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close_range/closefrom: fix regression from close_range introduction

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close_range will clamp the range between [0, fdp->fd_lastfile], but failed
to take into account that fdp->fd_lastfile can become -1 if all fds are
closed. =-( In this scenario, just return because there's nothing further we
can do at the moment.

Add a test case for this, fork() and simply closefrom(0) twice in the child;
on the second invocation, fdp->fd_lastfile == -1 and will trigger a panic
before this change.

X-MFC-With:	r359836
This commit is contained in:
Kyle Evans 2020-04-13 17:55:31 +00:00
parent 7c5e60c72e
commit 605c4cda2f
2 changed files with 25 additions and 1 deletions
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8
sys/kern/kern_descrip.c
View File

@ -1333,6 +1333,14 @@ kern_close_range(struct thread *td, u_int lowfd, u_int highfd)
ret = EINVAL;
goto out;
}
/*
* If fdp->fd_lastfile == -1, we're dealing with either a fresh file
* table or one in which every fd has been closed. Just return
* successful; there's nothing left to do.
*/
if (fdp->fd_lastfile == -1)
goto out;
/* Clamped to [lowfd, fd_lastfile] */
highfd = MIN(highfd, fdp->fd_lastfile);
for (fd = lowfd; fd <= highfd; fd++) {

18
tests/sys/file/closefrom_test.c
View File

@ -146,7 +146,7 @@ main(void)
pid_t pid;
int fd, i, start;
printf("1..19\n");
printf("1..20\n");
/* We better start up with fd's 0, 1, and 2 open. */
start = devnull();
@ -309,5 +309,21 @@ main(void)
fail("close_range", "highest fd %d", fd);
ok("close_range");
/* Fork a child process to test closefrom(0) twice. */
pid = fork();
if (pid < 0)
fail_err("fork");
if (pid == 0) {
/* Child. */
closefrom(0);
closefrom(0);
cok(info, "closefrom(0)");
}
if (wait(NULL) < 0)
fail_err("wait");
if (info->failed)
fail(info->tag, "%s", info->message);
ok(info->tag);
return (0);
}