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[2a10:fc81:a806:d6a9::1]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-47a9de1d905sm48255782f8f.2.2026.07.08.14.31.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 08 Jul 2026 14:31:16 -0700 (PDT) From: Stefano Brivio To: Mateusz Andrzejewski Subject: Re: [PATCH v2] isolation: Add --chroot-fallback option Message-ID: <20260708233111.67e8a533@elisabeth> In-Reply-To: <20260702071526.2460400-1-mateusz.andrzejewski@mikronika.com.pl> References: <20260702071526.2460400-1-mateusz.andrzejewski@mikronika.com.pl> Organization: Red Hat X-Mailer: Claws Mail 4.2.0 (GTK 3.24.49; x86_64-pc-linux-gnu) MIME-Version: 1.0 Date: Wed, 08 Jul 2026 23:31:16 +0200 (CEST) X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: lJFOcPlaDWJEv6R9aYDeEUUxc4yJVMqVECv7GRUaWPY_1783546278 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Message-ID-Hash: MXX2NIO7GZYG6EUK7UYJUSCMTRLAZG6R X-Message-ID-Hash: MXX2NIO7GZYG6EUK7UYJUSCMTRLAZG6R X-MailFrom: sbrivio@redhat.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: passt-dev@passt.top, piotr.bzdrega@mikronika.com.pl, mateusz.andrzejewski@mikronika.com.pl X-Mailman-Version: 3.3.8 Precedence: list List-Id: Development discussion and patches for passt Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On Thu, 2 Jul 2026 09:13:31 +0200 Mateusz Andrzejewski wrote: > For integrations, which use rootfs on tmpfs or initramfs, it is not > allowed to use pivot_root(). It results with invalid argument (EINVAL) > error. Introduce --chroot-fallback option as a workaround with > MS_MOVE + chroot(). > > Due to weaker isolation of chroot() method (we don't unmount old root), > user has tu explicitly enable fallback with the new option. First, > always try to sandbox with pivot_root(). In both cases the new root is > placed into an empty tmpfs. > > For the solution to work we keep CAP_SYS_CHROOT capability, which is > dropped at the end of the isolate_prefork() function. > > Link: https://bugs.passt.top/show_bug.cgi?id=104 > > Signed-off-by: Mateusz Andrzejewski Applied (with minor tweaks as discussed), thanks, and welcome to the git log! -- Stefano