This patch changes the read semantics of /dev/random to be the same
as /dev/urandom except that reads will block until the CRNG is
ready.
None of the cleanups that this enables have been done yet. As a
result, this gives a warning about an unused function.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/5e6ac8831c6cf2e56a7a4b39616d1732b2bdd06c.1577088521.git.luto@kernel.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
The separate blocking pool is going away. Start by ignoring
GRND_RANDOM in getentropy(2).
This should not materially break any API. Any code that worked
without this change should work at least as well with this change.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/705c5a091b63cc5da70c99304bb97e0109be0a26.1577088521.git.luto@kernel.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
/dev/random and getrandom() never warn. Split the meat of
urandom_read() into urandom_read_nowarn() and leave the warning code
in urandom_read().
This has no effect on kernel behavior, but it makes subsequent
patches more straightforward. It also makes the fact that
getrandom() never warns more obvious.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/c87ab200588de746431d9f916501ef11e5242b13.1577088521.git.luto@kernel.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Recently, there's been some compat ioctl cleanup, in which large
hardcoded lists were replaced with compat_ptr_ioctl. One of these
changes involved removing the random.c hardcoded list entries and adding
a compat ioctl function pointer to the random.c fops. In the process,
urandom was forgotten about, so this commit fixes that oversight.
Fixes: 507e4e2b43 ("compat_ioctl: remove /dev/random commands")
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Link: https://lore.kernel.org/r/20191217172455.186395-1-Jason@zx2c4.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
As part of the cleanup of some remaining y2038 issues, I came to
fs/compat_ioctl.c, which still has a couple of commands that need support
for time64_t.
In completely unrelated work, I spent time on cleaning up parts of this
file in the past, moving things out into drivers instead.
After Al Viro reviewed an earlier version of this series and did a lot
more of that cleanup, I decided to try to completely eliminate the rest
of it and move it all into drivers.
This series incorporates some of Al's work and many patches of my own,
but in the end stops short of actually removing the last part, which is
the scsi ioctl handlers. I have patches for those as well, but they need
more testing or possibly a rewrite.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
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Merge tag 'compat-ioctl-5.5' of git://git.kernel.org:/pub/scm/linux/kernel/git/arnd/playground
Pull removal of most of fs/compat_ioctl.c from Arnd Bergmann:
"As part of the cleanup of some remaining y2038 issues, I came to
fs/compat_ioctl.c, which still has a couple of commands that need
support for time64_t.
In completely unrelated work, I spent time on cleaning up parts of
this file in the past, moving things out into drivers instead.
After Al Viro reviewed an earlier version of this series and did a lot
more of that cleanup, I decided to try to completely eliminate the
rest of it and move it all into drivers.
This series incorporates some of Al's work and many patches of my own,
but in the end stops short of actually removing the last part, which
is the scsi ioctl handlers. I have patches for those as well, but they
need more testing or possibly a rewrite"
* tag 'compat-ioctl-5.5' of git://git.kernel.org:/pub/scm/linux/kernel/git/arnd/playground: (42 commits)
scsi: sd: enable compat ioctls for sed-opal
pktcdvd: add compat_ioctl handler
compat_ioctl: move SG_GET_REQUEST_TABLE handling
compat_ioctl: ppp: move simple commands into ppp_generic.c
compat_ioctl: handle PPPIOCGIDLE for 64-bit time_t
compat_ioctl: move PPPIOCSCOMPRESS to ppp_generic
compat_ioctl: unify copy-in of ppp filters
tty: handle compat PPP ioctls
compat_ioctl: move SIOCOUTQ out of compat_ioctl.c
compat_ioctl: handle SIOCOUTQNSD
af_unix: add compat_ioctl support
compat_ioctl: reimplement SG_IO handling
compat_ioctl: move WDIOC handling into wdt drivers
fs: compat_ioctl: move FITRIM emulation into file systems
gfs2: add compat_ioctl support
compat_ioctl: remove unused convert_in_user macro
compat_ioctl: remove last RAID handling code
compat_ioctl: remove /dev/raw ioctl translation
compat_ioctl: remove PCI ioctl translation
compat_ioctl: remove joystick ioctl translation
...
