commit d21918e5a94a862ccb297b9f2be38574c865fda0
author Eric W. Biederman <ebiederm@xmission.com> Wed Jun 23 16:51:49 2021 -0500
committer Eric W. Biederman <ebiederm@xmission.com> Thu Aug 26 18:06:41 2021 -0500
tree 19443747e3d286338f0f19bcacff983597c8b727
parent 307d522f5eb86cd6ac8c905f5b0577dedac54ec5

signal/seccomp: Dump core when there is only one live thread

Replace get_nr_threads with atomic_read(&current->signal->live) as
that is a more accurate number that is decremented sooner.

Acked-by: Kees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/87lf6z6qbd.fsf_-_@disp2133
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

kernel/seccomp.c

diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index abcbd3d..afa4db0 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -1264,7 +1264,7 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
 		seccomp_log(this_syscall, SIGSYS, action, true);
 		/* Dump core only if this is the last remaining thread. */
 		if (action != SECCOMP_RET_KILL_THREAD ||
-		    get_nr_threads(current) == 1) {
+		    (atomic_read(&current->signal->live) == 1)) {
 			/* Show the original registers in the dump. */
 			syscall_rollback(current, current_pt_regs());
 			/* Trigger a coredump with SIGSYS */