By forcing the maximum CPU that QEMU has available, we expose additional
capabilities, such as the RNDR instruction, which increases test
coverage. This then allows the CI to skip the fake seeding step in some
cases. Also enable STRICT_KERNEL_RWX to catch issues related to early
jump labels when the RNG is initialized at boot.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

With arch randomness being used by every distro and enabled in
defconfigs, the distinction between rng_has_arch_random() and
rng_is_initialized() is now rather small. In fact, the places where they
differ are now places where paranoid users and system builders really
don't want arch randomness to be used, in which case we should respect
that choice, or places where arch randomness is known to be broken, in
which case that choice is all the more important. So this commit just
removes the function and its one user.

Reviewed-by: Petr Mladek <pmladek@suse.com> # for vsprintf.c
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

This commit changes the default Kconfig values of RANDOM_TRUST_CPU and
RANDOM_TRUST_BOOTLOADER to be Y by default. It does not change any
existing configs or change any kernel behavior. The reason for this is
several fold.

As background, I recently had an email thread with the kernel
maintainers of Fedora/RHEL, Debian, Ubuntu, Gentoo, Arch, NixOS, Alpine,
SUSE, and Void as recipients. I noted that some distros trust RDRAND,
some trust EFI, and some trust both, and I asked why or why not. There
wasn't really much of a "debate" but rather an interesting discussion of
what the historical reasons have been for this, and it came up that some
distros just missed the introduction of the bootloader Kconfig knob,
while another didn't want to enable it until there was a boot time
switch to turn it off for more concerned users (which has since been
added). The result of the rather uneventful discussion is that every
major Linux distro enables these two options by default.

While I didn't have really too strong of an opinion going into this
thread -- and I mostly wanted to learn what the distros' thinking was
one way or another -- ultimately I think their choice was a decent
enough one for a default option (which can be disabled at boot time).
I'll try to summarize the pros and cons:

Pros:

- The RNG machinery gets initialized super quickly, and there's no
messing around with subsequent blocking behavior.

- The bootloader mechanism is used by kexec in order for the prior
kernel to initialize the RNG of the next kernel, which increases
the entropy available to early boot daemons of the next kernel.

- Previous objections related to backdoors centered around
Dual_EC_DRBG-like kleptographic systems, in which observing some
amount of the output stream enables an adversary holding the right key
to determine the entire output stream.

This used to be a partially justified concern, because RDRAND output
was mixed into the output stream in varying ways, some of which may
have lacked pre-image resistance (e.g. XOR or an LFSR).

But this is no longer the case. Now, all usage of RDRAND and
bootloader seeds go through a cryptographic hash function. This means
that the CPU would have to compute a hash pre-image, which is not
considered to be feasible (otherwise the hash function would be
terribly broken).

- More generally, if the CPU is backdoored, the RNG is probably not the
realistic vector of choice for an attacker.

- These CPU or bootloader seeds are far from being the only source of
entropy. Rather, there is generally a pretty huge amount of entropy,
not all of which is credited, especially on CPUs that support
instructions like RDRAND. In other words, assuming RDRAND outputs all
zeros, an attacker would *still* have to accurately model every single
other entropy source also in use.

- The RNG now reseeds itself quite rapidly during boot, starting at 2
seconds, then 4, then 8, then 16, and so forth, so that other sources
of entropy get used without much delay.

- Paranoid users can set random.trust_{cpu,bootloader}=no in the kernel
command line, and paranoid system builders can set the Kconfig options
to N, so there's no reduction or restriction of optionality.

- It's a practical default.

- All the distros have it set this way. Microsoft and Apple trust it
too. Bandwagon.

Cons:

- RDRAND *could* still be backdoored with something like a fixed key or
limited space serial number seed or another indexable scheme like
that. (However, it's hard to imagine threat models where the CPU is
backdoored like this, yet people are still okay making *any*
computations with it or connecting it to networks, etc.)

- RDRAND *could* be defective, rather than backdoored, and produce
garbage that is in one way or another insufficient for crypto.

