[PATCH 4/8] fork: Add USER_WORKER flag to ignore signals

From: Mike Christie
Date: Wed Feb 02 2022 - 16:03:02 EST


From: Christian Brauner <christian.brauner@xxxxxxxxxx>

Since:

commit 10ab825bdef8 ("change kernel threads to ignore signals instead of
blocking them")

kthreads have been ignoring signals by default, and the vhost layer has
never had a need to change that. This patch adds an option flag,
USER_WORKER_SIG_IGN, handled in copy_process() after copy_sighand()
and copy_signals() so vhost_tasks added in the next patches can continue
to ignore singals.

Signed-off-by: Christian Brauner <christian.brauner@xxxxxxxxxx>
Signed-off-by: Mike Christie <michael.christie@xxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
---
include/linux/sched/task.h | 1 +
kernel/fork.c | 3 +++
2 files changed, 4 insertions(+)

diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
index 706ca3dc3423..c001d0fa1426 100644
--- a/include/linux/sched/task.h
+++ b/include/linux/sched/task.h
@@ -21,6 +21,7 @@ struct css_set;
#define USER_WORKER BIT(0)
#define USER_WORKER_IO BIT(1)
#define USER_WORKER_NO_FILES BIT(2)
+#define USER_WORKER_SIG_IGN BIT(3)

struct kernel_clone_args {
u64 flags;
diff --git a/kernel/fork.c b/kernel/fork.c
index 81a1096d6ee9..6a04860fa1ae 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2185,6 +2185,9 @@ static __latent_entropy struct task_struct *copy_process(
if (retval)
goto bad_fork_cleanup_io;

+ if (args->worker_flags & USER_WORKER_SIG_IGN)
+ ignore_signals(p);
+
stackleak_task_init(p);

if (pid != &init_struct_pid) {
--
2.25.1