linux-stable.git/drivers/char/random.c, branch v4.9.166

random: mix rdrand with entropy sent in from userspace

2018-08-03T05:55:26+00:00

commit 81e69df38e2911b642ec121dec319fad2a4782f3 upstream.

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 
Cc: stable@vger.kernel.org
Cc: Arnd Bergmann 
Signed-off-by: Greg Kroah-Hartman

random: rate limit unseeded randomness warnings

2018-05-01T22:13:04+00:00

commit 4e00b339e264802851aff8e73cde7d24b57b18ce upstream.

On systems without sufficient boot randomness, no point spamming dmesg.

Signed-off-by: Theodore Ts'o 
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman

random: fix possible sleeping allocation from irq context

2018-05-01T22:13:03+00:00

commit 6c1e851c4edc13a43adb3ea4044e3fc8f43ccf7d upstream.

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 
Reported-by: syzbot+9de458f6a5e713ee8c1a@syzkaller.appspotmail.com
Fixes: 8ef35c866f8862df ("random: set up the NUMA crng instances...")
Cc: stable@vger.kernel.org
Signed-off-by: Theodore Ts'o 
Signed-off-by: Greg Kroah-Hartman

random: set up the NUMA crng instances after the CRNG is fully initialized

2018-05-01T22:13:03+00:00

commit 8ef35c866f8862df074a49a93b0309725812dea8 upstream.

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 
Fixes: 1e7f583af67b ("random: make /dev/urandom scalable for silly...")
Cc: stable@kernel.org # 4.8+
Signed-off-by: Theodore Ts'o 
Signed-off-by: Greg Kroah-Hartman

random: add new ioctl RNDRESEEDCRNG

2018-04-24T07:34:16+00:00

commit d848e5f8e1ebdb227d045db55fe4f825e82965fa upstream.

Add a new ioctl which forces the the crng to be reseeded.

Signed-off-by: Theodore Ts'o 
Cc: stable@kernel.org
Signed-off-by: Greg Kroah-Hartman

random: crng_reseed() should lock the crng instance that it is modifying

2018-04-24T07:34:16+00:00

commit 0bb29a849a6433b72e249eea7695477b02056e94 upstream.

Reported-by: Jann Horn 
Fixes: 1e7f583af67b ("random: make /dev/urandom scalable for silly...")
Cc: stable@kernel.org # 4.8+
Signed-off-by: Theodore Ts'o 
Reviewed-by: Jann Horn 
Signed-off-by: Greg Kroah-Hartman

random: fix crng_ready() test

2018-04-24T07:34:16+00:00

commit 43838a23a05fbd13e47d750d3dfd77001536dd33 upstream.

The crng_init variable has three states:

0: The CRNG is not initialized at all
1: The CRNG has a small amount of entropy, hopefully good enough for
   early-boot, non-cryptographical use cases
2: The CRNG is fully initialized and we are sure it is safe for
   cryptographic use cases.

The crng_ready() function should only return true once we are in the
last state.  This addresses CVE-2018-1108.

Reported-by: Jann Horn 
Fixes: e192be9d9a30 ("random: replace non-blocking pool...")
Cc: stable@kernel.org # 4.8+
Signed-off-by: Theodore Ts'o 
Reviewed-by: Jann Horn 
Signed-off-by: Greg Kroah-Hartman

random: use a tighter cap in credit_entropy_bits_safe()

2018-04-24T07:34:12+00:00

commit 9f886f4d1d292442b2f22a0a33321eae821bde40 upstream.

This fixes a harmless UBSAN where root could potentially end up
causing an overflow while bumping the entropy_total field (which is
ignored once the entropy pool has been initialized, and this generally
is completed during the boot sequence).

This is marginal for the stable kernel series, but it's a really
trivial patch, and it fixes UBSAN warning that might cause security
folks to get overly excited for no reason.

Signed-off-by: Theodore Ts'o 
Reported-by: Chen Feng 
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman

random: use lockless method of accessing and updating f->reg_idx

2018-04-13T17:48:32+00:00

commit 92e75428ffc90e2a0321062379f883f3671cfebe upstream.

Linus pointed out that there is a much more efficient way of avoiding
the problem that we were trying to address in commit 9dfa7bba35ac0:
"fix race in drivers/char/random.c:get_reg()".

Signed-off-by: Theodore Ts'o 
Cc: Michael Schmitz 
Signed-off-by: Greg Kroah-Hartman

fix race in drivers/char/random.c:get_reg()

2018-04-13T17:48:06+00:00

[ Upstream commit 9dfa7bba35ac08a63565d58c454dccb7e1bb0a08 ]

get_reg() can be reentered on architectures with prioritized interrupts
(m68k in this case), causing f->reg_index to be incremented after the
range check. Out of bounds memory access past the pt_regs struct results.
This will go mostly undetected unless access is beyond end of memory.

Prevent the race by disabling interrupts in get_reg().

Tested on m68k (Atari Falcon, and ARAnyM emulator).

Kudos to Geert Uytterhoeven for helping to trace this race.

Signed-off-by: Michael Schmitz 
Signed-off-by: Theodore Ts'o 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman