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Message-ID: <20170510033911.GE390@ZenIV.linux.org.uk>
Date: Wed, 10 May 2017 04:39:12 +0100
From: Al Viro <viro@...IV.linux.org.uk>
To: Christoph Hellwig <hch@...radead.org>
Cc: Andy Lutomirski <luto@...nel.org>, Ingo Molnar <mingo@...nel.org>,
Greg KH <greg@...ah.com>, Thomas Garnier <thgarnie@...gle.com>,
Martin Schwidefsky <schwidefsky@...ibm.com>,
Heiko Carstens <heiko.carstens@...ibm.com>,
Dave Hansen <dave.hansen@...el.com>, Arnd Bergmann <arnd@...db.de>,
Thomas Gleixner <tglx@...utronix.de>,
David Howells <dhowells@...hat.com>,
René Nyffenegger <mail@...enyffenegger.ch>,
Andrew Morton <akpm@...ux-foundation.org>,
"Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
"Eric W . Biederman" <ebiederm@...ssion.com>,
Oleg Nesterov <oleg@...hat.com>,
Pavel Tikhomirov <ptikhomirov@...tuozzo.com>,
Ingo Molnar <mingo@...hat.com>, "H . Peter Anvin" <hpa@...or.com>,
Paolo Bonzini <pbonzini@...hat.com>, Rik van Riel <riel@...hat.com>,
Kees Cook <keescook@...omium.org>,
Josh Poimboeuf <jpoimboe@...hat.com>,
Borislav Petkov <bp@...en8.de>, Brian Gerst <brgerst@...il.com>,
"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
Christian Borntraeger <borntraeger@...ibm.com>,
Russell King <linux@...linux.org.uk>,
Will Deacon <will.deacon@....com>,
Catalin Marinas <catalin.marinas@....com>,
Mark Rutland <mark.rutland@....com>,
James Morse <james.morse@....com>,
linux-s390 <linux-s390@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>,
Linux API <linux-api@...r.kernel.org>,
the arch/x86 maintainers <x86@...nel.org>,
"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>,
Kernel Hardening <kernel-hardening@...ts.openwall.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: Re: [PATCH v9 1/4] syscalls: Verify address
limit before returning to user-mode
On Wed, May 10, 2017 at 04:21:37AM +0100, Al Viro wrote:
> On Wed, May 10, 2017 at 04:12:54AM +0100, Al Viro wrote:
>
> > Broken commit: "net: don't play with address limits in kernel_recvmsg".
> > It would be OK if it was only about data. Unfortunately, that's not
> > true in one case: svc_udp_recvfrom() wants ->msg_control.
> >
> > Another delicate place: you can't assume that write() always advances
> > file position by its (positive) return value. btrfs stuff is sensitive
> > to that.
> >
> > ashmem probably _is_ OK with demanding ->read_iter(), but I'm not sure
> > about blind asma->file->f_pos += ret. That's begging for races. Actually,
> > scratch that - it *is* racy.
>
> kvec_length(): please, don't. I would rather have the last remaining
> iov_length() gone... What do you need it for, anyway? You have only
> two users and both have the count passed to them (as *count and *cnt resp.)
fcntl stuff: I've decided not to put something similar into work.compat
since I couldn't decide what to do with compat stuff - word-by-word copy
from userland converting to struct flock + conversion to posix_lock +
actual work + conversion to flock + word-by-word copy to userland... Smells
like we might be better off with compat_flock_to_posix_lock() et.al.
I'm still not sure; played a bit one way and another and dediced to drop
it for now. Hell knows...
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