Commit 0658a096 authored by Florian Weimer's avatar Florian Weimer Committed by Linus Torvalds
Browse files

procfs: do not list TID 0 in /proc/<pid>/task 

If a task exits concurrently, task_pid_nr_ns may return 0.

[akpm@linux-foundation.org: coding style tweaks]
[adobriyan@gmail.com: test that /proc/*/task doesn't contain "0"]
  Link: https://lkml.kernel.org/r/YV88AnVzHxPafQ9o@localhost.localdomain

Link: https://lkml.kernel.org/r/8735pn5dx7.fsf@oldenburg.str.redhat.com


Signed-off-by: default avatarFlorian Weimer <fweimer@redhat.com>
Signed-off-by: default avatarAlexey Dobriyan <adobriyan@gmail.com>
Acked-by: default avatarChristian Brauner <christian.brauner@ubuntu.com>
Reviewed-by: default avatarAlexey Dobriyan <adobriyan@gmail.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 83c1fd76

fs/proc/base.c

+3 −0
Original line number Diff line number Diff line
@@ -3799,7 +3799,10 @@ static int proc_task_readdir(struct file *file, struct dir_context *ctx) 
	     task = next_tid(task), ctx->pos++) {

		char name[10 + 1];

		unsigned int len;



		tid = task_pid_nr_ns(task, ns);

		if (!tid)

			continue;	/* The task has just exited. */

		len = snprintf(name, sizeof(name), "%u", tid);

		if (!proc_fill_cache(file, ctx, name, len,

				proc_task_instantiate, task, NULL)) {

tools/testing/selftests/proc/.gitignore

+1 −0
Original line number Diff line number Diff line
@@ -11,6 +11,7 @@ 
/proc-self-syscall

/proc-self-wchan

/proc-subset-pid

/proc-tid0

/proc-uptime-001

/proc-uptime-002

/read

tools/testing/selftests/proc/Makefile

+2 −0
Original line number Diff line number Diff line 
# SPDX-License-Identifier: GPL-2.0-only

CFLAGS += -Wall -O2 -Wno-unused-function

CFLAGS += -D_GNU_SOURCE

LDFLAGS += -pthread



TEST_GEN_PROGS :=

TEST_GEN_PROGS += fd-001-lookup
@@ -13,6 +14,7 @@ TEST_GEN_PROGS += proc-self-map-files-002 
TEST_GEN_PROGS += proc-self-syscall

TEST_GEN_PROGS += proc-self-wchan

TEST_GEN_PROGS += proc-subset-pid

TEST_GEN_PROGS += proc-tid0

TEST_GEN_PROGS += proc-uptime-001

TEST_GEN_PROGS += proc-uptime-002

TEST_GEN_PROGS += read

tools/testing/selftests/proc/proc-tid0.c

0 → 100644
+81 −0
Original line number Diff line number Diff line 
/*

 * Copyright (c) 2021 Alexey Dobriyan <adobriyan@gmail.com>

 *

 * Permission to use, copy, modify, and distribute this software for any

 * purpose with or without fee is hereby granted, provided that the above

 * copyright notice and this permission notice appear in all copies.

 *

 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES

 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF

 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR

 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES

 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN

 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF

 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

 */

// Test that /proc/*/task never contains "0".

#include <sys/types.h>

#include <dirent.h>

#include <signal.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <unistd.h>

#include <pthread.h>



static pid_t pid = -1;



static void atexit_hook(void)

{

	if (pid > 0) {

		kill(pid, SIGKILL);

	}

}



static void *f(void *_)

{

	return NULL;

}



static void sigalrm(int _)

{

	exit(0);

}



int main(void)

{

	pid = fork();

	if (pid == 0) {

		/* child */

		while (1) {

			pthread_t pth;

			pthread_create(&pth, NULL, f, NULL);

			pthread_join(pth, NULL);

		}

	} else if (pid > 0) {

		/* parent */

		atexit(atexit_hook);



		char buf[64];

		snprintf(buf, sizeof(buf), "/proc/%u/task", pid);



		signal(SIGALRM, sigalrm);

		alarm(1);



		while (1) {

			DIR *d = opendir(buf);

			struct dirent *de;

			while ((de = readdir(d))) {

				if (strcmp(de->d_name, "0") == 0) {

					exit(1);

				}

			}

			closedir(d);

		}



		return 0;

	} else {

		perror("fork");

		return 1;

	}

}