Pull crypto fix from Herbert Xu:
"This reverts a number of changes to the khwrng thread which feeds the
kernel random number pool from hwrng drivers. They were trying to fix
issues with suspend-and-resume but ended up causing regressions"
* 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6:
Revert "hwrng: core - Freeze khwrng thread during suspend"
This reverts commit 03a3bb7ae6 ("hwrng: core - Freeze khwrng
thread during suspend"), ff296293b3 ("random: Support freezable
kthreads in add_hwgenerator_randomness()") and 59b569480d ("random:
Use wait_event_freezable() in add_hwgenerator_randomness()").
These patches introduced regressions and we need more time to
get them ready for mainline.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
These are all handled by the random driver, so instead of listing
each ioctl, we can use the generic compat_ptr_ioctl() helper.
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
On Tue, Oct 01, 2019 at 10:14:40AM -0700, Linus Torvalds wrote:
> The previous state of the file didn't have that 0xa at the end, so you get that
>
>
> -EXPORT_SYMBOL_GPL(add_bootloader_randomness);
> \ No newline at end of file
> +EXPORT_SYMBOL_GPL(add_bootloader_randomness);
>
> which is "the '-' line doesn't have a newline, the '+' line does" marker.
Aaha, that makes total sense, thanks for explaining. Oh well, let's fix
it then so that people don't scratch heads like me.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Merge active entropy generation updates.
This is admittedly partly "for discussion". We need to have a way
forward for the boot time deadlocks where user space ends up waiting for
more entropy, but no entropy is forthcoming because the system is
entirely idle just waiting for something to happen.
While this was triggered by what is arguably a user space bug with
GDM/gnome-session asking for secure randomness during early boot, when
they didn't even need any such truly secure thing, the issue ends up
being that our "getrandom()" interface is prone to that kind of
confusion, because people don't think very hard about whether they want
to block for sufficient amounts of entropy.
The approach here-in is to decide to not just passively wait for entropy
to happen, but to start actively collecting it if it is missing. This
is not necessarily always possible, but if the architecture has a CPU
cycle counter, there is a fair amount of noise in the exact timings of
reasonably complex loads.
We may end up tweaking the load and the entropy estimates, but this
should be at least a reasonable starting point.
As part of this, we also revert the revert of the ext4 IO pattern
improvement that ended up triggering the reported lack of external
entropy.
* getrandom() active entropy waiting:
Revert "Revert "ext4: make __ext4_get_inode_loc plug""
random: try to actively add entropy rather than passively wait for it
For 5.3 we had to revert a nice ext4 IO pattern improvement, because it
caused a bootup regression due to lack of entropy at bootup together
with arguably broken user space that was asking for secure random
numbers when it really didn't need to.
See commit 72dbcf7215 (Revert "ext4: make __ext4_get_inode_loc plug").
This aims to solve the issue by actively generating entropy noise using
the CPU cycle counter when waiting for the random number generator to
initialize. This only works when you have a high-frequency time stamp
counter available, but that's the case on all modern x86 CPU's, and on
most other modern CPU's too.
What we do is to generate jitter entropy from the CPU cycle counter
under a somewhat complex load: calling the scheduler while also
guaranteeing a certain amount of timing noise by also triggering a
timer.
I'm sure we can tweak this, and that people will want to look at other
alternatives, but there's been a number of papers written on jitter
entropy, and this should really be fairly conservative by crediting one
bit of entropy for every timer-induced jump in the cycle counter. Not
because the timer itself would be all that unpredictable, but because
the interaction between the timer and the loop is going to be.
Even if (and perhaps particularly if) the timer actually happens on
another CPU, the cacheline interaction between the loop that reads the
cycle counter and the timer itself firing is going to add perturbations
to the cycle counter values that get mixed into the entropy pool.
As Thomas pointed out, with a modern out-of-order CPU, even quite simple
loops show a fair amount of hard-to-predict timing variability even in
the absense of external interrupts. But this tries to take that further
by actually having a fairly complex interaction.
