Date: Sun, 6 Mar 2022 01:20:37 +0100 From: Peter <pmc@citylink.dinoex.sub.org> To: Eugene Grosbein <eugen@grosbein.net> Cc: freebsd-stable@freebsd.org, Konstantin Belousov <kib@freebsd.org> Subject: Re: Program crashes on stable/13 (but not on 12.3) Message-ID: <YiP%2BVWC6VSuDDeji@gate.intra.daemon.contact> In-Reply-To: <bf0ed399-f0e6-c98e-4d6f-d2da10af261f@grosbein.net> References: <YiO5cO967R/D2cIm@gate.intra.daemon.contact> <bf0ed399-f0e6-c98e-4d6f-d2da10af261f@grosbein.net>
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On Sun, Mar 06, 2022 at 04:26:10AM +0700, Eugene Grosbein wrote:
! 06.03.2022 2:26, Peter wrote:
!
! Adding kib@ to CC: in case this is connected to recent commit by him.
It is.
! > Hija,
! >
! > this program crashes SEGV on stable/13 after 135962 iterations,
! > but continues to run on 12.3.
! >
! > My stable/13 is still at 22ba2970766 - if You happen to be on a
! > newer level, then please just try this out.
! >
! > ------------------------------------------------------
! > #include <unistd.h>
! > #include <fcntl.h>
! > #include <stdio.h>
! >
! > main() {
! > char buf[] = "12345678901234567890123456789012345678901234567890";
! > int fd = open("/dev/null", O_RDONLY);
! > int i = 0;
! >
! > close(1);
! > dup2(fd, 1);
! > close(fd);
! >
! > while(1) {
! > fputs(buf, stdout);
! > fflush(stdout);
! > i++;
! > fprintf(stderr, "%d\n", i);
! > }
! > }
! > ------------------------------------------------------
! >
! > I know that the code is bogus, but this is exactly what one of our
! > ports does (and why it started to crash after upgrading to stable/13).
! >
! > And I think it should not SEGV, anyway.
! >
! > For the full story, read here:
! >
! > https://forums.freebsd.org/threads/random-program-crashes-no-coredumps-and-error-94.84285/
!
! fflush() in our libc recently got some change due to very old PR
! https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=76398
!
! That change was merged to stable/13 after 13.0-RELEASE:
! https://cgit.freebsd.org/src/commit/?id=afa9a1f5ec9974793a8744c55036ef5c4d08903d
Yes, this is the cause, I now checked before and after. I don't really
see why it does what it does, even less why it only happens after so
many invocations.
I wouldn't bother much about it, because such crappy code somehow
deserves to crash - but then, concerned is sysutils/bareos-client
backup tool, and arbitrary memory corruption appears there, and I
am not sure if this could lead to silently corrupted backup data.
So it's probably not the best idea to keep this into 13.1.
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