Date: Tue, 24 May 2005 12:59:07 -0400 From: Ed Maste <emaste@phaedrus.sandvine.ca> To: freebsd-stable@freebsd.org Subject: libc_r kqueue fd leak Message-ID: <20050524165907.GA20674@sandvine.com>
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We discovered a kqueue leak when running one of our 4.x applications on
FreeBSD 5.3 using the compat libc_r. It turns out it's caused by libc_r's
close() failing.
The libc_r close (in uthread_close.c) calls fstat() on the file
descriptor. On 4.x this succeeds, while on 5.x the fstat() on the kqueue()
fd returns -1 with errno=0. The close() in libc_r then returns this error
without doing the actual close syscall.
I built the test application shown below on a 4.7 and 5.3 machine
and fstat returns 0 on 4.7, -1 on 5.3. If the test app is linked against
libc_r then the close() fails too.
fstat(2) indicates that fstat() returns a mostly-zeroed buffer for a socket
fd, but gives no indication of what should happen for a kqueue fd. What is
the expected behaviour here? The issue could be fixed by either having the
kernel not fail the fstat, or making libc_r ignore the failure and continue
on with the close.
== kqueue.c ==
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/event.h>
#include <errno.h>
int main()
{
struct stat sb;
int kq=kqueue();
printf("fstat returns %d (%d)\n", fstat(kq, &sb), errno);
printf("close returns %d (%d)\n", close(kq), errno);
}
--
Ed Maste, Sandvine Incorporated
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