This is not going to solve the entropy issue for architectures that have
no CPU cycle counter, but it's not clear how (and if) that is solvable,
and the hardware in question is largely starting to be irrelevant. And
by doing this we can at least avoid some of the even more contentious
approaches (like making the entropy waiting time out in order to avoid
the possibly unbounded waiting).
Cc: Ahmed Darwish <darwish.07@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Nicholas Mc Guire <hofrat@opentech.at>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Willy Tarreau <w@1wt.eu>
Cc: Alexander E. Patrakov <patrakov@gmail.com>
Cc: Lennart Poettering <mzxreary@0pointer.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull crypto updates from Herbert Xu:
"API:
- Add the ability to abort a skcipher walk.
Algorithms:
- Fix XTS to actually do the stealing.
- Add library helpers for AES and DES for single-block users.
- Add library helpers for SHA256.
- Add new DES key verification helper.
- Add surrounding bits for ESSIV generator.
- Add accelerations for aegis128.
- Add test vectors for lzo-rle.
Drivers:
- Add i.MX8MQ support to caam.
- Add gcm/ccm/cfb/ofb aes support in inside-secure.
- Add ofb/cfb aes support in media-tek.
- Add HiSilicon ZIP accelerator support.
Others:
- Fix potential race condition in padata.
- Use unbound workqueues in padata"
* 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6: (311 commits)
crypto: caam - Cast to long first before pointer conversion
crypto: ccree - enable CTS support in AES-XTS
crypto: inside-secure - Probe transform record cache RAM sizes
crypto: inside-secure - Base RD fetchcount on actual RD FIFO size
crypto: inside-secure - Base CD fetchcount on actual CD FIFO size
crypto: inside-secure - Enable extended algorithms on newer HW
crypto: inside-secure: Corrected configuration of EIP96_TOKEN_CTRL
crypto: inside-secure - Add EIP97/EIP197 and endianness detection
padata: remove cpu_index from the parallel_queue
padata: unbind parallel jobs from specific CPUs
padata: use separate workqueues for parallel and serial work
padata, pcrypt: take CPU hotplug lock internally in padata_alloc_possible
crypto: pcrypt - remove padata cpumask notifier
padata: make padata_do_parallel find alternate callback CPU
workqueue: require CPU hotplug read exclusion for apply_workqueue_attrs
workqueue: unconfine alloc/apply/free_workqueue_attrs()
padata: allocate workqueue internally
arm64: dts: imx8mq: Add CAAM node
random: Use wait_event_freezable() in add_hwgenerator_randomness()
crypto: ux500 - Fix COMPILE_TEST warnings
...
Sebastian reports that after commit ff296293b3 ("random: Support freezable
kthreads in add_hwgenerator_randomness()") we can call might_sleep() when the
task state is TASK_INTERRUPTIBLE (state=1). This leads to the following warning.
do not call blocking ops when !TASK_RUNNING; state=1 set at [<00000000349d1489>] prepare_to_wait_event+0x5a/0x180
WARNING: CPU: 0 PID: 828 at kernel/sched/core.c:6741 __might_sleep+0x6f/0x80
Modules linked in:
CPU: 0 PID: 828 Comm: hwrng Not tainted 5.3.0-rc7-next-20190903+ #46
RIP: 0010:__might_sleep+0x6f/0x80
Call Trace:
kthread_freezable_should_stop+0x1b/0x60
add_hwgenerator_randomness+0xdd/0x130
hwrng_fillfn+0xbf/0x120
kthread+0x10c/0x140
ret_from_fork+0x27/0x50
We shouldn't call kthread_freezable_should_stop() from deep within the
wait_event code because the task state is still set as
TASK_INTERRUPTIBLE instead of TASK_RUNNING and
kthread_freezable_should_stop() will try to call into the freezer with
the task in the wrong state. Use wait_event_freezable() instead so that
it calls schedule() in the right place and tries to enter the freezer
when the task state is TASK_RUNNING instead.
Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Tested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Keerthy <j-keerthy@ti.com>
Fixes: ff296293b3 ("random: Support freezable kthreads in add_hwgenerator_randomness()")
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Introducing a chosen node, rng-seed, which is an entropy that can be
passed to kernel called very early to increase initial device
randomness. Bootloader should provide this entropy and the value is
read from /chosen/rng-seed in DT.
Obtain of_fdt_crc32 for CRC check after early_init_dt_scan_nodes(),
since early_init_dt_scan_chosen() would modify fdt to erase rng-seed.
Add a new interface add_bootloader_randomness() for rng-seed use case.
Depends on whether the seed is trustworthy, rng seed would be passed to
add_hwgenerator_randomness(). Otherwise it would be passed to
add_device_randomness(). Decision is controlled by kernel config
RANDOM_TRUST_BOOTLOADER.
Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Theodore Ts'o <tytso@mit.edu> # drivers/char/random.c
Signed-off-by: Will Deacon <will@kernel.org>
The kthread calling this function is freezable after commit 03a3bb7ae6
("hwrng: core - Freeze khwrng thread during suspend") is applied.
Unfortunately, this function uses wait_event_interruptible() but doesn't
check for the kthread being woken up by the fake freezer signal. When a
user suspends the system, this kthread will wake up and if it fails the
entropy size check it will immediately go back to sleep and not go into
the freezer. Eventually, suspend will fail because the task never froze
and a warning message like this may appear:
PM: suspend entry (deep)
Filesystems sync: 0.000 seconds
Freezing user space processes ... (elapsed 0.001 seconds) done.
OOM killer disabled.
Freezing remaining freezable tasks ...
Freezing of tasks failed after 20.003 seconds (1 tasks refusing to freeze, wq_busy=0):
hwrng R running task 0 289 2 0x00000020
[<c08c64c4>] (__schedule) from [<c08c6a10>] (schedule+0x3c/0xc0)
[<c08c6a10>] (schedule) from [<c05dbd8c>] (add_hwgenerator_randomness+0xb0/0x100)
[<c05dbd8c>] (add_hwgenerator_randomness) from [<bf1803c8>] (hwrng_fillfn+0xc0/0x14c [rng_core])
[<bf1803c8>] (hwrng_fillfn [rng_core]) from [<c015abec>] (kthread+0x134/0x148)
[<c015abec>] (kthread) from [<c01010e8>] (ret_from_fork+0x14/0x2c)
Check for a freezer signal here and skip adding any randomness if the
task wakes up because it was frozen. This should make the kthread freeze
properly and suspend work again.
Fixes: 03a3bb7ae6 ("hwrng: core - Freeze khwrng thread during suspend")
Reported-by: Keerthy <j-keerthy@ti.com>
Tested-by: Keerthy <j-keerthy@ti.com>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Fixes: eb9d1bf079: "random: only read from /dev/random after its pool has received 128 bits"
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
The per-CPU variable batched_entropy_uXX is protected by get_cpu_var().
This is just a preempt_disable() which ensures that the variable is only
from the local CPU. It does not protect against users on the same CPU
from another context. It is possible that a preemptible context reads
slot 0 and then an interrupt occurs and the same value is read again.
The above scenario is confirmed by lockdep if we add a spinlock:
| ================================
| WARNING: inconsistent lock state
| 5.1.0-rc3+ #42 Not tainted
| --------------------------------
| inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
| ksoftirqd/9/56 [HC0[0]:SC1[1]:HE0:SE0] takes:
| (____ptrval____) (batched_entropy_u32.lock){+.?.}, at: get_random_u32+0x3e/0xe0
| {SOFTIRQ-ON-W} state was registered at:
| _raw_spin_lock+0x2a/0x40
| get_random_u32+0x3e/0xe0
| new_slab+0x15c/0x7b0
| ___slab_alloc+0x492/0x620
| __slab_alloc.isra.73+0x53/0xa0
| kmem_cache_alloc_node+0xaf/0x2a0
| copy_process.part.41+0x1e1/0x2370
| _do_fork+0xdb/0x6d0
| kernel_thread+0x20/0x30
| kthreadd+0x1ba/0x220
| ret_from_fork+0x3a/0x50
…
| other info that might help us debug this:
| Possible unsafe locking scenario:
|
| CPU0
| ----
| lock(batched_entropy_u32.lock);
| <Interrupt>
| lock(batched_entropy_u32.lock);
|
| *** DEADLOCK ***
|
| stack backtrace:
| Call Trace:
…
| kmem_cache_alloc_trace+0x20e/0x270
| ipmi_alloc_recv_msg+0x16/0x40
…
| __do_softirq+0xec/0x48d
| run_ksoftirqd+0x37/0x60
| smpboot_thread_fn+0x191/0x290
| kthread+0xfe/0x130
| ret_from_fork+0x3a/0x50
Add a spinlock_t to the batched_entropy data structure and acquire the
lock while accessing it. Acquire the lock with disabled interrupts
because this function may be used from interrupt context.
