K 10
svn:author
V 6
kevans
K 8
svn:date
V 27
2020-04-13T17:55:31.320219Z
K 7
svn:log
V 508
close_range/closefrom: fix regression from close_range introduction

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

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