Date: Thu, 4 Mar 2021 08:37:11 +0100 From: Arrigo Marchiori <ardovm@yahoo.it> To: freebsd-stable@freebsd.org Subject: Re: Trying do mount a slice containing a r/o mounted partition makes the filesystem unreadable Message-ID: <YECOJyZHi5j558bF@nuvolo> In-Reply-To: <4ccaadf5-922f-37ee-e3f5-9f02db60516e@FreeBSD.org> References: <YDpCaI/sNgHcf08n@nuvolo> <202102271443.11REhqps070102@nuc.oldach.net> <YDpmnBNO9J4e1p4C@nuvolo> <YD3uRz5wgf9lmvPH@nuvolo> <4ccaadf5-922f-37ee-e3f5-9f02db60516e@FreeBSD.org>
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Dear All, On Tue, Mar 02, 2021 at 10:55:15AM +0200, Andriy Gapon wrote: > On 02/03/2021 09:50, Arrigo Marchiori via freebsd-stable wrote: > > Dear All, > > > > On Sat, Feb 27, 2021 at 04:34:52PM +0100, Arrigo Marchiori via freebsd-stable wrote: > > > >> Hello Helge, and thank you for replying again. > >> > >> On Sat, Feb 27, 2021 at 03:43:52PM +0100, Helge Oldach wrote: > >> > >>> Arrigo Marchiori via freebsd-stable wrote on Sat, 27 Feb 2021 14:00:24 +0100 (CET): > >>>> On the memstick, the root filesystem is mounted read-only. I > >>>> apologize, I should have told it explicitly. The ``invalid'' attempt > >>>> is to mount it read-write (no mode is indicated on the command line). > >>> > >>> Try to make it r/w mounted (which I suspect you are attempting to > >>> achieve): > >>> > >>> mount -uw / > >> > >> Ok, I will try this. > >> > >> But just for the record: I am not try to achieve anything. I gave the > >> ``invalid'' mount command by mistake (I wanted to mount a partition > >> from another disk and wrote "da0" instead of "da1") and I saw that the > >> system became unstable. I thought that this should not happen and I > >> reported it here. > > > > I have two updates. > > > > 1- the da0s2a slice starts 16 (blocks?) after the beginning of da0s2. > > bsdlabel(8) output (copied by hand): > > # /dev/da0s2: > > 8 partitions: > > # size offset fstype [fsize bsize bps/cpg] > > a: 1491200 16 4.2BSD 0 0 0 > > c: 1491216 0 unused 0 0 # "raw" part, don't edit > > > > 2- if I mount the partition rw, then the mount command _always_ fails > > with error "operation not permitted" and the system _always_ remains > > stable. This is independent from mounting from /dev/ufs/label or > > /dev/da0s2a. > > > > Therefore I can change the description of this problem report as: > > > > ----8<--------8<--------8<--------8<--------8<--------8<--------8<--------- > > > > When a BSD partition is mounted _read_only_ to / (suppose > > /dev/da0s2a), if I try to mount its containing slice (/dev/da0s2) I > > receive a ``strange'' error message, and from that moment the mounted > > filesystem becomes unreadable. > > > > - If the partition is mounted from /dev/ufs/label, then mount(8) > > reports "Operation not permitted" and the system remains stable. > > This is the expected behavior IMHO. > > > > - If the partition is mounted read_write, from any special device, > > then mount(8) reports: > > - "Operation not permitted" if I try to mount the slice rw, > > - the same strange error message if I try to mount the slice ro, > > and the system remains stable. > > > > - The "strange error message" is "invalid argument" on 11.4-STABLE. > > > > ----8<--------8<--------8<--------8<--------8<--------8<--------8<--------- > > > > Now to the question: is this worth a PR? Was it already reported? Or > > is it just something that ``should not happen'' because root should be > > allowed to shoot themselves in the foot? > > > > Thank you in advance and best regards, > > I think that this is worth a PR. Just reported: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=254005 > I think that even when mounting read-only the underlying GEOM object should be > marked for exclusive use. > I vaguely recall that UFS has some quirk in this respect to allow for > modifications by fsck. That is supposed to be limited to the root filesystem. > Maybe it should further be limited to certain boot stages to prevent > foot-shooting after a system is fully booted. Thank you and best regards, -- Arrigo http://rigo.altervista.org
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