[klibc] Debian #988027: sigsetjmp ignores second argument, siglongjmp always restores signals

[Thorsten Glaser]

As indicated below, I can provide a fix for this (but it should be
easy enough); also for the s390x setjmp/longjmp bug #943425 once the
porters clarify the ABI (i.e. which registers to save), if needed.

---------- Forwarded message ----------
Message-ID: <162007527823.6523.7891920735984618909.reportbug at zelenka.debian.org>
Subject: Bug#988027: klibc: sigsetjmp ignores second argument,
    siglongjmp always restores signals

Package: libklibc-dev
Version: 2.0.8-6
Severity: serious
Justification: spec violation, affecting release architectures
X-Debbugs-Cc: tg at debian.org

Found during debugging of #943425:

- usr/include/setjmp.h

	struct __sigjmp_buf {
		jmp_buf __jmpbuf;
		sigset_t __sigs;
	};
  => does not contain information whether __sigs was saved

	#define sigsetjmp(__env, __save) \
	({ \
	  struct __sigjmp_buf *__e = (__env); \
	  sigprocmask(0, NULL, &__e->__sigs); \
	  setjmp(__e->__jmpbuf); \
	})
  => ignores the __save argument

- usr/klibc/siglongjmp.c

	__noreturn siglongjmp(sigjmp_buf buf, int retval)
	{
		sigprocmask(SIG_SETMASK, &buf->__sigs, NULL);
		longjmp(buf->__jmpbuf, retval);
  => always restores __sigs

This is in direct violation to the Debian sigsetjmp(3) docs...

       If, and only if, the savesigs argument provided to sigsetjmp() is  non-
       zero, the process's current signal mask is saved in env and will be re-
       stored if a siglongjmp() is later performed with this env.

... and POSIX:

     * The siglongjmp() function shall restore the saved signal mask if and
       only if the env argument was initialized by a call to [9]sigsetjmp()
       with a non-zero savemask argument.
  Q: https://pubs.opengroup.org/onlinepubs/9699919799/functions/siglongjmp.html


If necessary I can provide a patch to fix this.

-- System Information:
Debian Release: 11.0
  APT prefers unstable-debug
  APT policy: (500, 'unstable-debug'), (500, 'unstable')
Architecture: s390x

Kernel: Linux 4.19.0-16-s390x (SMP w/2 CPU threads)
Locale: LANG=C, LC_CTYPE=C.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /bin/dash
Init: unable to detect

Versions of packages libklibc-dev depends on:
ii  libklibc        2.0.8-6
ii  linux-libc-dev  5.10.28-1

libklibc-dev recommends no packages.

libklibc-dev suggests no packages.

-- no debconf information