From: Linus Torvalds <torvalds@linux-foundation.org>
To: Christoph Hellwig <hch@infradead.org>
Cc: Alan Cox <alan@linux.intel.com>,
Eric Dumazet <edumazet@google.com>,
Dan Williams <dan.j.williams@intel.com>,
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: Thu, 18 Jan 2018 08:49:31 -0800 [thread overview]
Message-ID: <CA+55aFxw2CtC_28-7Renuzxfu0zegfCHv+QX-ng4NxUrBRhyXA@mail.gmail.com> (raw)
In-Reply-To: <20180118163818.GB16649@infradead.org>
On Thu, Jan 18, 2018 at 8:38 AM, Christoph Hellwig <hch@infradead.org> wrote:
>
> > But there are about ~100 set_fs() calls in generic code, and some of
> > those really are pretty fundamental. Doing things like "kernel_read()"
> > without set_fs() is basically impossible.
>
> Not if we move to iov_iter or iov_iter-like behavior for all reads
> and writes.
Not going to happen. Really. We have how many tens of thousands of
drivers again, all doing "copy_to_user()".
And the fact is, set_fs() really isn't even a problem for this. Never
really has been. From a security standpoint, it would actually be
*much* worse if we made those ten thousand places do "if (kernel_flag)
memcpy() else copy_to_user()".
We've had some issues with set_fs() being abused in interesting ways.
But "kernel_read()" and friends is not it.
Linus
next prev parent reply other threads:[~2018-01-18 16:49 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
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 [this message]
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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