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d=1e100.net; s=20210112; t=1679330282; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=/Dhh2AZelI4kL4AOVWhu7/w7X92iJh61WMmuzBFAiOw=; b=oh0S3cSKXIq5ij+usz6+40kheH1NgSz66s+xg3SaNx4S6C2WUg7nWlJShmAHzSjTPs ova6KWJMFTZ3SA1iVY4M2DCRF8W3+GHUMrNc3zLGM5NnvKT4PGb+UJz/6C6zlgDKTL6o lHRI6LdenSq+7krP1GkZTEmdBugusswweTW/XKtTfyRq81jbar4/UrY9JLgonqdCIdOj Wu4ovvYry++G8Iz1OmiT6FK12WRXUJCvA+rcm+66fkdlsh7S+lxifyyKOyN1Bld17U1N 7RssmHiPuUt/5PZem3jSovp+KxbZE7mksWZHPojQu/WCoxI3LMFV7ODF21P35UsNoDO8 tDCA== X-Gm-Message-State: AO0yUKU9xx3n3wlePaau3vG3+8AA2P8LxMqYrw8X1g4ytRz2XrZuIaRC HwGlJt3toENgMCNMDlkD2nH0uubwj/frPTo/Mpr3J9P0TsL10yjK X-Google-Smtp-Source: AK7set+kth7ZH+E1BmBsV7NL+CCmKvqeFcun8DqWfQLj1UGKhH+YaXB3ZhpvW3zoIeuZ2umQDnh5XGXsXKnoe81HlzY= X-Received: by 2002:a17:906:ceca:b0:92d:878e:8566 with SMTP id si10-20020a170906ceca00b0092d878e8566mr4394017ejb.10.1679330281987; Mon, 20 Mar 2023 09:38:01 -0700 (PDT) MIME-Version: 1.0 References: <5b9e31d6-2675-8903-619c-cf33c48f1ba8@gmail.com> In-Reply-To: From: lacsaP Patatetom Date: Mon, 20 Mar 2023 17:37:34 +0100 Message-ID: To: Zdenek Kabelac X-Mimecast-Impersonation-Protect: Policy=CLT - Impersonation Protection Definition; Similar Internal Domain=false; Similar Monitored External Domain=false; Custom External Domain=false; Mimecast External Domain=false; Newly Observed Domain=false; Internal User Name=false; Custom Display Name List=false; Reply-to Address Mismatch=false; Targeted Threat Dictionary=false; Mimecast Threat Dictionary=false; Custom Threat Dictionary=false X-Scanned-By: MIMEDefang 3.1 on 10.11.54.1 X-Mailman-Approved-At: Tue, 21 Mar 2023 07:54:18 +0000 Subject: Re: [linux-lvm] LVM and RO device/partition(s) X-BeenThere: linux-lvm@redhat.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: LVM general discussion and development Cc: LVM general discussion and development Errors-To: linux-lvm-bounces@redhat.com Sender: "linux-lvm" X-Scanned-By: MIMEDefang 3.1 on 10.11.54.4 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: multipart/mixed; boundary="===============2643057528223429277==" --===============2643057528223429277== Content-Type: multipart/alternative; boundary="000000000000eb20ba05f7578c6c" --000000000000eb20ba05f7578c6c Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable hi, I come back to you with the memo mentioned : https://github.com/patatetom/lvm-on-readonly-block-device I hope that it will allow you to better understand this problem of alteration of the disk. as I mentioned, LVM should normally/theoretically not touch the disk as long as it is read-only, but what bothers me the most is the fact that I can't "catch up" by correcting the new 6.1.15 kernel as I did before. regards, lacsaP. Le lun. 20 mars 2023 =C3=A0 15:15, lacsaP Patatetom a =C3=A9crit : > thank you for this first feedback. > > I am writing a memo on github and will communicate the url soon. > > my question is in the context of digital investigation which does not > admit the alteration of the medium. > of course, there are combinations (/etc/lvm.conf + snap@nbd for example) > which allow in fine not to alter the media but I don't understand why a > media set in read-only mode - eg. chmod 444 + blockdev --setro set before > LVM process - is not protected against LVM modifications... > > regards, lacsaP. > > Le lun. 20 mars 2023 =C3=A0 15:00, Zdenek Kabelac a > =C3=A9crit : > >> Dne 19. 03. 23 v 11:27 Pascal napsal(a): >> > hi, >> > >> > the bio_check_ro function of the blk-core.c source file of the Linux >> kernel >> > refers to LVM : >> > >> https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/bl= ock/blk-core.c?h=3Dv6.2.7#n500 >> < >> https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/bl= ock/blk-core.c?h=3Dv6.2.7#n500 >> > >> > >> > how does LVM currently behave when faced with a device marked as >> readonly ? >> > does it automatically switch itself in readonly mode? >> > >> > according to some tests carried out in a virtual machine, it seems tha= t >> it >> > doesn't and that LVM modifies the disk/partition(s) even though they >> are all >> > readonly (chmod 444 && blockdev --setro). >> >> >> Hi >> >> There is no extra logic around RO devices in lvm2. When lvm2 succeeds >> opening >> device in write mode, it'll use it for writing. >> >> Also note - when you 'activate' a LV in read-write mode - someone opens >> such >> LV/device and you later on 'lvchange' such active LV to read-only mode - >> all >> writers will keep writing to such device. >> >> It's not quite clear which kind of problem you are actually hitting - so >> maybe >> adding some more descriptive environment + logs might give more info >> about >> your individual case. >> >> Note: root admin typically can overwrite any 'mild' protections... >> >> Regards >> >> Zdenek >> >> --000000000000eb20ba05f7578c6c Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
hi,

