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fusefs: fix a race condition in the allow_other test

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The test could occasionally hang if the parent's SIGUSR2 signal arrived
before the child had pause()d.  Using POSIX semaphores precludes that
possibility.

Sponsored by:	The FreeBSD Foundation
This commit is contained in:
Alan Somers 2019-03-27 00:24:57 +00:00
parent fd2749f25d
commit 13eaa5fadc
1 changed files with 21 additions and 9 deletions
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30
tests/sys/fs/fusefs/allow_other.cc
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@ -35,10 +35,11 @@
extern "C" {
#include <sys/types.h>
#include <sys/mman.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <pwd.h>
#include <signal.h>
#include <semaphore.h>
}
#include "mockfs.hh"
@ -101,12 +102,17 @@ TEST_F(AllowOther, allowed)
uint64_t ino = 42;
int fd;
pid_t child;
sem_t *sem;
int mprot = PROT_READ | PROT_WRITE;
int mflags = MAP_ANON | MAP_SHARED;
signal(SIGUSR2, sighandler);
sem = (sem_t*)mmap(NULL, sizeof(*sem), mprot, mflags, -1, 0);
ASSERT_NE(NULL, sem) << strerror(errno);
ASSERT_EQ(0, sem_init(sem, 1, 0)) << strerror(errno);
if ((child = fork()) == 0) {
/* In child */
pause();
ASSERT_EQ(0, sem_wait(sem)) << strerror(errno);
/* Drop privileges before accessing */
if (0 != setreuid(-1, m_uid)) {
@ -122,6 +128,8 @@ TEST_F(AllowOther, allowed)
/* Deliberately leak fd */
} else if (child > 0) {
int child_status;
/*
* In parent. Cleanup must happen here, because it's still
* privileged.
@ -134,8 +142,7 @@ TEST_F(AllowOther, allowed)
expect_getattr(ino, 0);
m_mock->m_child_pid = child;
/* Signal the child process to go */
kill(child, SIGUSR2);
int child_status;
ASSERT_EQ(0, sem_post(sem)) << strerror(errno);
wait(&child_status);
ASSERT_EQ(0, WEXITSTATUS(child_status));
@ -149,12 +156,17 @@ TEST_F(NoAllowOther, disallowed)
const char FULLPATH[] = "mountpoint/some_file.txt";
int fd;
pid_t child;
signal(SIGUSR2, sighandler);
sem_t *sem;
int mprot = PROT_READ | PROT_WRITE;
int mflags = MAP_ANON | MAP_SHARED;
sem = (sem_t*)mmap(NULL, sizeof(*sem), mprot, mflags, -1, 0);
ASSERT_NE(NULL, sem) << strerror(errno);
ASSERT_EQ(0, sem_init(sem, 1, 0)) << strerror(errno);
if ((child = fork()) == 0) {
/* In child */
pause();
ASSERT_EQ(0, sem_wait(sem)) << strerror(errno);
/* Drop privileges before accessing */
if (0 != setreuid(-1, m_uid)) {
@ -180,7 +192,7 @@ TEST_F(NoAllowOther, disallowed)
*/
m_mock->m_child_pid = child;
/* Signal the child process to go */
kill(child, SIGUSR2);
ASSERT_EQ(0, sem_post(sem)) << strerror(errno);
int child_status;
wait(&child_status);