From: Christoph Hellwig <hch@lst.de>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Christoph Hellwig <hch@lst.de>,
the arch/x86 maintainers <x86@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Masami Hiramatsu <mhiramat@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
linux-parisc@vger.kernel.org,
linux-um <linux-um@lists.infradead.org>,
Netdev <netdev@vger.kernel.org>,
bpf@vger.kernel.org, Linux-MM <linux-mm@kvack.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 12/20] maccess: remove strncpy_from_unsafe
Date: Tue, 19 May 2020 18:41:46 +0200 [thread overview]
Message-ID: <20200519164146.GA28313@lst.de> (raw)
In-Reply-To: <CAHk-=whE_C2JF0ywF09iMBWtquEfMM3aSxCeLrb5S75EdHr1JA@mail.gmail.com>
On Tue, May 19, 2020 at 09:25:57AM -0700, Linus Torvalds wrote:
> On Tue, May 19, 2020 at 6:45 AM Christoph Hellwig <hch@lst.de> wrote:
> >
> > + if (IS_ENABLED(CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE) &&
> > + compat && (unsigned long)unsafe_ptr < TASK_SIZE)
> > + ret = strncpy_from_user_nofault(dst, user_ptr, size);
> > + else
> > + ret = strncpy_from_kernel_nofault(dst, unsafe_ptr, size);
>
> These conditionals are completely illegible.
I had a lot of folks complaining about things like:
#ifdef CONFIG_FOO
if (foo)
do_stuff();
else
#endif
do_something_else();
which I personally don't mind at all, so I switched to this style.
> static long bpf_strncpy_from_legacy(void *dest, const void
> *unsafe_ptr, long size, bool legacy)
> {
> #ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
> if (legacy && addr < TASK_SIZE)
> return strncpy_from_user_nofault(dst, (const void __user
> *) unsafe_ptr, size);
> #endif
>
> return strncpy_from_kernel_nofault(dst, unsafe_ptr, size);
> }
>
> and then you'd just use
>
> if (bpf_strncpy_from_unsafe(dst, unsafe_ptr, size, compat) < 0)
> memset(dst, 0, size);
>
> and avoid any complicated conditionals, goto's, and make the code much
> easier to understand thanks to having a big comment about the legacy
> case.
Sure.
> In fact, separately I'd probably want that "compat" naming to be
> scrapped entirely in that file.
Not my choice.. Maybe Daniel has a recommendation of what to change
there, but I'd love to not have to deal with that renaming as well
in this series.
next prev parent reply other threads:[~2020-05-19 16:41 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-19 13:44 clean up and streamline probe_kernel_* and friends v3 Christoph Hellwig
2020-05-19 13:44 ` [PATCH 01/20] maccess: unexport probe_kernel_write and probe_user_write Christoph Hellwig
2020-05-19 13:44 ` [PATCH 02/20] maccess: remove various unused weak aliases Christoph Hellwig
2020-05-19 13:44 ` [PATCH 03/20] maccess: remove duplicate kerneldoc comments Christoph Hellwig
2020-05-19 13:44 ` [PATCH 04/20] maccess: clarify " Christoph Hellwig
2020-05-19 13:44 ` [PATCH 05/20] maccess: update the top of file comment Christoph Hellwig
2020-05-19 13:44 ` [PATCH 06/20] maccess: rename strncpy_from_unsafe_user to strncpy_from_user_nofault Christoph Hellwig
2020-05-19 13:44 ` [PATCH 07/20] maccess: rename strncpy_from_unsafe_strict to strncpy_from_kernel_nofault Christoph Hellwig
2020-05-19 13:44 ` [PATCH 08/20] maccess: rename strnlen_unsafe_user to strnlen_user_nofault Christoph Hellwig
2020-05-19 13:44 ` [PATCH 09/20] maccess: remove probe_read_common and probe_write_common Christoph Hellwig
2020-05-19 13:44 ` [PATCH 10/20] maccess: unify the probe kernel arch hooks Christoph Hellwig
2020-05-19 13:44 ` [PATCH 11/20] bpf: factor out a bpf_trace_copy_string helper Christoph Hellwig
2020-05-19 16:07 ` Linus Torvalds
2020-05-19 16:14 ` Christoph Hellwig
2020-05-19 16:36 ` Linus Torvalds
2020-05-19 13:44 ` [PATCH 12/20] maccess: remove strncpy_from_unsafe Christoph Hellwig
2020-05-19 16:25 ` Linus Torvalds
2020-05-19 16:41 ` Christoph Hellwig [this message]
2020-05-19 16:46 ` Linus Torvalds
2020-05-19 13:44 ` [PATCH 13/20] maccess: always use strict semantics for probe_kernel_read Christoph Hellwig
2020-05-19 16:33 ` Linus Torvalds
2020-05-20 11:11 ` Masami Hiramatsu
2020-05-20 11:13 ` Christoph Hellwig
2020-05-19 13:44 ` [PATCH 14/20] maccess: move user access routines together Christoph Hellwig
2020-05-19 13:44 ` [PATCH 15/20] maccess: allow architectures to provide kernel probing directly Christoph Hellwig
2020-05-19 13:44 ` [PATCH 16/20] x86: use non-set_fs based maccess routines Christoph Hellwig
2020-05-19 13:44 ` [PATCH 17/20] maccess: rename probe_kernel_{read,write} to copy_{from,to}_kernel_nofault Christoph Hellwig
2020-05-19 13:44 ` [PATCH 18/20] maccess: rename probe_user_{read,write} to copy_{from,to}_user_nofault Christoph Hellwig
2020-05-19 13:44 ` [PATCH 19/20] maccess: rename probe_kernel_address to get_kernel_nofault Christoph Hellwig
2020-05-19 13:44 ` [PATCH 20/20] maccess: return -ERANGE when copy_from_kernel_nofault_allowed fails Christoph Hellwig
2020-05-20 11:02 ` Masami Hiramatsu
2020-05-20 16:16 ` Christoph Hellwig
2020-05-19 16:34 ` clean up and streamline probe_kernel_* and friends v3 Linus Torvalds
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