I come back to you with = the memo mentioned : https://github.com/patatetom/lvm-on-readonly-block-device


Le=C2=A0lun. 20 mars 2023 =C3=A0=C2=A015:= 15, lacsaP Patatetom <patatetom@g= mail.com> a =C3=A9crit=C2=A0:
thank you for this first feedbac= k.

I am writing a memo on github and will communic= ate the url soon.

my question is in the context of digi= tal investigation which does not admit the alteration of the medium.
of course, there are combinations (/etc/lvm.conf + snap@nbd for example) = which allow in fine not to alter the media but I don't understand why a= media set in read-only mode - eg. chmod 444 + blockdev --setro set before = LVM process - is not protected against LVM modifications...

<= /div>
regards, lacsaP.

Le=C2=A0lun. 20 mars 2023 =C3=A0=C2=A01= 5:00, Zdenek Kabelac <zdenek.kabelac@gmail.com> a =C3=A9crit=C2=A0:
<= blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-l= eft:1px solid rgb(204,204,204);padding-left:1ex">Dne 19. 03. 23 v 11:27 Pas= cal napsal(a):
> hi,
>
> the bio_check_ro function of the blk-core.c source file of the Linux k= ernel
> refers to LVM :
> https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tre= e/block/blk-core.c?h=3Dv6.2.7#n500 <https://git.kernel.org/pub/scm= /linux/kernel/git/stable/linux.git/tree/block/blk-core.c?h=3Dv6.2.7#n500>
>
> how does LVM currently behave when faced with a device marked as reado= nly ?
> does it automatically switch itself in readonly mode?
>
> according to some tests carried out in a virtual machine, it seems tha= t it
> doesn't and that LVM modifies the disk/partition(s) even though th= ey are all
> readonly (chmod 444 && blockdev --setro).


Hi

There is no extra logic around RO devices in lvm2.=C2=A0 When lvm2 succeeds= opening
device in write mode, it'll use it for writing.

Also note - when you 'activate' a LV in read-write mode - someone o= pens such
LV/device and you later on 'lvchange' such active LV to read-only m= ode - all
writers will keep writing to such device.

It's not quite clear which kind of problem you are actually hitting - s= o maybe
adding some more descriptive=C2=A0 environment +=C2=A0 logs=C2=A0 might giv= e more info about
your individual case.

Note: root admin typically can overwrite any 'mild' protections...<= br>
Regards

Zdenek

--000000000000eb20ba05f7578c6c-- --===============2643057528223429277== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ linux-lvm mailing list linux-lvm@redhat.com https://listman.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/ --===============2643057528223429277==--