Commit 611fbeb4 authored by Al Viro's avatar Al Viro Committed by Shuah Khan
Browse files

selftests:core: test coverage for dup_fd() failure handling in unshare_fd() 



At some point there'd been a dumb braino during the dup_fd()
calling conventions change; caught by smatch and immediately fixed.
The trouble is, there had been no test coverage for the dup_fd() failure
handling - neither in kselftests nor in LTP.  Fortunately, it can be
triggered on stock kernel - ENOMEM would require fault injection, but
EMFILE can be had with sysctl alone (fs.nr_open).

Add a test for dup_fd() failure.
Fixed up commit log and short log - Shuah Khan

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarShuah Khan <skhan@linuxfoundation.org>
parent c049acee

tools/testing/selftests/core/Makefile

+1 −1
Original line number Diff line number Diff line 
# SPDX-License-Identifier: GPL-2.0-only

CFLAGS += -g $(KHDR_INCLUDES)



TEST_GEN_PROGS := close_range_test

TEST_GEN_PROGS := close_range_test unshare_test



include ../lib.mk

tools/testing/selftests/core/unshare_test.c

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+94 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0



#define _GNU_SOURCE

#include <errno.h>

#include <fcntl.h>

#include <linux/kernel.h>

#include <limits.h>

#include <stdbool.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <syscall.h>

#include <unistd.h>

#include <sys/resource.h>

#include <linux/close_range.h>



#include "../kselftest_harness.h"

#include "../clone3/clone3_selftests.h"



TEST(unshare_EMFILE)

{

	pid_t pid;

	int status;

	struct __clone_args args = {

		.flags = CLONE_FILES,

		.exit_signal = SIGCHLD,

	};

	int fd;

	ssize_t n, n2;

	static char buf[512], buf2[512];

	struct rlimit rlimit;

	int nr_open;



	fd = open("/proc/sys/fs/nr_open", O_RDWR);

	ASSERT_GE(fd, 0);



	n = read(fd, buf, sizeof(buf));

	ASSERT_GT(n, 0);

	ASSERT_EQ(buf[n - 1], '\n');



	ASSERT_EQ(sscanf(buf, "%d", &nr_open), 1);



	ASSERT_EQ(0, getrlimit(RLIMIT_NOFILE, &rlimit));



	/* bump fs.nr_open */

	n2 = sprintf(buf2, "%d\n", nr_open + 1024);

	lseek(fd, 0, SEEK_SET);

	write(fd, buf2, n2);



	/* bump ulimit -n */

	rlimit.rlim_cur = nr_open + 1024;

	rlimit.rlim_max = nr_open + 1024;

	EXPECT_EQ(0, setrlimit(RLIMIT_NOFILE, &rlimit)) {

		lseek(fd, 0, SEEK_SET);

		write(fd, buf, n);

		exit(EXIT_FAILURE);

	}



	/* get a descriptor past the old fs.nr_open */

	EXPECT_GE(dup2(2, nr_open + 64), 0) {

		lseek(fd, 0, SEEK_SET);

		write(fd, buf, n);

		exit(EXIT_FAILURE);

	}



	/* get descriptor table shared */

	pid = sys_clone3(&args, sizeof(args));

	EXPECT_GE(pid, 0) {

		lseek(fd, 0, SEEK_SET);

		write(fd, buf, n);

		exit(EXIT_FAILURE);

	}



	if (pid == 0) {

		int err;



		/* restore fs.nr_open */

		lseek(fd, 0, SEEK_SET);

		write(fd, buf, n);

		/* ... and now unshare(CLONE_FILES) must fail with EMFILE */

		err = unshare(CLONE_FILES);

		EXPECT_EQ(err, -1)

			exit(EXIT_FAILURE);

		EXPECT_EQ(errno, EMFILE)

			exit(EXIT_FAILURE);

		exit(EXIT_SUCCESS);

	}



	EXPECT_EQ(waitpid(pid, &status, 0), pid);

	EXPECT_EQ(true, WIFEXITED(status));

	EXPECT_EQ(0, WEXITSTATUS(status));

}



TEST_HARNESS_MAIN