From: Christoph Hellwig <hch@lst.de>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>, Kees Cook <keescook@chromium.org>,
Iurii Zaikin <yzaikin@google.com>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
linux-fsdevel@vger.kernel.org, netdev@vger.kernel.org,
bpf@vger.kernel.org
Subject: Re: [PATCH 5/5] sysctl: pass kernel pointers to ->proc_handler
Date: Wed, 22 Apr 2020 08:09:22 +0200 [thread overview]
Message-ID: <20200422060922.GA22775@lst.de> (raw)
In-Reply-To: <20200422024626.GI23230@ZenIV.linux.org.uk>
On Wed, Apr 22, 2020 at 03:46:26AM +0100, Al Viro wrote:
> > Better allocate count + 1 bytes here, that way a lot of insanity in the
> > instances can be simply converted to snprintf(). Yes, I know it'll bring
> > the Church Of Avoiding The Abomination Of Sprintf out of the woodwork,
> > but...
>
> FWIW, consider e.g. net/sunrpc/sysctl.c:
>
> Nevermind that the read side should be simply
> int err = proc_douintvec(table, write, buffer, lenp, ppos);
> /* Display the RPC tasks on writing to rpc_debug */
> if (!err && strcmp(table->procname, "rpc_debug") == 0)
> rpc_show_tasks(&init_net);
> return err;
> the write side would become
> len = snprintf(buffer, *lenp + 1, "0x%04x\n",
> *(unsigned int *)table->data);
> if (len > *lenp)
> len = *lenp;
> *lenp -= len;
> *ppos += len;
> return 0;
> and I really wonder if lifting the trailing boilerplate into the caller would've
> been better. Note that e.g. gems like
> if (!first)
> err = proc_put_char(&buffer, &left, '\t');
> if (err)
> break;
> err = proc_put_long(&buffer, &left, lval, neg);
> if (err)
> break;
> are due to lack of snprintf-to-user; now, lose the "to user" part and we suddenly
> can be rid of that stuff...
That sounds pretty sensible, but can we do that as an extra step?
That is in merge window N just move to passing kernel pointers, check
for fall out. In merge window N + 1 start allocatin the extra byte and
switch at least the common helpers for snprintf?
next prev parent reply other threads:[~2020-04-22 6:09 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-21 17:15 pass kernel pointers to the sysctl ->proc_handler method v2 Christoph Hellwig
2020-04-21 17:15 ` [PATCH 1/5] bpf-cgroup: remove unused exports Christoph Hellwig
2020-04-22 23:39 ` Andrey Ignatov
2020-04-21 17:15 ` [PATCH 2/5] mm: remove watermark_boost_factor_sysctl_handler Christoph Hellwig
2020-04-21 19:31 ` David Rientjes
2020-04-21 17:15 ` [PATCH 3/5] sysctl: remove all extern declaration from sysctl.c Christoph Hellwig
2020-04-22 10:30 ` Vlastimil Babka
2020-04-22 17:24 ` Christoph Hellwig
2020-04-21 17:15 ` [PATCH 4/5] sysctl: avoid forward declarations Christoph Hellwig
2020-04-21 17:15 ` [PATCH 5/5] sysctl: pass kernel pointers to ->proc_handler Christoph Hellwig
2020-04-21 19:16 ` Al Viro
2020-04-22 2:46 ` Al Viro
2020-04-22 6:09 ` Christoph Hellwig [this message]
2020-04-21 19:23 ` Andrey Ignatov
2020-04-22 17:22 ` Christoph Hellwig
2020-04-22 23:40 ` Andrey Ignatov
2020-04-24 6:43 pass kernel pointers to the sysctl ->proc_handler method v3 Christoph Hellwig
2020-04-24 6:43 ` [PATCH 5/5] sysctl: pass kernel pointers to ->proc_handler Christoph Hellwig
2020-04-24 19:06 ` Andrey Ignatov
2020-04-27 5:34 ` Christoph Hellwig
2020-05-04 19:01 ` Kees Cook
2020-05-05 5:57 ` Christoph Hellwig
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