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Milan Broz 12caa73a28 dm-verity FEC: Fix RS FEC repair for roots unaligned to block size (take 2) 
commit 6df90c02ba upstream.

This patch fixes an issue that was fixed in the commit
  df7b59ba92 ("dm verity: fix FEC for RS roots unaligned to block size")
but later broken again in the commit
  8ca7cab82b ("dm verity fec: fix misaligned RS roots IO")

If the Reed-Solomon roots setting spans multiple blocks, the code does not
use proper parity bytes and randomly fails to repair even trivial errors.

This bug cannot happen if the sector size is multiple of RS roots
setting (Android case with roots 2).

The previous solution was to find a dm-bufio block size that is multiple
of the device sector size and roots size. Unfortunately, the optimization
in commit 8ca7cab82b ("dm verity fec: fix misaligned RS roots IO")
is incorrect and uses data block size for some roots (for example, it uses
4096 block size for roots = 20).

This patch uses a different approach:

 - It always uses a configured data block size for dm-bufio to avoid
 possible misaligned IOs.

 - and it caches the processed parity bytes, so it can join it
 if it spans two blocks.

As the RS calculation is called only if an error is detected and
the process is computationally intensive, copying a few more bytes
should not introduce performance issues.

The issue was reported to cryptsetup with trivial reproducer
  https://gitlab.com/cryptsetup/cryptsetup/-/issues/923

Reproducer (with roots=20):

 # create verity device with RS FEC
 dd if=/dev/urandom of=data.img bs=4096 count=8 status=none
 veritysetup format data.img hash.img --fec-device=fec.img --fec-roots=20 | \
 awk '/^Root hash/{ print $3 }' >roothash

 # create an erasure that should always be repairable with this roots setting
 dd if=/dev/zero of=data.img conv=notrunc bs=1 count=4 seek=4 status=none

 # try to read it through dm-verity
 veritysetup open data.img test hash.img --fec-device=fec.img --fec-roots=20 $(cat roothash)
 dd if=/dev/mapper/test of=/dev/null bs=4096 status=noxfer

 Even now the log says it cannot repair it:
   : verity-fec: 7:1: FEC 0: failed to correct: -74
   : device-mapper: verity: 7:1: data block 0 is corrupted
   ...

With this fix, errors are properly repaired.
   : verity-fec: 7:1: FEC 0: corrected 4 errors

Signed-off-by: Milan Broz <gmazyland@gmail.com>
Fixes: 8ca7cab82b ("dm verity fec: fix misaligned RS roots IO")
Cc: stable@vger.kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Milan Broz <gmazyland@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2025-01-17 13:36:19 +01:00
arch riscv: Fix sleeping in invalid context in die() 2025-01-17 13:36:18 +01:00
block block: avoid to reuse hctx not removed from cpuhp callback list 2025-01-02 10:32:11 +01:00
certs certs: Reference revocation list for all keyrings 2023-08-17 20:12:41 +00:00
crypto crypto: ecc - Prevent ecc_digits_from_bytes from reading too many bytes 2025-01-09 13:31:52 +01:00
Documentation dt-bindings: display: adi,adv7533: Drop single lane support 2025-01-09 13:32:08 +01:00
drivers dm-verity FEC: Fix RS FEC repair for roots unaligned to block size (take 2) 2025-01-17 13:36:19 +01:00
fs f2fs: fix null-ptr-deref in f2fs_submit_page_bio() 2025-01-17 13:36:19 +01:00
include scsi: ufs: qcom: Power off the PHY if it was already powered on in ufs_qcom_power_up_sequence() 2025-01-17 13:36:17 +01:00
init Compiler Attributes: disable __counted_by for clang < 19.1.3 2024-12-09 10:32:46 +01:00
io_uring io_uring/timeout: fix multishot updates 2025-01-17 13:36:19 +01:00
ipc ipc: fix memleak if msg_init_ns failed in create_ipc_ns 2024-12-09 10:32:54 +01:00
kernel kcov: mark in_softirq_really() as __always_inline 2025-01-09 13:32:07 +01:00
lib seq_buf: Introduce DECLARE_SEQ_BUF and seq_buf_str() 2025-01-09 13:31:55 +01:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm memblock: use numa_valid_node() helper to check for invalid node ID 2025-01-17 13:36:09 +01:00
net sctp: sysctl: plpmtud_probe_interval: avoid using current->nsproxy 2025-01-17 13:36:18 +01:00
rust rust: macros: fix documentation of the paste! macro 2024-12-09 10:32:25 +01:00
samples samples/bpf: Fix a resource leak 2024-12-14 20:00:03 +01:00
scripts scripts/sorttable: fix orc_sort_cmp() to maintain symmetry and transitivity 2025-01-09 13:32:07 +01:00
security selinux: ignore unknown extended permissions 2025-01-09 13:31:54 +01:00
sound ASoC: mediatek: disable buffer pre-allocation 2025-01-17 13:36:11 +01:00
tools memblock tests: fix implicit declaration of function 'numa_valid_node' 2025-01-17 13:36:14 +01:00
usr initramfs: Encode dependency on KBUILD_BUILD_TIMESTAMP 2023-06-06 17:54:49 +09:00
virt KVM: Use dedicated mutex to protect kvm_usage_count to avoid deadlock 2024-10-04 16:29:47 +02:00
.clang-format iommu: Add for_each_group_device() 2023-05-23 08:15:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore Remove *.orig pattern from .gitignore 2024-10-04 16:29:44 +02:00
.mailmap 20 hotfixes. 12 are cc:stable and the remainder address post-6.5 issues 2023-10-24 09:52:16 -10:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS USB: Remove Wireless USB and UWB documentation 2023-08-09 14:17:32 +02:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS membarrier: riscv: Add full memory barrier in switch_mm() 2024-09-12 11:11:45 +02:00
Makefile Linux 6.6.71 2025-01-10 14:31:36 +01:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.