From: "Eric W. Biederman" <ebiederm@xmission.com>
To: Arnd Bergmann <arnd@kernel.org>
Cc: mark.rutland@arm.com, dalias@libc.org,
linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org,
peterz@infradead.org, linux-mips@vger.kernel.org,
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linux-riscv@lists.infradead.org, will@kernel.org,
Christoph Hellwig <hch@lst.de>,
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Linus Torvalds <torvalds@linux-foundation.org>,
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Subject: Re: [PATCH v2 18/18] uaccess: drop maining CONFIG_SET_FS users
Date: Thu, 17 Feb 2022 16:36:20 -0600 [thread overview]
Message-ID: <8735khi0ij.fsf@email.froward.int.ebiederm.org> (raw)
In-Reply-To: <20220216131332.1489939-19-arnd@kernel.org> (Arnd Bergmann's message of "Wed, 16 Feb 2022 14:13:32 +0100")
Arnd Bergmann <arnd@kernel.org> writes:
> From: Arnd Bergmann <arnd@arndb.de>
>
> There are no remaining callers of set_fs(), so CONFIG_SET_FS
> can be removed globally, along with the thread_info field and
> any references to it.
>
> This turns access_ok() into a cheaper check against TASK_SIZE_MAX.
>
> With CONFIG_SET_FS gone, so drop all remaining references to
> set_fs()/get_fs(), mm_segment_t and uaccess_kernel().
For the bits I have looked at recently, and think I understand.
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> fs/exec.c | 6 --
> kernel/exit.c | 14 -----
> kernel/kthread.c | 5 --
>
> diff --git a/fs/exec.c b/fs/exec.c
> index 79f2c9483302..bc68a0c089ac 100644
> --- a/fs/exec.c
> +++ b/fs/exec.c
> @@ -1303,12 +1303,6 @@ int begin_new_exec(struct linux_binprm * bprm)
> if (retval)
> goto out_unlock;
>
> - /*
> - * Ensure that the uaccess routines can actually operate on userspace
> - * pointers:
> - */
> - force_uaccess_begin();
> -
> if (me->flags & PF_KTHREAD)
> free_kthread_struct(me);
> me->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD |
> diff --git a/kernel/exit.c b/kernel/exit.c
> index b00a25bb4ab9..0884a75bc2f8 100644
> --- a/kernel/exit.c
> +++ b/kernel/exit.c
> @@ -737,20 +737,6 @@ void __noreturn do_exit(long code)
>
> WARN_ON(blk_needs_flush_plug(tsk));
>
> - /*
> - * If do_dead is called because this processes oopsed, it's possible
> - * that get_fs() was left as KERNEL_DS, so reset it to USER_DS before
> - * continuing. Amongst other possible reasons, this is to prevent
> - * mm_release()->clear_child_tid() from writing to a user-controlled
> - * kernel address.
> - *
> - * On uptodate architectures force_uaccess_begin is a noop. On
> - * architectures that still have set_fs/get_fs in addition to handling
> - * oopses handles kernel threads that run as set_fs(KERNEL_DS) by
> - * default.
> - */
> - force_uaccess_begin();
> -
> kcov_task_exit(tsk);
>
> coredump_task_exit(tsk);
> diff --git a/kernel/kthread.c b/kernel/kthread.c
> index 38c6dd822da8..16c2275d4b50 100644
> --- a/kernel/kthread.c
> +++ b/kernel/kthread.c
> @@ -55,7 +55,6 @@ struct kthread {
> int result;
> int (*threadfn)(void *);
> void *data;
> - mm_segment_t oldfs;
> struct completion parked;
> struct completion exited;
> #ifdef CONFIG_BLK_CGROUP
> @@ -1441,8 +1440,6 @@ void kthread_use_mm(struct mm_struct *mm)
> mmdrop(active_mm);
> else
> smp_mb();
> -
> - to_kthread(tsk)->oldfs = force_uaccess_begin();
> }
> EXPORT_SYMBOL_GPL(kthread_use_mm);
>
> @@ -1457,8 +1454,6 @@ void kthread_unuse_mm(struct mm_struct *mm)
> WARN_ON_ONCE(!(tsk->flags & PF_KTHREAD));
> WARN_ON_ONCE(!tsk->mm);
>
> - force_uaccess_end(to_kthread(tsk)->oldfs);
> -
> task_lock(tsk);
> /*
> * When a kthread stops operating on an address space, the loop
next prev parent reply other threads:[~2022-02-17 22:54 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-16 13:13 [PATCH v2 00/18] clean up asm/uaccess.h, kill set_fs for good Arnd Bergmann
