From: Christoph Hellwig <hch@lst.de>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>,
Christoph Hellwig <hch@lst.de>, Arnd Bergmann <arnd@arndb.de>,
x86@kernel.org, linux-kernel@vger.kernel.org,
Alexander Viro <viro@zeniv.linux.org.uk>,
linux-fsdevel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
linuxppc-dev@lists.ozlabs.org, Jeremy Kerr <jk@ozlabs.org>
Subject: Re: [PATCH 1/2] signal: Factor copy_siginfo_to_external32 from copy_siginfo_to_user32
Date: Sun, 19 Apr 2020 10:13:53 +0200 [thread overview]
Message-ID: <20200419081353.GF12222@lst.de> (raw)
In-Reply-To: <87v9lx3t4j.fsf@x220.int.ebiederm.org>
On Sat, Apr 18, 2020 at 06:55:56AM -0500, Eric W. Biederman wrote:
> > Is that really an issue to use that set_fs() in the coredump code ?
>
> Using set_fs() is pretty bad and something that we would like to remove
> from the kernel entirely. The fewer instances of set_fs() we have the
> better.
>
> I forget all of the details but set_fs() is both a type violation and an
> attack point when people are attacking the kernel. The existence of
> set_fs() requires somethings that should be constants to be variables.
> Something about that means that our current code is difficult to protect
> from spectre style vulnerabilities.
Yes, set_fs requires variable based address checking in the uaccess
routines for architectures with a shared address space, or even entirely
different code for architectures with separate kernel and user address
spaces. My plan is to hopefully kill set_fs in its current form a few
merge windows down the road. We'll probably still need some form of
it to e.g. mark a thread as kernel thread vs also being able to execute
user code, but it will be much ore limited than before, called from very
few places and actually be a no-op for many architectures.
next prev parent reply other threads:[~2020-04-19 8:13 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-14 7:01 remove set_fs calls from the exec and coredump code v2 Christoph Hellwig
2020-04-14 7:01 ` [PATCH 1/8] powerpc/spufs: simplify spufs core dumping Christoph Hellwig
2020-04-14 7:01 ` [PATCH 2/8] signal: clean up __copy_siginfo_to_user32 Christoph Hellwig
2020-04-17 21:08 ` Eric W. Biederman
2020-04-17 21:09 ` [PATCH 1/2] signal: Factor copy_siginfo_to_external32 from copy_siginfo_to_user32 Eric W. Biederman
2020-04-18 8:05 ` Christophe Leroy
2020-04-18 11:55 ` Eric W. Biederman
2020-04-19 8:13 ` Christoph Hellwig [this message]
2020-04-19 9:46 ` Christophe Leroy
2020-04-19 9:54 ` Christophe Leroy
2020-04-19 8:05 ` Christoph Hellwig
2020-04-17 21:09 ` [PATCH 2/2] signal: Remove the set_fs in binfmt_elf.c:fill_siginfo_note Eric W. Biederman
2020-04-19 8:03 ` [PATCH 2/8] signal: clean up __copy_siginfo_to_user32 Christoph Hellwig
2020-04-14 7:01 ` [PATCH 3/8] signal: replace __copy_siginfo_to_user32 with to_compat_siginfo Christoph Hellwig
2020-04-14 14:00 ` Arnd Bergmann
2020-04-14 7:01 ` [PATCH 4/8] binfmt_elf: open code copy_siginfo_to_user to kernelspace buffer Christoph Hellwig
2020-04-14 13:15 ` Arnd Bergmann
2020-04-15 7:45 ` Christoph Hellwig
2020-04-15 8:20 ` Arnd Bergmann
2020-04-17 13:27 ` Christoph Hellwig
2020-04-17 18:10 ` Eric W. Biederman
2020-04-17 20:06 ` Arnd Bergmann
2020-04-15 3:01 ` Michael Ellerman
2020-04-15 6:19 ` Christoph Hellwig
2020-04-14 7:01 ` [PATCH 5/8] binfmt_elf: remove the set_fs(KERNEL_DS) in elf_core_dump Christoph Hellwig
2020-04-14 7:01 ` [PATCH 6/8] binfmt_elf_fdpic: remove the set_fs(KERNEL_DS) in elf_fdpic_core_dump Christoph Hellwig
2020-04-14 7:01 ` [PATCH 7/8] exec: simplify the copy_strings_kernel calling convention Christoph Hellwig
2020-04-14 7:01 ` [PATCH 8/8] exec: open code copy_string_kernel Christoph Hellwig
2020-04-18 8:15 ` Christophe Leroy
2020-04-19 8:06 ` Christoph Hellwig
2020-04-19 9:44 ` Christophe Leroy
2020-04-17 22:41 ` remove set_fs calls from the exec and coredump code v2 Eric W. Biederman
2020-04-19 8:19 ` Christoph Hellwig
2020-04-19 11:50 ` Eric W. Biederman
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