Remove the batched_entropy_reset_lock lock. Now that we have a lock for
the data scructure, we can access it from a remote CPU.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Explain what these functions are for and when they offer
an advantage over get_random_bytes().
(We still need documentation on rng_is_initialized(), the
random_ready_callback system, and early boot in general.)
Signed-off-by: George Spelvin <lkml@sdf.org>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
When the system boots with random.trust_cpu=1 it doesn't initialize the
per-NUMA CRNGs because it skips the rest of the CRNG startup code. This
means that the code from 1e7f583af6 ("random: make /dev/urandom scalable
for silly userspace programs") is not used when random.trust_cpu=1.
crash> dmesg | grep random:
[ 0.000000] random: get_random_bytes called from start_kernel+0x94/0x530 with crng_init=0
[ 0.314029] random: crng done (trusting CPU's manufacturer)
crash> print crng_node_pool
$6 = (struct crng_state **) 0x0
After adding the missing call to numa_crng_init() the per-NUMA CRNGs are
initialized again:
crash> dmesg | grep random:
[ 0.000000] random: get_random_bytes called from start_kernel+0x94/0x530 with crng_init=0
[ 0.314031] random: crng done (trusting CPU's manufacturer)
crash> print crng_node_pool
$1 = (struct crng_state **) 0xffff9a915f4014a0
The call to invalidate_batched_entropy() was also missing. This is
important for architectures like PPC and S390 which only have the
arch_get_random_seed_* functions.
Fixes: 39a8883a2b ("random: add a config option to trust the CPU's hwrng")
Signed-off-by: Jon DeVree <nuxi@vault24.org>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Right now rand_initialize() is run as an early_initcall(), but it only
depends on timekeeping_init() (for mixing ktime_get_real() into the
pools). However, the call to boot_init_stack_canary() for stack canary
initialization runs earlier, which triggers a warning at boot:
random: get_random_bytes called from start_kernel+0x357/0x548 with crng_init=0
Instead, this moves rand_initialize() to after timekeeping_init(), and moves
canary initialization here as well.
Note that this warning may still remain for machines that do not have
UEFI RNG support (which initializes the RNG pools during setup_arch()),
or for x86 machines without RDRAND (or booting without "random.trust=on"
or CONFIG_RANDOM_TRUST_CPU=y).
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Immediately after boot, we allow reads from /dev/random before its
entropy pool has been fully initialized. Fix this so that we don't
allow this until the blocking pool has received 128 bits.
We do this by repurposing the initialized flag in the entropy pool
struct, and use the initialized flag in the blocking pool to indicate
whether it is safe to pull from the blocking pool.
To do this, we needed to rework when we decide to push entropy from the
input pool to the blocking pool, since the initialized flag for the
input pool was used for this purpose. To simplify things, we no
longer use the initialized flag for that purpose, nor do we use the
entropy_total field any more.
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Since the definition of struct crng_state is private to random.c, and
primary_crng is neither declared or used elsewhere, there's no reason
for that symbol to have external linkage.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This field is never used, might as well remove it.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Never modified, might as well be put in .rodata.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
In preparation for adding XChaCha12 support, rename/refactor
chacha20-generic to support different numbers of rounds. The
justification for needing XChaCha12 support is explained in more detail
in the patch "crypto: chacha - add XChaCha12 support".
