linux-kernel - [PATCH 17/20] signal/x86: In emulate_vsyscall force a signal instead of calling do

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Date:   Wed, 20 Oct 2021 12:44:03 -0500
From:   "Eric W. Biederman" <ebiederm@...ssion.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-arch@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Al Viro <viro@...IV.linux.org.uk>,
        Kees Cook <keescook@...omium.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Andy Lutomirski <luto@...nel.org>
Subject: [PATCH 17/20] signal/x86: In emulate_vsyscall force a signal instead of calling do_exit

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@...nel.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
---
 arch/x86/entry/vsyscall/vsyscall_64.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/entry/vsyscall/vsyscall_64.c b/arch/x86/entry/vsyscall/vsyscall_64.c
index 1b40b9297083..0b6b277ee050 100644
--- 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 error_code,
 	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)
-- 
2.20.1