Linus Torvalds 1ec6574a3c This set of changes updates init and user mode helper tasks to be ... ordinary user mode tasks. In commit 40966e316f ("kthread: Ensure struct kthread is present for all kthreads") caused init and the user mode helper threads that call kernel_execve to have struct kthread allocated for them. This struct kthread going away during execve in turned made a use after free of struct kthread possible. The commit 343f4c49f2 ("kthread: Don't allocate kthread_struct for init and umh") is enough to fix the use after free and is simple enough to be backportable. The rest of the changes pass struct kernel_clone_args to clean things up and cause the code to make sense. In making init and the user mode helpers tasks purely user mode tasks I ran into two complications. The function task_tick_numa was detecting tasks without an mm by testing for the presence of PF_KTHREAD. The initramfs code in populate_initrd_image was using flush_delayed_fput to ensuere the closing of all it's file descriptors was complete, and flush_delayed_fput does not work in a userspace thread. I have looked and looked and more complications and in my code review I have not found any, and neither has anyone else with the code sitting in linux-next. Link: https://lkml.kernel.org/r/87mtfu4up3.fsf@email.froward.int.ebiederm.org Eric W. Biederman (8): kthread: Don't allocate kthread_struct for init and umh fork: Pass struct kernel_clone_args into copy_thread fork: Explicity test for idle tasks in copy_thread fork: Generalize PF_IO_WORKER handling init: Deal with the init process being a user mode process fork: Explicitly set PF_KTHREAD fork: Stop allowing kthreads to call execve sched: Update task_tick_numa to ignore tasks without an mm arch/alpha/kernel/process.c | 13 ++++++------ arch/arc/kernel/process.c | 13 ++++++------ arch/arm/kernel/process.c | 12 ++++++----- arch/arm64/kernel/process.c | 12 ++++++----- arch/csky/kernel/process.c | 15 ++++++------- arch/h8300/kernel/process.c | 10 ++++----- arch/hexagon/kernel/process.c | 12 ++++++----- arch/ia64/kernel/process.c | 15 +++++++------ arch/m68k/kernel/process.c | 12 ++++++----- arch/microblaze/kernel/process.c | 12 ++++++----- arch/mips/kernel/process.c | 13 ++++++------ arch/nios2/kernel/process.c | 12 ++++++----- arch/openrisc/kernel/process.c | 12 ++++++----- arch/parisc/kernel/process.c | 18 +++++++++------- arch/powerpc/kernel/process.c | 15 +++++++------ arch/riscv/kernel/process.c | 12 ++++++----- arch/s390/kernel/process.c | 12 ++++++----- arch/sh/kernel/process_32.c | 12 ++++++----- arch/sparc/kernel/process_32.c | 12 ++++++----- arch/sparc/kernel/process_64.c | 12 ++++++----- arch/um/kernel/process.c | 15 +++++++------ arch/x86/include/asm/fpu/sched.h | 2 +- arch/x86/include/asm/switch_to.h | 8 +++---- arch/x86/kernel/fpu/core.c | 4 ++-- arch/x86/kernel/process.c | 18 +++++++++------- arch/xtensa/kernel/process.c | 17 ++++++++------- fs/exec.c | 8 ++++--- include/linux/sched/task.h | 8 +++++-- init/initramfs.c | 2 ++ init/main.c | 2 +- kernel/fork.c | 46 +++++++++++++++++++++++++++++++++------- kernel/sched/fair.c | 2 +- kernel/umh.c | 6 +++--- 33 files changed, 234 insertions(+), 160 deletions(-) Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> -----BEGIN PGP SIGNATURE----- iQIzBAABCgAdFiEEgjlraLDcwBA2B+6cC/v6Eiajj0AFAmKaR/MACgkQC/v6Eiaj j0Aayg/7Bx66872d9c6igkJ+MPCTuh+v9QKCGwiYEmiU4Q5sVAFB0HPJO27qC14u 630X0RFNZTkPzNNEJNIW4kw6Dj8s8YRKf+FgQAVt4SzdRwT7eIPDjk1nGraopPJ3 O04pjvuTmUyidyViRyFcf2ptx/pnkrwP8jUSc+bGTgfASAKAgAokqKE5ecjewbBc Y/EAkQ6QW7KxPjeSmpAHwI+t3BpBev9WEC4PbhRhsBCQFO2+PJiklvqdhVNBnIjv qUezll/1xv9UYgniB15Q4Nb722SmnWSU3r8as1eFPugzTHizKhufrrpyP+KMK1A0 tdtEJNs5t2DZF7ZbGTFSPqJWmyTYLrghZdO+lOmnaSjHxK4Nda1d4NzbefJ0u+FE tutewowvHtBX6AFIbx+H3O+DOJM2IgNMf+ReQDU/TyNyVf3wBrTbsr9cLxypIJIp zze8npoLMlB7B4yxVo5ES5e63EXfi3iHl0L3/1EhoGwriRz1kWgVLUX/VZOUpscL RkJHsW6bT8sqxPWAA5kyWjEN+wNR2PxbXi8OE4arT0uJrEBMUgDCzydzOv5tJB00 mSQdytxH9LVdsmxBKAOBp5X6WOLGA4yb1cZ6E/mEhlqXMpBDF1DaMfwbWqxSYi4q sp5zU3SBAW0qceiZSsWZXInfbjrcQXNV/DkDRDO9OmzEZP4m1j0= =x6fy -----END PGP SIGNATURE----- Merge tag 'kthread-cleanups-for-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace Pull kthread updates from Eric Biederman: "This updates init and user mode helper tasks to be ordinary user mode tasks. Commit 40966e316f ("kthread: Ensure struct kthread is present for all kthreads") caused init and the user mode helper threads that call kernel_execve to have struct kthread allocated for them. This struct kthread going away during execve in turned made a use after free of struct kthread possible. Here, commit 343f4c49f2 ("kthread: Don't allocate kthread_struct for init and umh") is enough to fix the use after free and is simple enough to be backportable. The rest of the changes pass struct kernel_clone_args to clean things up and cause the code to make sense. In making init and the user mode helpers tasks purely user mode tasks I ran into two complications. The function task_tick_numa was detecting tasks without an mm by testing for the presence of PF_KTHREAD. The initramfs code in populate_initrd_image was using flush_delayed_fput to ensuere the closing of all it's file descriptors was complete, and flush_delayed_fput does not work in a userspace thread. I have looked and looked and more complications and in my code review I have not found any, and neither has anyone else with the code sitting in linux-next" * tag 'kthread-cleanups-for-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: sched: Update task_tick_numa to ignore tasks without an mm fork: Stop allowing kthreads to call execve fork: Explicitly set PF_KTHREAD init: Deal with the init process being a user mode process fork: Generalize PF_IO_WORKER handling fork: Explicity test for idle tasks in copy_thread fork: Pass struct kernel_clone_args into copy_thread kthread: Don't allocate kthread_struct for init and umh		2022-06-03 16:03:05 -07:00
..
api.h	x86/prctl: Remove pointless task argument	2022-05-13 12:56:28 +02:00
regset.h	x86: switch to ->regset_get()	2020-07-27 14:31:07 -04:00
sched.h	fork: Generalize PF_IO_WORKER handling	2022-05-07 09:01:59 -05:00
signal.h	x86/fpu: Remove duplicate copy_fpstate_to_sigframe() prototype	2021-12-10 19:13:06 +01:00
types.h	x86/fpu: Add uabi_size to guest_fpu	2022-01-14 13:44:40 -05:00
xcr.h	x86/fpu: Optimize out sigframe xfeatures when in init state	2021-11-03 22:42:35 +01:00
xstate.h	x86/fpu: Optimize out sigframe xfeatures when in init state	2021-11-03 22:42:35 +01:00