Verity targets can be configured to ignore corrupted data blocks.
LoadPin must only trust verity targets that are configured to
perform some kind of enforcement when data corruption is detected,
like returning an error, restarting the system or triggering a
panic.
Fixes: b6c1c5745c ("dm: Add verity helpers for LoadPin")
Reported-by: Sarthak Kukreti <sarthakkukreti@chromium.org>
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Reviewed-by: Sarthak Kukreti <sarthakkukreti@chromium.org>
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220907133055.1.Ic8a1dafe960dc0f8302e189642bc88ebb785d274@changeid
DM_BUFIO_CLIENT_NO_SLEEP flag to have dm-bufio use spinlock rather
than mutex for its locking.
- Add optional "try_verify_in_tasklet" feature to DM verity target.
This feature gives users the option to improve IO latency by using a
tasklet to verify, using hashes in bufio's cache, rather than wait
to schedule a work item via workqueue. But if there is a bufio cache
miss, or an error, then the tasklet will fallback to using workqueue.
- Incremental changes to both dm-bufio and the DM verity target to use
jump_label to minimize cost of branching associated with the niche
"try_verify_in_tasklet" feature. DM-bufio in particular is used by
quite a few other DM targets so it doesn't make sense to incur
additional bufio cost in those targets purely for the benefit of
this niche verity feature if the feature isn't ever used.
- Optimize verity_verify_io, which is used by both workqueue and
tasklet based verification, if FEC is not configured or tasklet
based verification isn't used.
- Remove DM verity target's verify_wq's use of the WQ_CPU_INTENSIVE
flag since it uses WQ_UNBOUND. Also, use the WQ_HIGHPRI flag if
"try_verify_in_tasklet" is specified.
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Merge tag 'for-6.0/dm-changes-2' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm
Pull more device mapper updates from Mike Snitzer:
- Add flags argument to dm_bufio_client_create and introduce
DM_BUFIO_CLIENT_NO_SLEEP flag to have dm-bufio use spinlock rather
than mutex for its locking.
- Add optional "try_verify_in_tasklet" feature to DM verity target.
This feature gives users the option to improve IO latency by using a
tasklet to verify, using hashes in bufio's cache, rather than wait to
schedule a work item via workqueue. But if there is a bufio cache
miss, or an error, then the tasklet will fallback to using workqueue.
- Incremental changes to both dm-bufio and the DM verity target to use
jump_label to minimize cost of branching associated with the niche
"try_verify_in_tasklet" feature. DM-bufio in particular is used by
quite a few other DM targets so it doesn't make sense to incur
additional bufio cost in those targets purely for the benefit of this
niche verity feature if the feature isn't ever used.
- Optimize verity_verify_io, which is used by both workqueue and
tasklet based verification, if FEC is not configured or tasklet based
verification isn't used.
- Remove DM verity target's verify_wq's use of the WQ_CPU_INTENSIVE
flag since it uses WQ_UNBOUND. Also, use the WQ_HIGHPRI flag if
"try_verify_in_tasklet" is specified.
* tag 'for-6.0/dm-changes-2' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm:
dm verity: have verify_wq use WQ_HIGHPRI if "try_verify_in_tasklet"
dm verity: remove WQ_CPU_INTENSIVE flag since using WQ_UNBOUND
dm verity: only copy bvec_iter in verity_verify_io if in_tasklet
dm verity: optimize verity_verify_io if FEC not configured
dm verity: conditionally enable branching for "try_verify_in_tasklet"
dm bufio: conditionally enable branching for DM_BUFIO_CLIENT_NO_SLEEP
dm verity: allow optional args to alter primary args handling
dm verity: Add optional "try_verify_in_tasklet" feature
dm bufio: Add DM_BUFIO_CLIENT_NO_SLEEP flag
dm bufio: Add flags argument to dm_bufio_client_create
Using tasklets for disk verification can reduce IO latency. When there
are accelerated hash instructions it is often better to compute the
hash immediately using a tasklet rather than deferring verification to
a work-queue. This reduces time spent waiting to schedule work-queue
jobs, but requires spending slightly more time in interrupt context.
If the dm-bufio cache does not have the required hashes we fallback to
the work-queue implementation. FEC is only possible using work-queue
because code to support the FEC feature may sleep.
The following shows a speed comparison of random reads on a dm-verity
device. The dm-verity device uses a 1G ramdisk for data and a 1G
ramdisk for hashes. One test was run using tasklets and one test was
run using the existing work-queue solution. Both tests were run when
the dm-bufio cache was hot. The tasklet implementation performs
significantly better since there is no time spent waiting for
work-queue jobs to be scheduled.
READ: bw=181MiB/s (190MB/s), 181MiB/s-181MiB/s (190MB/s-190MB/s),
io=512MiB (537MB), run=2827-2827msec
READ: bw=23.6MiB/s (24.8MB/s), 23.6MiB/s-23.6MiB/s (24.8MB/s-24.8MB/s),
io=512MiB (537MB), run=21688-21688msec
Signed-off-by: Nathan Huckleberry <nhuck@google.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
LoadPin limits loading of kernel modules, firmware and certain
other files to a 'pinned' file system (typically a read-only
rootfs). To provide more flexibility LoadPin is being extended
to also allow loading these files from trusted dm-verity
devices. For that purpose LoadPin can be provided with a list
of verity root digests that it should consider as trusted.
