Date: Tue, 19 Sep 2023 15:39:21 +0300 From: Dmitry Chagin <dchagin@freebsd.org> To: Konstantin Belousov <kostikbel@gmail.com> Cc: src-committers@freebsd.org, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org Subject: Re: git: 227d01c1bc7c - main - linux(4): On Linux SIGKILL can not be reset to default Message-ID: <ZQmWeRFgwZuQER3U@heemeyer.club> In-Reply-To: <ZQl7EqzSyrLt7a7V@kib.kiev.ua> References: <202309181453.38IErP3M046039@gitrepo.freebsd.org> <ZQi7phO8tYoAcvpu@kib.kiev.ua> <ZQlyUz9wVeKY6s5D@heemeyer.club> <ZQl7EqzSyrLt7a7V@kib.kiev.ua>
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On Tue, Sep 19, 2023 at 01:42:26PM +0300, Konstantin Belousov wrote: > On Tue, Sep 19, 2023 at 01:05:07PM +0300, Dmitry Chagin wrote: > > On Tue, Sep 19, 2023 at 12:05:42AM +0300, Konstantin Belousov wrote: > > > On Mon, Sep 18, 2023 at 02:53:25PM +0000, Dmitry Chagin wrote: > > > > The branch main has been updated by dchagin: > > > > > > > > URL: https://cgit.FreeBSD.org/src/commit/?id=227d01c1bc7caf2e838ee6eef1e6a3cc81d79d1b > > > > > > > > commit 227d01c1bc7caf2e838ee6eef1e6a3cc81d79d1b > > > > Author: Dmitry Chagin <dchagin@FreeBSD.org> > > > > AuthorDate: 2023-09-18 14:53:01 +0000 > > > > Commit: Dmitry Chagin <dchagin@FreeBSD.org> > > > > CommitDate: 2023-09-18 14:53:01 +0000 > > > > > > > > linux(4): On Linux SIGKILL can not be reset to default > > > > > > > > MFC after: 1 week > > > > --- > > > > sys/compat/linux/linux_signal.c | 5 ++++- > > > > 1 file changed, 4 insertions(+), 1 deletion(-) > > > > > > > > diff --git a/sys/compat/linux/linux_signal.c b/sys/compat/linux/linux_signal.c > > > > index e3e3fc74a6a9..9a84700b3949 100644 > > > > --- a/sys/compat/linux/linux_signal.c > > > > +++ b/sys/compat/linux/linux_signal.c > > > > @@ -170,6 +170,7 @@ linux_do_sigaction(struct thread *td, int linux_sig, l_sigaction_t *linux_nsa, > > > > > > > > if (!LINUX_SIG_VALID(linux_sig)) > > > > return (EINVAL); > > > > + sig = linux_to_bsd_signal(linux_sig); > > > > > > > > osa = (linux_osa != NULL) ? &oact : NULL; > > > > if (linux_nsa != NULL) { > > > > @@ -180,9 +181,11 @@ linux_do_sigaction(struct thread *td, int linux_sig, l_sigaction_t *linux_nsa, > > > > linux_ktrsigset(&linux_nsa->lsa_mask, > > > > sizeof(linux_nsa->lsa_mask)); > > > > #endif > > > > + if ((sig == SIGKILL || sig == SIGSTOP) && > > > > + nsa->sa_handler == SIG_DFL) > > > > + return (EINVAL); > > > This is excessive: look at kern_sigaction() around line 822. > > > > > > > Well, I checkd that before, Bruce added this check a long time ago, > > however, Bruce's change allows the handler to be set to SIG_DFL. > > And I haven't found an explicit statement of how it should be in POSIX, > > so I think it's Linux specific > > > > If kern_sigaction() allows to change SIGKILL or SIGSTOP disposition from > default, we have a serious issue. The check above simply repeats the > check from kern_sigaction(). Hmm, why? Native kern_sigaction check: if ((sig == SIGKILL || sig == SIGSTOP) && act->sa_handler != SIG_DFL) { ^^^^^^^ this allows to set sa_handler to SIG_DFL, but Linux forbids this mtx_unlock(&ps->ps_mtx); PROC_UNLOCK(p); return (EINVAL); } And I found in the POSIX: It is unspecified whether an attempt to set the action for a signal that cannot be caught or ignored to SIG_DFL is ignored or causes an error to be returned with errno set to [EINVAL]. The sigaction() function may fail if: [EINVAL] An attempt was made to set the action to SIG_DFL for a signal that cannot be caught or ignored (or both). Linux returns EINVAL in that case, FreeBSD does not, both are valid?
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