Re: [LTP] [PATCH] syscalls/mmap04: Validate mapping perms in /proc/self/maps

[Cyril Hrubis <chrubis@suse.cz>]

Hi!
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (c) International Business Machines  Corp., 2001
> + *  07/2001 Ported by Wayne Boyer
> + * Copyright (c) 2023 SUSE LLC Avinesh Kumar <avinesh.kumar@suse.com>
> + */
> +
> +/*\
> + * [Description]
> + *
> + * Verify that, after a successful mmap() call, permission bits of the new
> + * mapping in /proc/pid/maps file matches the prot and flags arguments in
> + * mmap() call.
> + */
> +
> +#include "tst_test.h"
> +#include "tst_safe_stdio.h"
> +
> +#define MMAPSIZE 1024
> +static char *addr;
> +
> +static struct tcase {
> +	int prot;
> +	int flags;
> +	char *exp_perms;
> +} tcases[] = {
> +	{PROT_NONE, MAP_ANONYMOUS | MAP_PRIVATE, "---p"},
> +	{PROT_NONE, MAP_ANONYMOUS | MAP_SHARED, "---s"},
> +	{PROT_READ, MAP_ANONYMOUS | MAP_PRIVATE, "r--p"},
> +	{PROT_READ, MAP_ANONYMOUS | MAP_SHARED, "r--s"},
> +	{PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, "-w-p"},
> +	{PROT_WRITE, MAP_ANONYMOUS | MAP_SHARED, "-w-s"},
> +	{PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, "rw-p"},
> +	{PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_SHARED, "rw-s"},
> +	{PROT_READ | PROT_EXEC, MAP_ANONYMOUS | MAP_PRIVATE, "r-xp"},
> +	{PROT_READ | PROT_EXEC, MAP_ANONYMOUS | MAP_SHARED, "r-xs"},
> +	{PROT_WRITE | PROT_EXEC, MAP_ANONYMOUS | MAP_PRIVATE, "-wxp"},
> +	{PROT_WRITE | PROT_EXEC, MAP_ANONYMOUS | MAP_SHARED, "-wxs"},
> +	{PROT_READ | PROT_WRITE | PROT_EXEC, MAP_ANONYMOUS | MAP_PRIVATE, "rwxp"},
> +	{PROT_READ | PROT_WRITE | PROT_EXEC, MAP_ANONYMOUS | MAP_SHARED, "rwxs"}
> +};
> +
> +static void get_map_perms(char *addr_str, char *perms)
> +{
> +	FILE *file;
> +	char line[BUFSIZ];
> +
> +	file = SAFE_FOPEN("/proc/self/maps", "r");
> +
> +	while (fgets(line, sizeof(line), file)) {
> +		if (strstr(line, addr_str) != NULL) {
> +			if (sscanf(line, "%*x-%*x %s", perms) != 1)
> +				tst_brk(TBROK, "failed to find permission string in %s", line);
> +			break;
> +		}
> +	}
> +
> +	SAFE_FCLOSE(file);
> +	file = NULL;

No need to set the file to NULL here, it's on stack and will perish once
we leave this function.

Rather than that we should check that the perms was actually set at this
point. It's unlikely that it will be missing, but we are writing kernel
tests so we should really make sure we actually found it.

Also I do wonder if we can use SAFE_FILE_LINES_SCANF() here that would
sove the the problem since it will TBROK if the line wasn't found. For
that we would have to snprintf() the fmt string with the address so that
we pass something as "5560620ce000-%-x %s" to the scanf.

> +}
> +
> +static void run(unsigned int i)
> +{
> +	struct tcase *tc = &tcases[i];
> +	char addr_str[20];
> +	char perms[8];
> +
> +	addr = SAFE_MMAP(NULL, MMAPSIZE, tc->prot, tc->flags, -1, 0);
> +
> +	sprintf(addr_str, "%p", addr);
> +	if (sscanf(addr_str, "0x%s", addr_str) != 1)
> +		tst_brk(TBROK, "failed to find address string");

I guess that casting the address to (uintptr_t) and printing it with
"%"PRIxPTR is cleaner solution.

> +	get_map_perms(addr_str, perms);
> +
> +	if (!strcmp(perms, tc->exp_perms))
> +		tst_res(TPASS, "mapping permissions in /proc matched: %s", perms);
> +	else
> +		tst_res(TFAIL, "mapping permissions in /proc mismatched,"
> +						" expected: %s, found: %s",
> +						tc->exp_perms, perms);
> +
> +	SAFE_MUNMAP(addr, MMAPSIZE);
> +}
> +
> +static struct tst_test test = {
> +	.test = run,
> +	.tcnt = ARRAY_SIZE(tcases),
> +};
> -- 
> 2.41.0
> 
> 
> -- 
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-- 
Cyril Hrubis
chrubis@suse.cz

-- 
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