Add a bunch of helpers to allow LoadPin to check whether a DM
device is a trusted verity device. The new functions broadly
fall in two categories: those that need access to verity
internals (like the root digest), and the 'glue' between
LoadPin and verity. The new file dm-verity-loadpin.c contains
the glue functions.
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Acked-by: Mike Snitzer <snitzer@kernel.org>
Link: https://lore.kernel.org/lkml/20220627083512.v7.1.I3e928575a23481121e73286874c4c2bdb403355d@changeid
Signed-off-by: Kees Cook <keescook@chromium.org>
Samsung smart phones may need the ability to panic on corruption. Not
all devices provide the bootloader support needed to use the existing
"restart_on_corruption" mode. Additional details for why Samsung needs
this new mode can be found here:
https://www.redhat.com/archives/dm-devel/2020-June/msg00235.html
Signed-off-by: jhs2.lee <jhs2.lee@samsung.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
The verification is to support cases where the root hash is not secured
by Trusted Boot, UEFI Secureboot or similar technologies.
One of the use cases for this is for dm-verity volumes mounted after
boot, the root hash provided during the creation of the dm-verity volume
has to be secure and thus in-kernel validation implemented here will be
used before we trust the root hash and allow the block device to be
created.
The signature being provided for verification must verify the root hash
and must be trusted by the builtin keyring for verification to succeed.
The hash is added as a key of type "user" and the description is passed
to the kernel so it can look it up and use it for verification.
Adds CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG which can be turned on if root
hash verification is needed.
Kernel commandline dm_verity module parameter 'require_signatures' will
indicate whether to force root hash signature verification (for all dm
verity volumes).
Signed-off-by: Jaskaran Khurana <jaskarankhurana@linux.microsoft.com>
Tested-and-Reviewed-by: Milan Broz <gmazyland@gmail.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Based on 1 normalized pattern(s):
this file is released under the gplv2
extracted by the scancode license scanner the SPDX license identifier
GPL-2.0-only
has been chosen to replace the boilerplate/reference in 68 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Armijn Hemel <armijn@tjaldur.nl>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190531190114.292346262@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This allows platforms that are CPU/memory contrained to verify data
blocks only the first time they are read from the data device, rather
than every time. As such, it provides a reduced level of security
because only offline tampering of the data device's content will be
detected, not online tampering.
Hash blocks are still verified each time they are read from the hash
device, since verification of hash blocks is less performance critical
than data blocks, and a hash block will not be verified any more after
all the data blocks it covers have been verified anyway.
This option introduces a bitset that is used to check if a block has
been validated before or not. A block can be validated more than once
as there is no thread protection for the bitset.
These changes were developed and tested on entry-level Android Go
devices.
Signed-off-by: Patrik Torstensson <totte@google.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Move dm-bufio.h to include/linux/ so that external GPL'd DM target
modules can use it.
It is better to allow the use of dm-bufio than force external modules
to implement the equivalent buffered IO mechanism in some new way. The
hope is this will encourage the use of dm-bufio; which will then make it
easier for a GPL'd external DM target module to be included upstream.
A couple dm-bufio EXPORT_SYMBOL exports have also been updated to use
EXPORT_SYMBOL_GPL.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
dm-verity is starting async. crypto ops and waiting for them to complete.
Move it over to generic code doing the same.
This also avoids a future potential data coruption bug created
by the use of wait_for_completion_interruptible() without dealing
correctly with an interrupt aborting the wait prior to the
async op finishing, should this code ever move to a context
where signals are not masked.
Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com>
CC: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Use of the synchronous digest API limits dm-verity to using pure
CPU based algorithm providers and rules out the use of off CPU
algorithm providers which are normally asynchronous by nature,
potentially freeing CPU cycles.
This can reduce performance per Watt in situations such as during
boot time when a lot of concurrent file accesses are made to the
protected volume.
Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com>
CC: Eric Biggers <ebiggers3@gmail.com>
CC: Ondrej Mosnáček <omosnacek+linux-crypto@gmail.com>
Tested-by: Milan Broz <gmazyland@gmail.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
If ignore_zero_blocks is enabled dm-verity will return zeroes for blocks
matching a zero hash without validating the content.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Add support for correcting corrupted blocks using Reed-Solomon.
This code uses RS(255, N) interleaved across data and hash
blocks. Each error-correcting block covers N bytes evenly
distributed across the combined total data, so that each byte is a
maximum distance away from the others. This makes it possible to
recover from several consecutive corrupted blocks with relatively
small space overhead.
In addition, using verity hashes to locate erasures nearly doubles
the effectiveness of error correction. Being able to detect
corrupted blocks also improves performance, because only corrupted
blocks need to corrected.
For a 2 GiB partition, RS(255, 253) (two parity bytes for each
253-byte block) can correct up to 16 MiB of consecutive corrupted
blocks if erasures can be located, and 8 MiB if they cannot, with
16 MiB space overhead.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
verity_for_bv_block() will be re-used by optional dm-verity object.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Prepare for an optional verity object to make use of existing dm-verity
structures and functions.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
