From: Al Viro <viro@zeniv.linux.org.uk>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Jann Horn <jannh@google.com>,
baloo@gandi.net, the arch/x86 maintainers <x86@kernel.org>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
kernel list <linux-kernel@vger.kernel.org>,
Pascal Bouchareine <pascal@gandi.net>
Subject: Re: [PATCH] x86: uaccess: fix regression in unsafe_get_user
Date: Sat, 16 Feb 2019 23:47:02 +0000 [thread overview]
Message-ID: <20190216234702.GP2217@ZenIV.linux.org.uk> (raw)
In-Reply-To: <4F2693EA-1553-4F09-9475-781305540DBC@amacapital.net>
On Sat, Feb 16, 2019 at 02:50:15PM -0800, Andy Lutomirski wrote:
> What is the actual problem? We’re not actually demand-faulting this data, are we? Are we just overrunning the buffer because the from_user helpers are too clever? Can we fix it for real by having the fancy helpers do *aligned* loads so that they don’t overrun the buffer? Heck, this might be faster, too.
Unaligned _stores_ are not any cheaper, and you'd get one hell of
extra arithmetics from trying to avoid both. Check something
like e.g. memcpy() on alpha, where you really have to keep all
accesses aligned, both on load and on store side.
Can't we just pad the buffers a bit? Making sure that name_buf
and symlink_buf are _not_ followed by unmapped pages shouldn't
be hard. Both are allocated by kmalloc(), so...
What am I missing here?
next prev parent reply other threads:[~2019-02-16 23:47 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-15 23:59 [PATCH] x86: uaccess: fix regression in unsafe_get_user baloo
2019-02-16 4:20 ` Jann Horn
2019-02-16 20:18 ` Thomas Gleixner
2019-02-16 22:25 ` Thomas Gleixner
2019-02-16 22:50 ` Andy Lutomirski
2019-02-16 22:57 ` Andy Lutomirski
2019-02-16 23:47 ` Al Viro [this message]
2019-02-17 0:02 ` Al Viro
2019-02-17 2:36 ` Andy Lutomirski
2019-02-17 3:41 ` Arthur Gautier
2019-02-17 4:22 ` Al Viro
2019-02-18 13:04 ` Thomas Gleixner
2019-02-18 19:15 ` Andy Lutomirski
2019-02-18 21:13 ` Jann Horn
2019-02-18 21:51 ` Arthur Gautier
2019-09-26 9:58 ` Arthur Gautier
2019-09-26 14:09 ` Borislav Petkov
2019-10-10 16:49 ` Arthur Gautier
2019-11-05 14:11 ` Borislav Petkov
2019-11-05 16:05 ` Arthur Gautier
2019-11-06 0:21 ` Andy Lutomirski
2019-11-06 2:22 ` Arthur Gautier
2019-09-26 14:08 ` Borislav Petkov
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