signal/s390: Use force_sigsegv in default_trap_handler

commit 9bc508cf0791c8e5a37696de1a046d746fcbd9d8 upstream.

Reading the history it is unclear why default_trap_handler calls
do_exit.  It is not even menthioned in the commit where the change
happened.  My best guess is that because it is unknown why the
exception happened it was desired to guarantee the process never
returned to userspace.

Using do_exit(SIGSEGV) has the problem that it will only terminate one
thread of a process, leaving the process in an undefined state.

Use force_sigsegv(SIGSEGV) instead which effectively has the same
behavior except that is uses the ordinary signal mechanism and
terminates all threads of a process and is generally well defined.

Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: linux-s390@vger.kernel.org
Fixes: ca2ab03237ec ("[PATCH] s390: core changes")
History Tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Link: https://lkml.kernel.org/r/20211020174406.17889-11-ebiederm@xmission.com
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: Thomas Backlund <tmb@iki.fi>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/s390/kernel/traps.c b/arch/s390/kernel/traps.c
index bcefc2173de45b081c5287251f390ed746ae49ef..51729ea2cf8e75d1b0ccf95f0445692c05f186c4 100644 (file)
--- a/arch/s390/kernel/traps.c
+++ b/arch/s390/kernel/traps.c
@@ -84,7 +84,7 @@ static void default_trap_handler(struct pt_regs *regs)
 {
        if (user_mode(regs)) {
                report_user_fault(regs, SIGSEGV, 0);
-               do_exit(SIGSEGV);
+               force_sigsegv(SIGSEGV);
        } else
                die(regs, "Unknown program exception");
 }