[PATCH 5.15 263/279] signal/x86: In emulate_vsyscall force a signal instead of calling do_exit

[Greg Kroah-Hartman]

From: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>

commit 695dd0d634df8903e5ead8aa08d326f63b23368a upstream.

Directly calling do_exit with a signal number has the problem that
all of the side effects of the signal don't happen, such as
killing all of the threads of a process instead of just the
calling thread.

So replace do_exit(SIGSYS) with force_fatal_sig(SIGSYS) which
causes the signal handling to take it's normal path and work
as expected.

Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Link: https://lkml.kernel.org/r/20211020174406.17889-17-ebiederm@xxxxxxxxxxxx
Signed-off-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
Cc: Thomas Backlund <tmb@xxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 arch/x86/entry/vsyscall/vsyscall_64.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/arch/x86/entry/vsyscall/vsyscall_64.c
+++ b/arch/x86/entry/vsyscall/vsyscall_64.c
@@ -226,7 +226,8 @@ bool emulate_vsyscall(unsigned long erro
 	if ((!tmp && regs->orig_ax != syscall_nr) || regs->ip != address) {
 		warn_bad_vsyscall(KERN_DEBUG, regs,
 				  "seccomp tried to change syscall nr or ip");
-		do_exit(SIGSYS);
+		force_fatal_sig(SIGSYS);
+		return true;
 	}
 	regs->orig_ax = -1;
 	if (tmp)