From: Paul Eggert <eggert@cs.ucla.edu>
To: "Florian Weimer" <fw@deneb.enyo.de>, "Pádraig Brady" <P@draigBrady.com>
Cc: Kamil Dudka <kdudka@redhat.com>, bug-gnulib@gnu.org
Subject: Re: [PATCH] fchmodat, lchmod: port to buggy Linux filesystems
Date: Wed, 11 Mar 2020 01:03:57 -0700 [thread overview]
Message-ID: <bdced4c8-bcef-70c7-4382-b0eb6d1c7615@cs.ucla.edu> (raw)
In-Reply-To: <87o8t40zz7.fsf@mid.deneb.enyo.de>
On 3/10/20 12:30 PM, Florian Weimer wrote:
> The glibc implementation needs /proc to avoid the race. There is no
> way around that, otherwise we introduce a security vulnerability.
It is unfortunate that we have dueling paranoia here. coreutils mknod is
paranoid so it uses lchmod to avoid a race, and then glibc lchmod is paranoid so
it refuses to work with lchmod unless /proc is mounted.
Since we apparently cannot avoid a race unless /proc is mounted, I suppose we
could change gnulib lchmod to consider the current glibc behavior to be a bug,
and to fall back on lstat+chmod when /proc is not mounted. This would fix
coreutils and every other Gnulib-using program that uses lchmod or fchmodat. But
on the whole it would be somewhat cleaner if glibc lchmod and fchmodat were
merely documented to have races when /proc is not mounted; that'd be simpler
than manually adjusting all programs that use glibc lchmod so that they all
explicitly have races when /proc is not mounted.
next prev parent reply other threads:[~2020-03-11 8:04 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-13 18:42 [PATCH] fchmodat, lchmod: port to buggy Linux filesystems Paul Eggert
2020-02-14 3:29 ` Bruno Haible
2020-02-16 17:24 ` Bruno Haible
2020-02-16 18:31 ` Paul Eggert
2020-02-16 18:58 ` Bruno Haible
2020-02-14 3:46 ` Bruno Haible
2020-02-14 21:02 ` Paul Eggert
2020-02-16 21:38 ` Bruno Haible
2020-02-16 22:28 ` Bruno Haible
2020-02-22 23:46 ` Bruno Haible
2020-02-23 8:15 ` Paul Eggert
2020-02-23 10:58 ` Bruno Haible
2020-02-23 23:56 ` Paul Eggert
2020-02-24 2:27 ` overriding glibc stub functions Bruno Haible
2020-02-24 7:44 ` Paul Eggert
2020-02-23 1:35 ` [PATCH] fchmodat, lchmod: port to buggy Linux filesystems Bruno Haible
2020-02-23 7:22 ` Paul Eggert
2020-03-09 17:30 ` Pádraig Brady
2020-03-09 18:51 ` Paul Eggert
2020-03-09 23:45 ` Pádraig Brady
2020-03-10 11:52 ` Florian Weimer
2020-03-10 15:09 ` Kamil Dudka
2020-03-10 19:27 ` Pádraig Brady
2020-03-10 19:30 ` Florian Weimer
2020-03-11 8:03 ` Paul Eggert [this message]
2020-03-11 8:45 ` Florian Weimer
2020-03-11 16:04 ` Paul Eggert
2020-03-11 8:25 ` Paul Eggert
2020-03-11 8:40 ` Florian Weimer
2020-03-11 9:04 ` Kamil Dudka
2020-03-11 16:36 ` Paul Eggert
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