fork: kill the pointless lower_32_bits() in create_io_thread(), kernel_thread(), and user_mode_thread()

Browse source

Unlike sys_clone(), these helpers have only in kernel users which should
pass the correct "flags" argument.  lower_32_bits(flags) just adds the
unnecessary confusion and doesn't allow to use the CLONE_ flags which
don't fit into 32 bits.

create_io_thread() looks especially confusing because:

	- "flags" is a compile-time constant, so lower_32_bits() simply
	  has no effect

	- .exit_signal = (lower_32_bits(flags) & CSIGNAL) is harmless but
	  doesn't look right, copy_process(CLONE_THREAD) will ignore this
	  argument anyway.

None of these helpers actually need CLONE_UNTRACED or "& ~CSIGNAL", but
their presence does not add any confusion and improves code clarity.

Link: https://lkml.kernel.org/r/20250820163946.GA18549@redhat.com
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Kees Cook <kees@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

...

This commit is contained in:

Oleg Nesterov 2025-08-20 18:39:46 +02:00 • committed by Andrew Morton

parent b32730e68d

commit f7071db2fe

1 changed files with 6 additions and 10 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

16

kernel/fork.c

View file