
    Acked-by: Magnus Karlsson <magnus.karlsson@xxxxxxxxx>
    Cc: Maciej Fijalkowski <maciej.fijalkowski@xxxxxxxxx>
    Link: https://lore.kernel.org/bpf/20210628091815.2373487-1-wanghai38@xxxxxxxxxx
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/samples/bpf/xdpsock_user.c b/samples/bpf/xdpsock_user.c
index 53e300f860bb..33d0bdebbed8 100644
--- a/samples/bpf/xdpsock_user.c
+++ b/samples/bpf/xdpsock_user.c
@@ -96,6 +96,7 @@ static int opt_xsk_frame_size = XSK_UMEM__DEFAULT_FRAME_SIZE;
 static int opt_timeout = 1000;
 static bool opt_need_wakeup = true;
 static u32 opt_num_xsks = 1;
+static u32 prog_id;
 static bool opt_busy_poll;
 static bool opt_reduced_cap;
 
@@ -461,6 +462,23 @@ static void *poller(void *arg)
 	return NULL;
 }
 
+static void remove_xdp_program(void)
+{
+	u32 curr_prog_id = 0;
+
+	if (bpf_get_link_xdp_id(opt_ifindex, &curr_prog_id, opt_xdp_flags)) {
+		printf("bpf_get_link_xdp_id failed\n");
+		exit(EXIT_FAILURE);
+	}
+
+	if (prog_id == curr_prog_id)
+		bpf_set_link_xdp_fd(opt_ifindex, -1, opt_xdp_flags);
+	else if (!curr_prog_id)
+		printf("couldn't find a prog id on a given interface\n");
+	else
+		printf("program on interface changed, not removing\n");
+}
+
 static void int_exit(int sig)
 {
 	benchmark_done = true;
@@ -471,6 +489,9 @@ static void __exit_with_error(int error, const char *file, const char *func,
 {
 	fprintf(stderr, "%s:%s:%i: errno: %d/\"%s\"\n", file, func,
 		line, error, strerror(error));
+
+	if (opt_num_xsks > 1)
+		remove_xdp_program();
 	exit(EXIT_FAILURE);
 }
 
@@ -490,6 +511,9 @@ static void xdpsock_cleanup(void)
 		if (write(sock, &cmd, sizeof(int)) < 0)
 			exit_with_error(errno);
 	}
+
+	if (opt_num_xsks > 1)
+		remove_xdp_program();
 }
 
 static void swap_mac_addresses(void *data)
@@ -857,6 +881,10 @@ static struct xsk_socket_info *xsk_configure_socket(struct xsk_umem_info *umem,
 	if (ret)
 		exit_with_error(-ret);
 
+	ret = bpf_get_link_xdp_id(opt_ifindex, &prog_id, opt_xdp_flags);
+	if (ret)
+		exit_with_error(-ret);
+
 	xsk->app_stats.rx_empty_polls = 0;
 	xsk->app_stats.fill_fail_polls = 0;
 	xsk->app_stats.copy_tx_sendtos = 0;