[LTP] [PATCH] cve-2026-46331: fix intermittent ENOENT failure

[Cyril Hrubis]

Hi!
>  #include <sys/sendfile.h>
> +#include <sys/prctl.h>
> +#include <pwd.h>
>  #include <linux/rtnetlink.h>
>  
>  #include "tst_test.h"
> @@ -128,7 +130,31 @@ static int acc_fd = -1;
>  static void setup(void)
>  {
>  	struct sockaddr_in addr;
> -	int i;
> +	struct passwd *pw;
> +	static const char *const mods[] = {
> +		"sch_ingress", "cls_matchall", "act_pedit"
> +	};
> +	static const char *cmd[] = {"modprobe", NULL, NULL};
> +	unsigned int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(mods); i++) {
> +		cmd[1] = mods[i];
> +
> +		if (tst_cmd(cmd, NULL, "/dev/null", TST_CMD_PASS_RETVAL))
> +			tst_brk(TCONF, "kernel module %s is not available", mods[i]);
> +	}

We do have tst_module_load().

> +	/* Drop privileges so the reproducer runs as an unprivileged user */
> +	pw = SAFE_GETPWNAM("nobody");
> +	SAFE_SETGID(pw->pw_gid);
> +	SAFE_SETUID(pw->pw_uid);
> +
> +	/*
> +	 * setuid() clears the dumpable flag, which makes /proc/self/*
> +	 * owned by root and prevents tst_setup_netns() from writing the
> +	 * uid/gid maps. Restore it so the user namespace can be set up.
> +	 */
> +	SAFE_PRCTL(PR_SET_DUMPABLE, 1, 0, 0, 0);
>  
>  	tst_setup_netns();
>  	NETDEV_SET_STATE("lo", 1);
> @@ -253,7 +279,12 @@ static struct tst_test test = {
>  	.test_all = run,
>  	.setup = setup,
>  	.cleanup = cleanup,
> +	.needs_root = 1,
>  	.needs_tmpdir = 1,
> +	.needs_cmds = (struct tst_cmd[]) {
> +		{.cmd = "modprobe"},
> +		{}
> +	},
>  	.needs_kconfigs = (const char *[]) {
>  		"CONFIG_USER_NS=y",
>  		"CONFIG_NET_NS=y",

The check for the module existence should be done by adding:

	"CONFIG_NET_SCH_INGRESS",
	"CONFIG_NET_CLS_MATCHALL",
	"CONFIG_NET_ACT_PEDIT",

to the needs_kconfigs.

And then adding module mappings to tst_kconfig.c

	diff --git a/lib/tst_kconfig.c b/lib/tst_kconfig.c
index 44eacc7c2..277ac6068 100644
--- a/lib/tst_kconfig.c
+++ b/lib/tst_kconfig.c
@@ -162,6 +162,9 @@ static struct config_module_map {
        {"CONFIG_CAN_RAW", "can-raw"},
        {"CONFIG_CAN_BCM", "can-bcm"},
        {"CONFIG_IP_SCTP", "sctp"},
+       {"CONFIG_NET_SCH_INGRESS", "sch_ingress"},
+       {"CONFIG_NET_CLS_MATCHALL", "cls_matchall"},
+       {"CONFIG_NET_ACT_PEDIT", "act_pedit"},
        {}
 };


With that the checks will be done in the test library even before the
test is started.

We may also add a flag to tst_test structure to load the modules mapped
to the config variables, something as .kconfig_load.

-- 
Cyril Hrubis
chrubis@suse.cz