The only difference between ChaCha{8,12,20} are the number of rounds
itself; all other parts of the algorithm are the same. Therefore,
remove the "20" from all definitions, structures, functions, files, etc.
that will be shared by all ChaCha versions.
Also make ->setkey() store the round count in the chacha_ctx (previously
chacha20_ctx). The generic code then passes the round count through to
chacha_block(). There will be a ->setkey() function for each explicitly
allowed round count; the encrypt/decrypt functions will be the same. I
decided not to do it the opposite way (same ->setkey() function for all
round counts, with different encrypt/decrypt functions) because that
would have required more boilerplate code in architecture-specific
implementations of ChaCha and XChaCha.
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Martin Willi <martin@strongswan.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
In commit 9f480faec5 ("crypto: chacha20 - Fix keystream alignment for
chacha20_block()"), I had missed that chacha20_block() can be called
directly on the buffer passed to get_random_bytes(), which can have any
alignment. So, while my commit didn't break anything, it didn't fully
solve the alignment problems.
Revert my solution and just update chacha20_block() to use
put_unaligned_le32(), so the output buffer need not be aligned.
This is simpler, and on many CPUs it's the same speed.
But, I kept the 'tmp' buffers in extract_crng_user() and
_get_random_bytes() 4-byte aligned, since that alignment is actually
needed for _crng_backtrack_protect() too.
Reported-by: Stephan Müller <smueller@chronox.de>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Instead of forcing a distro or other system builder to choose
at build time whether the CPU is trusted for CRNG seeding via
CONFIG_RANDOM_TRUST_CPU, provide a boot-time parameter for end users to
control the choice. The CONFIG will set the default state instead.
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
It is very useful to be able to know whether or not get_random_bytes_wait
/ wait_for_random_bytes is going to block or not, or whether plain
get_random_bytes is going to return good randomness or bad randomness.
The particular use case is for mitigating certain attacks in WireGuard.
A handshake packet arrives and is queued up. Elsewhere a worker thread
takes items from the queue and processes them. In replying to these
items, it needs to use some random data, and it has to be good random
data. If we simply block until we can have good randomness, then it's
possible for an attacker to fill the queue up with packets waiting to be
processed. Upon realizing the queue is full, WireGuard will detect that
it's under a denial of service attack, and behave accordingly. A better
approach is just to drop incoming handshake packets if the crng is not
yet initialized.
This patch, therefore, makes that information directly accessible.
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
No need to keep preemption disabled across the whole function.
mix_pool_bytes() uses a spin_lock() to protect the pool and there are
other places like write_pool() whhich invoke mix_pool_bytes() without
disabling preemption.
credit_entropy_bits() is invoked from other places like
add_hwgenerator_randomness() without disabling preemption.
Before commit 95b709b6be ("random: drop trickle mode") the function
used __this_cpu_inc_return() which would require disabled preemption.
The preempt_disable() section was added in commit 43d5d3018c37 ("[PATCH]
random driver preempt robustness", history tree). It was claimed that
the code relied on "vt_ioctl() being called under BKL".
Cc: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
[bigeasy: enhance the commit message]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This gives the user building their own kernel (or a Linux
distribution) the option of deciding whether or not to trust the CPU's
hardware random number generator (e.g., RDRAND for x86 CPU's) as being
correctly implemented and not having a back door introduced (perhaps
courtesy of a Nation State's law enforcement or intelligence
agencies).
This will prevent getrandom(2) from blocking, if there is a
willingness to trust the CPU manufacturer.
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Currently the function get_random_bytes_arch() has return value 'void'.
If the hw RNG fails we currently fall back to using get_random_bytes().
This defeats the purpose of requesting random material from the hw RNG
in the first place.
There are currently no intree users of get_random_bytes_arch().
Only get random bytes from the hw RNG, make function return the number
of bytes retrieved from the hw RNG.
Acked-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Tobin C. Harding <me@tobin.cc>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
There are a couple of whitespace issues around the function
get_random_bytes_arch(). In preparation for patching this function
let's clean them up.