2022-02-16 13:13 ` [PATCH v2 01/18] uaccess: fix integer overflow on access_ok() Arnd Bergmann
2022-02-16 13:13 ` [PATCH v2 02/18] uaccess: fix nios2 and microblaze get_user_8() Arnd Bergmann
2022-02-16 13:35 ` David Laight
2022-02-18 6:25 ` Christoph Hellwig
2022-02-25 4:28 ` Dinh Nguyen
2022-02-16 13:13 ` [PATCH v2 03/18] nds32: fix access_ok() checks in get/put_user Arnd Bergmann
2022-02-18 6:25 ` Christoph Hellwig
2022-02-16 13:13 ` [PATCH v2 04/18] sparc64: add __{get,put}_kernel_nocheck() Arnd Bergmann
2022-02-16 13:13 ` [PATCH v2 05/18] x86: remove __range_not_ok() Arnd Bergmann
2022-02-18 6:28 ` Christoph Hellwig
2022-02-18 7:29 ` Arnd Bergmann
2022-02-18 15:45 ` David Laight
2022-02-16 13:13 ` [PATCH v2 06/18] x86: use more conventional access_ok() definition Arnd Bergmann
2022-02-18 6:29 ` Christoph Hellwig
2022-02-16 13:13 ` [PATCH v2 07/18] nios2: drop access_ok() check from __put_user() Arnd Bergmann
2022-02-18 6:29 ` Christoph Hellwig
2022-02-23 23:30 ` Dinh Nguyen
2022-02-24 7:05 ` Arnd Bergmann
2022-02-16 13:13 ` [PATCH v2 08/18] uaccess: add generic __{get,put}_kernel_nofault Arnd Bergmann
2022-02-18 6:30 ` Christoph Hellwig
2022-02-18 8:55 ` Geert Uytterhoeven
2022-02-16 13:13 ` [PATCH v2 09/18] mips: use simpler access_ok() Arnd Bergmann
2022-02-21 13:24 ` Thomas Bogendoerfer
2022-02-21 14:31 ` Arnd Bergmann
2022-02-21 15:21 ` Thomas Bogendoerfer
2022-02-22 16:36 ` Thomas Bogendoerfer
2022-02-23 20:05 ` Linus Torvalds
2022-02-23 7:41 ` Thomas Bogendoerfer
2022-02-23 9:26 ` Arnd Bergmann
2022-02-16 13:13 ` [PATCH v2 10/18] m68k: fix access_ok for coldfire Arnd Bergmann
2022-02-18 6:30 ` Christoph Hellwig
2022-02-18 9:00 ` Geert Uytterhoeven
2022-02-18 9:24 ` Arnd Bergmann
2022-02-16 13:13 ` [PATCH v2 11/18] arm64: simplify access_ok() Arnd Bergmann
2022-02-16 13:13 ` [PATCH v2 12/18] uaccess: fix type mismatch warnings from access_ok() Arnd Bergmann
2022-02-18 6:31 ` Christoph Hellwig
2022-02-25 4:30 ` Dinh Nguyen
2022-02-16 13:13 ` [PATCH v2 13/18] uaccess: generalize access_ok() Arnd Bergmann
2022-02-17 7:52 ` Arnd Bergmann
2022-02-17 19:15 ` Andy Lutomirski
2022-02-18 7:16 ` Arnd Bergmann
2022-02-18 9:30 ` David Laight
2022-02-18 18:07 ` Andy Lutomirski
2022-02-18 6:34 ` Christoph Hellwig
2022-02-18 7:23 ` Arnd Bergmann
2022-02-18 9:04 ` Geert Uytterhoeven
2022-02-24 8:29 ` Stafford Horne
2022-02-24 8:41 ` Arnd Bergmann
2022-02-25 4:31 ` Dinh Nguyen
2022-02-16 13:13 ` [PATCH v2 14/18] lib/test_lockup: fix kernel pointer check for separate address spaces Arnd Bergmann
2022-02-18 6:35 ` Christoph Hellwig
2022-02-18 7:15 ` Arnd Bergmann
2022-02-16 13:13 ` [PATCH v2 15/18] sparc64: remove CONFIG_SET_FS support Arnd Bergmann
2022-02-16 18:34 ` Sam Ravnborg
2022-02-16 18:41 ` Sam Ravnborg
2022-02-16 22:01 ` Arnd Bergmann
2022-02-16 13:13 ` [PATCH v2 16/18] sh: " Arnd Bergmann
2022-02-18 6:36 ` Christoph Hellwig
2022-02-16 13:13 ` [PATCH v2 17/18] ia64: " Arnd Bergmann
2022-02-16 13:13 ` [PATCH v2 18/18] uaccess: drop maining CONFIG_SET_FS users Arnd Bergmann
2022-02-16 18:44 ` Sam Ravnborg
2022-02-16 22:02 ` Arnd Bergmann
2022-02-17 22:36 ` Eric W. Biederman [this message]
2022-02-18 6:37 ` Christoph Hellwig
2022-02-18 7:10 ` Arnd Bergmann
2022-02-18 10:18 ` Sergey Matyukevich
2022-02-24 8:45 ` Stafford Horne
2022-02-25 4:33 ` Dinh Nguyen
2022-02-17 7:20 ` [PATCH v2 00/18] clean up asm/uaccess.h, kill set_fs for good Christophe Leroy
2022-02-17 7:49 ` Arnd Bergmann
2022-02-18 2:21 ` Al Viro
2022-02-18 9:20 ` Arnd Bergmann
2022-02-18 1:50 ` Al Viro
2022-02-18 10:01 ` Christophe Leroy
2022-02-17 8:13 ` Arnd Bergmann
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