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Ard Biesheuvel df201eb96a efi: random: combine bootloader provided RNG seed with RNG protocol output 
commit 196dff2712 upstream.

Instead of blindly creating the EFI random seed configuration table if
the RNG protocol is implemented and works, check whether such a EFI
configuration table was provided by an earlier boot stage and if so,
concatenate the existing and the new seeds, leaving it up to the core
code to mix it in and credit it the way it sees fit.

This can be used for, e.g., systemd-boot, to pass an additional seed to
Linux in a way that can be consumed by the kernel very early. In that
case, the following definitions should be used to pass the seed to the
EFI stub:

struct linux_efi_random_seed {
      u32     size; // of the 'seed' array in bytes
      u8      seed[];
};

The memory for the struct must be allocated as EFI_ACPI_RECLAIM_MEMORY
pool memory, and the address of the struct in memory should be installed
as a EFI configuration table using the following GUID:

LINUX_EFI_RANDOM_SEED_TABLE_GUID        1ce1e5bc-7ceb-42f2-81e5-8aadf180f57b

Note that doing so is safe even on kernels that were built without this
patch applied, but the seed will simply be overwritten with a seed
derived from the EFI RNG protocol, if available. The recommended seed
size is 32 bytes, and seeds larger than 512 bytes are considered
corrupted and ignored entirely.

In order to preserve forward secrecy, seeds from previous bootloaders
are memzero'd out, and in order to preserve memory, those older seeds
are also freed from memory. Freeing from memory without first memzeroing
is not safe to do, as it's possible that nothing else will ever
overwrite those pages used by EFI.

Reviewed-by: Jason A. Donenfeld <Jason@zx2c4.com>
[ardb: incorporate Jason's followup changes to extend the maximum seed
       size on the consumer end, memzero() it and drop a needless printk]
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 		2023-01-12 12:00:48 +01:00
Documentation ext4: journal_path mount options should follow links 2023-01-07 11:16:02 +01:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
arch of/fdt: run soc memory setup when early_init_dt_scan_memory fails 2023-01-12 12:00:47 +01:00
block block: don't allow splitting of a REQ_NOWAIT bio 2023-01-12 12:00:46 +01:00
certs certs: make system keyring depend on built-in x509 parser 2022-09-24 04:31:18 +09:00
crypto crypto: tcrypt - Fix multibuffer skcipher speed test mem leak 2022-12-31 13:26:20 +01:00
drivers efi: random: combine bootloader provided RNG seed with RNG protocol output 2023-01-12 12:00:48 +01:00
fs btrfs: make thaw time super block check to also verify checksum 2023-01-12 12:00:48 +01:00
include efi: random: combine bootloader provided RNG seed with RNG protocol output 2023-01-12 12:00:48 +01:00
init init/Kconfig: fix CC_HAS_ASM_GOTO_TIED_OUTPUT test with dash 2022-12-02 17:43:11 +01:00
io_uring io_uring: fix CQ waiting timeout handling 2023-01-12 12:00:46 +01:00
ipc ipc: fix memory leak in init_mqueue_fs() 2022-12-31 13:25:48 +01:00
kernel bpf: Fix panic due to wrong pageattr of im->image 2023-01-12 12:00:45 +01:00
lib test_kprobes: Fix implicit declaration error of test_kprobes 2023-01-07 11:15:58 +01:00
mm mm, compaction: fix fast_isolate_around() to stay within boundaries 2023-01-04 11:26:30 +01:00
net 9p/client: fix data race on req->status 2023-01-12 12:00:42 +01:00
samples samples: vfio-mdev: Fix missing pci_disable_device() in mdpy_fb_probe() 2022-12-31 13:26:28 +01:00
scripts scripts/faddr2line: Fix regression in name resolution on ppc64le 2022-12-08 11:30:14 +01:00
security device_cgroup: Roll back to original exceptions after copy failure 2023-01-07 11:15:59 +01:00
sound ASoC: SOF: Intel: pci-tgl: unblock S5 entry if DMA stop has failed" 2023-01-12 12:00:44 +01:00
tools perf stat: Fix handling of --for-each-cgroup with --bpf-counters to match non BPF mode 2023-01-12 12:00:41 +01:00
usr Not a lot of material this cycle. Many singleton patches against various 2022-05-27 11:22:03 -07:00
virt KVM: Update gfn_to_pfn_cache khva when it moves within the same page 2022-12-02 17:43:13 +01:00
.clang-format inet: ping: use hlist_nulls rcu iterator during lookup 2022-12-14 11:40:58 +01:00
.cocciconfig
…
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore kbuild: split the second line of *.mod into *.usyms 2022-05-08 03:16:59 +09:00
.mailmap Qualcomm ARM64 DTS fixes for 6.0 2022-09-23 16:44:37 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS drm for 5.20/6.0 2022-08-03 19:52:08 -07:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS One MAINTAINERS update, two MM fixes, both cc:stable 2022-10-01 09:13:29 -07:00
Makefile Linux 6.0.18 2023-01-07 11:16:07 +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.