From: Suren Baghdasaryan <surenb@google.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: "Rasmus Villemoes" <linux@rasmusvillemoes.dk>,
"Kees Cook" <keescook@chromium.org>,
"Andrew Morton" <akpm@linux-foundation.org>,
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"Vlastimil Babka" <vbabka@suse.cz>,
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"Al Viro" <viro@zeniv.linux.org.uk>,
"Randy Dunlap" <rdunlap@infradead.org>,
"Kalesh Singh" <kaleshsingh@google.com>,
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vincenzo.frascino@arm.com,
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"Peter Collingbourne" <pcc@google.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
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"Muchun Song" <songmuchun@bytedance.com>,
"Viresh Kumar" <viresh.kumar@linaro.org>,
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LKML <linux-kernel@vger.kernel.org>,
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Subject: Re: [PATCH v8 2/3] mm: add a field to store names for private anonymous memory
Date: Tue, 31 Aug 2021 10:21:38 -0700 [thread overview]
Message-ID: <CAJuCfpEnZo8nji3R=6ek=2T2TSG=Ke22PJzV_WkYFeSV4R9beg@mail.gmail.com> (raw)
In-Reply-To: <YS0OWFnzLHJViamF@casper.infradead.org>
On Mon, Aug 30, 2021 at 9:59 AM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Mon, Aug 30, 2021 at 09:16:14AM -0700, Suren Baghdasaryan wrote:
> > On Mon, Aug 30, 2021 at 1:12 AM Rasmus Villemoes
> > <linux@rasmusvillemoes.dk> wrote:
> > >
> > > On 28/08/2021 23.47, Suren Baghdasaryan wrote:
> > > > On Fri, Aug 27, 2021 at 10:52 PM Kees Cook <keescook@chromium.org> wrote:
> > > >>
> > > >>>> + case PR_SET_VMA_ANON_NAME:
> > > >>>> + name = strndup_user((const char __user *)arg,
> > > >>>> + ANON_VMA_NAME_MAX_LEN);
> > > >>>> +
> > > >>>> + if (IS_ERR(name))
> > > >>>> + return PTR_ERR(name);
> > > >>>> +
> > > >>>> + for (pch = name; *pch != '\0'; pch++) {
> > > >>>> + if (!isprint(*pch)) {
> > > >>>> + kfree(name);
> > > >>>> + return -EINVAL;
> > > >>>
> > > >>> I think isprint() is too weak a check. For example, I would suggest
> > > >>> forbidding the following characters: ':', ']', '[', ' '. Perhaps
> > >
> > > Indeed. There's also the issue that the kernel's ctype actually
> > > implements some almost-but-not-quite latin1, so (some) chars above 0x7f
> > > would also pass isprint() - while everybody today expects utf-8, so the
> > > ability to put almost arbitrary sequences of chars with the high bit set
> > > could certainly confuse some parsers. IOW, don't use isprint() at all,
> > > just explicitly check for the byte values that we and up agreeing to
> > > allow/forbid.
> > >
> > > >>> isalnum() would be better? (permit a-zA-Z0-9) I wouldn't necessarily
> > > >>> be opposed to some punctuation characters, but let's avoid creating
> > > >>> confusion. Do you happen to know which characters are actually in use
> > > >>> today?
> > > >>
> > > >> There's some sense in refusing [, ], and :, but removing " " seems
> > > >> unhelpful for reasonable descriptors. As long as weird stuff is escaped,
> > > >> I think it's fine. Any parser can just extract with m|\[anon:(.*)\]$|
> > > >
> > > > I see no issue in forbidding '[' and ']' but whitespace and ':' are
> > > > currently used by Android. Would forbidding or escaping '[' and ']' be
> > > > enough?
> > >
> > > how about allowing [0x20, 0x7e] except [0x5b, 0x5d], i.e. all printable
> > > (including space) ascii characters, except [ \ ] - the brackets as
> > > already discussed, and backslash because then there's nobody who can get
> > > confused about whether there's some (and then which?) escaping mechanism
> > > in play - "\n" is simply never going to appear. Simple rules, easy to
> > > implement, easy to explain in a man page.
> >
> > Thanks for the suggestion, Rasmus. I'm all for keeping it simple.
> > Kees, Matthew, would that be acceptable?
>
> Yes, I think so. It permits all kinds of characters that might
> be confusing if passed on to something else, but we can't prohibit
> everything, and forbidding just these three should remove any confusion
> for any parser of /proc. Little Bobby Tables thanks you.
Thanks for all the feedback! I think I have enough change suggestions
to resping the next revision. Will send an update later today.
next prev parent reply other threads:[~2021-08-31 17:21 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-27 19:18 [PATCH v8 0/3] Anonymous VMA naming patches Suren Baghdasaryan
2021-08-27 19:18 ` [PATCH v8 1/3] mm: rearrange madvise code to allow for reuse Suren Baghdasaryan
2021-08-28 0:14 ` Kees Cook
2021-08-28 0:58 ` Suren Baghdasaryan
2021-08-28 16:19 ` Cyrill Gorcunov
2021-08-28 21:59 ` Suren Baghdasaryan
2021-08-27 19:18 ` [PATCH v8 2/3] mm: add a field to store names for private anonymous memory Suren Baghdasaryan
2021-08-28 1:47 ` Matthew Wilcox
2021-08-28 5:52 ` Kees Cook
2021-08-28 21:47 ` Suren Baghdasaryan
2021-08-30 8:12 ` Rasmus Villemoes
2021-08-30 16:16 ` Suren Baghdasaryan
2021-08-30 16:59 ` Matthew Wilcox
2021-08-31 17:21 ` Suren Baghdasaryan [this message]
2021-08-28 21:28 ` Cyrill Gorcunov
2021-08-28 21:53 ` Suren Baghdasaryan
2021-09-01 8:09 ` Michal Hocko
2021-09-01 15:28 ` Suren Baghdasaryan
2021-09-01 8:10 ` Michal Hocko
2021-09-01 15:42 ` Suren Baghdasaryan
2021-09-03 11:49 ` Michal Hocko
2021-09-03 15:47 ` Suren Baghdasaryan
2021-08-27 19:18 ` [PATCH v8 3/3] mm: add anonymous vma name refcounting Suren Baghdasaryan
2021-08-28 5:28 ` Kees Cook
2021-08-28 21:13 ` Suren Baghdasaryan
2021-08-30 7:03 ` Rolf Eike Beer
2021-08-30 16:12 ` Suren Baghdasaryan
2021-08-28 12:48 ` [PATCH v8 0/3] Anonymous VMA naming patches Pavel Machek
2021-08-28 22:06 ` Suren Baghdasaryan
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