- Suggesting a *reduction* in paranoia, as this commit effectively does,
may cause some to question my personal integrity as a "security
person".

- Bootloader seeds and RDRAND are generally very difficult if not all
together impossible to audit.

Keep in mind that this doesn't actually change any behavior. This
is just a change in the default Kconfig value. The distros already are
shipping kernels that set things this way.

Ard made an additional argument in [1]:

We're at the mercy of firmware and micro-architecture anyway, given
that we are also relying on it to ensure that every instruction in
the kernel's executable image has been faithfully copied to memory,
and that the CPU implements those instructions as documented. So I
don't think firmware or ISA bugs related to RNGs deserve special
treatment - if they are broken, we should quirk around them like we
usually do. So enabling these by default is a step in the right
direction IMHO.

In [2], Phil pointed out that having this disabled masked a bug that CI
otherwise would have caught:

A clean 5.15.45 boots cleanly, whereas a downstream kernel shows the
static key warning (but it does go on to boot). The significant
difference is that our defconfigs set CONFIG_RANDOM_TRUST_BOOTLOADER=y
defining that on top of multi_v7_defconfig demonstrates the issue on
a clean 5.15.45. Conversely, not setting that option in a
downstream kernel build avoids the warning

[1] https://lore.kernel.org/lkml/CAMj1kXGi+ieviFjXv9zQBSaGyyzeGW_VpMpTLJK8PJb2QHEQ-w@mail.gmail.com/
[2] https://lore.kernel.org/lkml/c47c42e3-1d56-5859-a6ad-976a1a3381c6@raspberrypi.com/

Cc: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

Stephen reported that a static key warning splat appears during early
boot on systems that credit randomness from device trees that contain an
"rng-seed" property, because because setup_machine_fdt() is called
before jump_label_init() during setup_arch():

static_key_enable_cpuslocked(): static key '0xffffffe51c6fcfc0' used before call to jump_label_init()
WARNING: CPU: 0 PID: 0 at kernel/jump_label.c:166 static_key_enable_cpuslocked+0xb0/0xb8
Modules linked in:
CPU: 0 PID: 0 Comm: swapper Not tainted 5.18.0+ #224 44b43e377bfc84bc99bb5ab885ff694984ee09ff
pstate: 600001c9 (nZCv dAIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : static_key_enable_cpuslocked+0xb0/0xb8
lr : static_key_enable_cpuslocked+0xb0/0xb8
sp : ffffffe51c393cf0
x29: ffffffe51c393cf0 x28: 000000008185054c x27: 00000000f1042f10
x26: 0000000000000000 x25: 00000000f10302b2 x24: 0000002513200000
x23: 0000002513200000 x22: ffffffe51c1c9000 x21: fffffffdfdc00000
x20: ffffffe51c2f0831 x19: ffffffe51c6fcfc0 x18: 00000000ffff1020
x17: 00000000e1e2ac90 x16: 00000000000000e0 x15: ffffffe51b710708
x14: 0000000000000066 x13: 0000000000000018 x12: 0000000000000000
x11: 0000000000000000 x10: 00000000ffffffff x9 : 0000000000000000
x8 : 0000000000000000 x7 : 61632065726f6665 x6 : 6220646573752027
x5 : ffffffe51c641d25 x4 : ffffffe51c13142c x3 : ffff0a00ffffff05
x2 : 40000000ffffe003 x1 : 00000000000001c0 x0 : 0000000000000065
Call trace:
static_key_enable_cpuslocked+0xb0/0xb8
static_key_enable+0x2c/0x40
crng_set_ready+0x24/0x30
execute_in_process_context+0x80/0x90
_credit_init_bits+0x100/0x154
add_bootloader_randomness+0x64/0x78
early_init_dt_scan_chosen+0x140/0x184
early_init_dt_scan_nodes+0x28/0x4c
early_init_dt_scan+0x40/0x44
setup_machine_fdt+0x7c/0x120
setup_arch+0x74/0x1d8
start_kernel+0x84/0x44c
__primary_switched+0xc0/0xc8
---[ end trace 0000000000000000 ]---
random: crng init done
Machine model: Google Lazor (rev1 - 2) with LTE

A trivial fix went in to address this on arm64, 73e2d827a501 ("arm64:
Initialize jump labels before setup_machine_fdt()"). I wrote patches as
well for arm32 and risc-v. But still patches are needed on xtensa,
powerpc, arc, and mips. So that's 7 platforms where things aren't quite
right. This sort of points to larger issues that might need a larger
solution.

