[LTP] [PATCH v2 4/7] Add lsm_get_self_attr03 test

[Cyril Hrubis]

Hi!
> index 0000000000000000000000000000000000000000..b432006650bff697eb60eb7ad6fdd62dbe0eb984
> --- /dev/null
> +++ b/testcases/kernel/syscalls/lsm/lsm_get_self_attr03.c
> @@ -0,0 +1,70 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (C) 2024 SUSE LLC Andrea Cervesato <andrea.cervesato@suse.com>
> + */
> +
> +/*\
> + * [Description]
> + *
> + * Verify that LSM_ATTR_CURRENT attribute is correctly recognizing
> + * the current, active security context of the process. This is done by
> + * checking that /proc/self/attr/current matches with the obtained value.
> + */
> +
> +#include "lsm_common.h"
> +
> +static struct lsm_ctx *ctx;
> +static uint32_t page_size;
> +
> +static void run(void)
> +{
> +	tst_res(TINFO, "Verifying 'LSM_ATTR_CURRENT' attribute");
> +
> +	uint32_t count;
> +	uint32_t size = page_size;
> +	char attr[size];
> +
> +	memset(attr, 0, size);
> +	memset(ctx, 0, sizeof(struct lsm_ctx));
> +
> +	count = TST_EXP_POSITIVE(
> +		lsm_get_self_attr(LSM_ATTR_CURRENT, ctx, &size, 0));
                                                          ^
							  This does not
							  look right.


Shouldn't we pass size initialized to size of the ctx->ctx[] there?

You are mixing the size of the attr[] array and the size of the ctx
into a single variable which isn't right at all. The attr[] size can
also be much smaller, since it's just a single string.

Looking back at the lapi/lsm.h the definition of the lsm_ctx structure
is wrong there too. You define the ctx[] as an array of 4096 bytes. That
is wrong because it does not match the system definition where it's
defined as a flexible array.

The correct solution is to:

1) change the ctx[4096] in the lapi/lsm.h to just ctx[]
   (so that we match the system definition)
2) define CTX_DATA_SIZE to something sensible, e.g. 4096
3) the size for allocation of the ctx must be sizeof(struct lsm_ctx) + CTX_DATA_SIZE
   (since the size passed to the syscall is the size of the ctx flexible array)
4) the size passed to the lsm_get_self_attr() must be then initialized to CTX_DATA_SIZE

-- 
Cyril Hrubis
chrubis@suse.cz