From: ebiederm@xmission.com (Eric W. Biederman)
To: Christoph Hellwig <hch@lst.de>
Cc: linux-arch@vger.kernel.org, Nick Hu <nickhu@andestech.com>,
linux-kernel@vger.kernel.org, Palmer Dabbelt <palmer@dabbelt.com>,
Greentime Hu <green.hu@gmail.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
Andrew Morton <akpm@linux-foundation.org>,
Vincent Chen <deanbo422@gmail.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-riscv@lists.infradead.org
Subject: Re: [PATCH 6/6] exec: use force_uaccess_begin during exec and exit
Date: Tue, 14 Jul 2020 22:33:05 -0500 [thread overview]
Message-ID: <87v9ip4fm6.fsf@x220.int.ebiederm.org> (raw)
In-Reply-To: <20200714105505.935079-7-hch@lst.de> (Christoph Hellwig's message of "Tue, 14 Jul 2020 12:55:05 +0200")
Christoph Hellwig <hch@lst.de> writes:
> Both exec and exit want to ensure that the uaccess routines actually do
> access user pointers. Use the newly added force_uaccess_begin helper
> instead of an open coded set_fs for that to prepare for kernel builds
> where set_fs() does not exist.
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Have you played with a tree with all of your patches
and placing force_uaccess_begin in init/main.c:start_kernel?
Somewhere deep in the arch code we seem to have it all backwards
and kernel threads are all set_fs(KERNEL_DS). So just putting
a force_uaccess_begin somewhere very early should be enough
to switch things around.
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> fs/exec.c | 7 ++++++-
> kernel/exit.c | 2 +-
> 2 files changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/fs/exec.c b/fs/exec.c
> index e6e8a9a7032784..769af470b69124 100644
> --- a/fs/exec.c
> +++ b/fs/exec.c
> @@ -1380,7 +1380,12 @@ int begin_new_exec(struct linux_binprm * bprm)
> if (retval)
> goto out_unlock;
>
> - set_fs(USER_DS);
> + /*
> + * Ensure that the uaccess routines can actually operate on userspace
> + * pointers:
> + */
> + force_uaccess_begin();
> +
> me->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD |
> PF_NOFREEZE | PF_NO_SETAFFINITY);
> flush_thread();
> diff --git a/kernel/exit.c b/kernel/exit.c
> index 727150f2810338..17d486a20f0dc6 100644
> --- a/kernel/exit.c
> +++ b/kernel/exit.c
> @@ -731,7 +731,7 @@ void __noreturn do_exit(long code)
> * mm_release()->clear_child_tid() from writing to a user-controlled
> * kernel address.
> */
> - set_fs(USER_DS);
> + force_uaccess_begin();
>
> if (unlikely(in_atomic())) {
> pr_info("note: %s[%d] exited with preempt_count %d\n",
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next prev parent reply other threads:[~2020-07-15 3:36 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-14 10:54 clean up address limit helpers v2 Christoph Hellwig
2020-07-14 10:55 ` [PATCH 1/6] syscalls: use uaccess_kernel in addr_limit_user_check Christoph Hellwig
2020-07-18 1:38 ` Guenter Roeck
2020-07-18 9:48 ` Christoph Hellwig
2020-07-18 14:54 ` Guenter Roeck
2020-07-20 22:10 ` Guenter Roeck
2020-07-21 4:58 ` Christoph Hellwig
2020-07-21 5:15 ` Guenter Roeck
2020-07-21 5:20 ` Christoph Hellwig
2020-07-21 5:30 ` Guenter Roeck
2020-07-21 5:35 ` Christoph Hellwig
2020-07-14 10:55 ` [PATCH 2/6] nds32: use uaccess_kernel in show_regs Christoph Hellwig
2020-07-14 10:55 ` [PATCH 3/6] riscv: include <asm/pgtable.h> in <asm/uaccess.h> Christoph Hellwig
2020-07-14 10:55 ` [PATCH 4/6] uaccess: remove segment_eq Christoph Hellwig
2020-07-14 15:27 ` Linus Torvalds
2020-07-14 10:55 ` [PATCH 5/6] uaccess: add force_uaccess_{begin,end} helpers Christoph Hellwig
2020-07-14 15:29 ` Linus Torvalds
2020-07-14 10:55 ` [PATCH 6/6] exec: use force_uaccess_begin during exec and exit Christoph Hellwig
2020-07-15 3:33 ` Eric W. Biederman [this message]
2020-07-15 6:06 ` Christoph Hellwig
2020-07-16 23:49 ` clean up address limit helpers v2 Andrew Morton
2020-07-17 6:06 ` Christoph Hellwig
2020-07-20 15:54 ` [PATCH 0/6] arm: don't call addr_limit_user_check for nommu Christoph Hellwig
-- strict thread matches above, loose matches on Subject: below --
2020-07-10 13:57 clean up address limit helpers Christoph Hellwig
2020-07-10 13:57 ` [PATCH 6/6] exec: use force_uaccess_begin during exec and exit Christoph Hellwig
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