Instead, this commit just defers setting the static branch until later
in the boot process. random_init() is called after jump_label_init() has
been called, and so is always a safe place from which to adjust the
static branch.

Fixes: f5bda35fba61 ("random: use static branch for crng_ready()")
Reported-by: Stephen Boyd <swboyd@chromium.org>
Reported-by: Phil Elwell <phil@raspberrypi.com>
Tested-by: Phil Elwell <phil@raspberrypi.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

Rather than accounting in bytes and multiplying (shifting), we can just
account in bits and avoid the shift. The main motivation for this is
there are other patches in flux that expand this code a bit, and
avoiding the duplication of "* 8" everywhere makes things a bit clearer.

Cc: stable@vger.kernel.org
Fixes: 12e45a2a6308 ("random: credit architectural init the exact amount")
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

add_bootloader_randomness() and the variables it touches are only used
during __init and not after, so mark these as __init. At the same time,
unexport this, since it's only called by other __init code that's
built-in.

Cc: stable@vger.kernel.org
Fixes: 428826f5358c ("fdt: add support for rng-seed")
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

The current flow expands to:

if (crng_ready())
...
else if (...)
if (!crng_ready())
...

The second crng_ready() call is redundant, but can't so easily be
optimized out by the compiler.

This commit simplifies that to:

if (crng_ready()
...
else if (...)
...

Fixes: 560181c27b58 ("random: move initialization functions out of hot pages")
Cc: stable@vger.kernel.org
Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

The code comment says that the polynomial is x^16 + x^12 + x^15 + 1, but
the correct polynomial is x^16 + x^12 + x^5 + 1. Quoting from page 2 in
the ITU-T V.41 specification [1]:

2 Encoding and checking process

The service bits and information bits, taken in conjunction,
correspond to the coefficients of a message polynomial having terms
from x^(n-1) (n = total number of bits in a block or sequence) down to
x^16. This polynomial is divided, modulo 2, by the generating
polynomial x^16 + x^12 + x^5 + 1.

The hex (truncated) polynomial 0x1021 and CRC code implementation are
correct, however.

[1] https://www.itu.int/rec/T-REC-V.41-198811-I/en

Signed-off-by: Roger Knecht <roger@norberthealth.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

Pull dma-mapping fixes from Christoph Hellwig:

- fix a regressin in setting swiotlb ->force_bounce (me)

- make dma-debug less chatty (Rob Clark)

* tag 'dma-mapping-5.19-2022-06-06' of git://git.infradead.org/users/hch/dma-mapping:
swiotlb: fix setting ->force_bounce
dma-debug: make things less spammy under memory pressure

The swiotlb_init refactor messed up assigning ->force_bounce by doing
it in different places based on what caused the setting of the flag.

Fix this by passing the SWIOTLB_* flags to swiotlb_init_io_tlb_mem
and just setting it there.

Fixes: c6af2aa9ffc9 ("swiotlb: make the swiotlb_init interface more useful")
Reported-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Nathan Chancellor <nathan@kernel.org>

Pull file descriptor fix from Al Viro:
"Fix for breakage in #work.fd this window"

* tag 'pull-work.fd-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
fix the breakage in close_fd_get_file() calling conventions change

Limit the error msg to avoid flooding the console. If you have a lot of
threads hitting this at once, they could have already gotten passed the
dma_debug_disabled() check before they get to the point of allocation
failure, resulting in quite a lot of this error message spamming the
log. Use pr_err_once() to limit that.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>