From: Alan Cox <alan@linux.intel.com>
To: Linus Torvalds <torvalds@linux-foundation.org>,
Dan Williams <dan.j.williams@intel.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-arch@vger.kernel.org, Andi Kleen <ak@linux.intel.com>,
Kees Cook <keescook@chromium.org>,
kernel-hardening@lists.openwall.com,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
the arch/x86 maintainers <x86@kernel.org>,
Ingo Molnar <mingo@redhat.com>, Al Viro <viro@zeniv.linux.org.uk>,
"H. Peter Anvin" <hpa@zytor.com>,
Thomas Gleixner <tglx@linutronix.de>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH v3 8/9] x86: use __uaccess_begin_nospec and ASM_IFENCE in get_user paths
Date: Wed, 17 Jan 2018 14:17:26 +0000 [thread overview]
Message-ID: <1516198646.4184.13.camel@linux.intel.com> (raw)
In-Reply-To: <CA+55aFxB01XEEpdPynwYmzQMfTJdJnUrN+ZLqSV_UdnKLBgAZw@mail.gmail.com>
On Tue, 2018-01-16 at 14:41 -0800, Linus Torvalds wrote:
>
>
> On Jan 16, 2018 14:23, "Dan Williams" <dan.j.williams@intel.com>
> wrote:
> > That said, for get_user specifically, can we do something even
> > cheaper. Dave H. reminds me that any valid user pointer that gets
> > past
> > the address limit check will have the high bit clear. So instead of
> > calculating a mask, just unconditionally clear the high bit. It
> > seems
> > worse case userspace can speculatively leak something that's
> > already
> > in its address space.
>
> That's not at all true.
>
> The address may be a kernel address. That's the whole point of
> 'set_fs()'.
Can we kill off the remaining users of set_fs() ?
Alan
next prev parent reply other threads:[~2018-01-17 14:17 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-13 18:17 [PATCH v3 0/9] core, x86: prevent bounds-check bypass via speculative execution Dan Williams
2018-01-13 18:17 ` Dan Williams
2018-01-13 18:17 ` [PATCH v3 1/9] Documentation: document array_ptr Dan Williams
2018-01-13 18:17 ` Dan Williams
2018-01-13 18:17 ` [PATCH v3 2/9] arm64: implement ifence_array_ptr() Dan Williams
2018-01-13 18:17 ` [PATCH v3 3/9] arm: " Dan Williams
2018-01-13 18:17 ` Dan Williams
2018-01-13 18:17 ` [PATCH v3 4/9] x86: implement ifence() Dan Williams
2018-01-13 18:17 ` Dan Williams
2018-01-13 18:17 ` [PATCH v3 5/9] x86: implement ifence_array_ptr() and array_ptr_mask() Dan Williams
2018-01-13 18:17 ` Dan Williams
2018-01-13 18:17 ` [PATCH v3 6/9] asm/nospec: mask speculative execution flows Dan Williams
2018-01-13 18:17 ` Dan Williams
2018-01-13 18:18 ` [PATCH v3 7/9] x86: introduce __uaccess_begin_nospec and ASM_IFENCE Dan Williams
2018-01-13 18:18 ` Dan Williams
2018-01-13 18:18 ` [PATCH v3 8/9] x86: use __uaccess_begin_nospec and ASM_IFENCE in get_user paths Dan Williams
2018-01-13 18:18 ` Dan Williams
2018-01-13 19:05 ` Linus Torvalds
2018-01-13 19:33 ` Linus Torvalds
2018-01-13 20:22 ` Eric W. Biederman
2018-01-13 20:22 ` Eric W. Biederman
2018-01-16 22:23 ` Dan Williams
2018-01-16 22:23 ` Dan Williams
[not found] ` <CA+55aFxAFG5czVmCyhYMyHmXLNJ7pcXxWzusjZvLRh_qTGHj6Q@mail.gmail.com>
2018-01-16 22:41 ` Linus Torvalds
2018-01-17 14:17 ` Alan Cox [this message]
2018-01-17 18:52 ` Al Viro
2018-01-17 18:52 ` Al Viro
2018-01-17 19:54 ` Dan Williams
2018-01-17 19:54 ` Dan Williams
2018-01-17 20:05 ` Al Viro
2018-01-17 20:14 ` Dan Williams
2018-01-18 3:06 ` [RFC][PATCH] get rid of the use of set_fs() (by way of kernel_recvmsg()) in sunrpc Al Viro
2018-01-18 3:06 ` Al Viro
2018-01-18 3:16 ` Linus Torvalds
2018-01-18 3:16 ` Linus Torvalds
2018-01-18 4:43 ` Al Viro
2018-01-18 16:29 ` Christoph Hellwig
2018-01-18 16:29 ` Christoph Hellwig
2018-01-18 17:10 ` Al Viro
2018-01-18 19:31 ` Al Viro
2018-01-18 20:33 ` Al Viro
2018-01-19 3:27 ` Al Viro
2018-01-19 3:27 ` Al Viro
2018-01-17 19:26 ` [PATCH v3 8/9] x86: use __uaccess_begin_nospec and ASM_IFENCE in get_user paths Linus Torvalds
2018-01-17 20:01 ` Eric Dumazet
2018-01-17 20:01 ` Eric Dumazet
2018-01-18 16:38 ` Christoph Hellwig
2018-01-18 16:49 ` Linus Torvalds
2018-01-18 16:49 ` Linus Torvalds
2018-01-18 18:12 ` Al Viro
2018-01-17 4:30 ` Dan Williams
2018-01-17 6:28 ` Al Viro
2018-01-17 6:28 ` Al Viro
2018-01-17 6:50 ` Dan Williams
2018-01-17 6:50 ` Dan Williams
2018-01-17 10:07 ` David Laight
2018-01-17 10:07 ` David Laight
2018-01-17 18:12 ` Dan Williams
2018-01-17 19:16 ` Linus Torvalds
2018-01-17 19:16 ` Linus Torvalds
2018-01-13 18:18 ` [PATCH v3 9/9] vfs, fdtable: prevent bounds-check bypass via speculative execution Dan Williams
2018-01-13 18:18 ` Dan Williams
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