Acked-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Tobin C. Harding <me@tobin.cc>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Fedora has integrated the jitter entropy daemon to work around slow
boot problems, especially on VM's that don't support virtio-rng:
https://bugzilla.redhat.com/show_bug.cgi?id=1572944
It's understandable why they did this, but the Jitter entropy daemon
works fundamentally on the principle: "the CPU microarchitecture is
**so** complicated and we can't figure it out, so it *must* be
random". Yes, it uses statistical tests to "prove" it is secure, but
AES_ENCRYPT(NSA_KEY, COUNTER++) will also pass statistical tests with
flying colors.
So if RDRAND is available, mix it into entropy submitted from
userspace. It can't hurt, and if you believe the NSA has backdoored
RDRAND, then they probably have enough details about the Intel
microarchitecture that they can reverse engineer how the Jitter
entropy daemon affects the microarchitecture, and attack its output
stream. And if RDRAND is in fact an honest DRNG, it will immeasurably
improve on what the Jitter entropy daemon might produce.
This also provides some protection against someone who is able to read
or set the entropy seed file.
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org
Cc: Arnd Bergmann <arnd@arndb.de>
The poll() changes were not well thought out, and completely
unexplained. They also caused a huge performance regression, because
"->poll()" was no longer a trivial file operation that just called down
to the underlying file operations, but instead did at least two indirect
calls.
Indirect calls are sadly slow now with the Spectre mitigation, but the
performance problem could at least be largely mitigated by changing the
"->get_poll_head()" operation to just have a per-file-descriptor pointer
to the poll head instead. That gets rid of one of the new indirections.
But that doesn't fix the new complexity that is completely unwarranted
for the regular case. The (undocumented) reason for the poll() changes
was some alleged AIO poll race fixing, but we don't make the common case
slower and more complex for some uncommon special case, so this all
really needs way more explanations and most likely a fundamental
redesign.
[ This revert is a revert of about 30 different commits, not reverted
individually because that would just be unnecessarily messy - Linus ]
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The big change is that random_read_wait and random_write_wait are merged
into a single waitqueue that uses keyed wakeups. Because wait_event_*
doesn't know about that this will lead to occassional spurious wakeups
in _random_read and add_hwgenerator_randomness, but wait_event_* is
designed to handle these and were are not in a a hot path there.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
We can do a sleeping allocation from an irq context when CONFIG_NUMA
is enabled. Fix this by initializing the NUMA crng instances in a
workqueue.
Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reported-by: syzbot+9de458f6a5e713ee8c1a@syzkaller.appspotmail.com
Fixes: 8ef35c866f ("random: set up the NUMA crng instances...")
Cc: stable@vger.kernel.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Until the primary_crng is fully initialized, don't initialize the NUMA
crng nodes. Otherwise users of /dev/urandom on NUMA systems before
the CRNG is fully initialized can get very bad quality randomness. Of
course everyone should move to getrandom(2) where this won't be an
issue, but there's a lot of legacy code out there. This related to
CVE-2018-1108.
Reported-by: Jann Horn <jannh@google.com>
Fixes: 1e7f583af6 ("random: make /dev/urandom scalable for silly...")
Cc: stable@kernel.org # 4.8+
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
add_device_randomness() use of crng_fast_load() was highly
problematic. Some callers of add_device_randomness() can pass in a
large amount of static information. This would immediately promote
the crng_init state from 0 to 1, without really doing much to
initialize the primary_crng's internal state with something even
vaguely unpredictable.
Since we don't have the speed constraints of add_interrupt_randomness(),
we can do a better job mixing in the what unpredictability a device
driver or architecture maintainer might see fit to give us, and do it
in a way which does not bump the crng_init_cnt variable.
Also, since add_device_randomness() doesn't bump any entropy
accounting in crng_init state 0, mix the device randomness into the
input_pool entropy pool as well. This is related to CVE-2018-1108.
Reported-by: Jann Horn <jannh@google.com>
Fixes: ee7998c50c ("random: do not ignore early device randomness")
Cc: stable@kernel.org # 4.13+
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
