5.7.14-rc1 review

This is the start of the stable review cycle for the 5.7.14 release. There are 6 patches in this series, all will be posted as a response to this one. If anyone has any issues with these being applied, please let me know.

Responses should be made by Fri, 07 Aug 2020 15:34:53 +0000. Anything received after that time might be too late.

The whole patch series can be found in one patch at:

	https://www.kernel.org/pub/linux/kernel/v5.x/stable-review/patch-5.7.14-rc1.gz

or in the git tree and branch at:
git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git linux-5.7.y
and the diffstat can be found below.

thanks,

greg k-h

-------------
Pseudo-Shortlog of commits:

Greg Kroah-Hartman <[email protected]>

    Linux 5.7.14-rc1

Marc Zyngier <[email protected]>
arm64: Workaround circular dependency in pointer_auth.h

Linus Torvalds <[email protected]>
random32: move the pseudo-random 32-bit definitions to prandom.h

Linus Torvalds <[email protected]>
random32: remove net_rand_state from the latent entropy gcc plugin

Willy Tarreau <[email protected]>
random: fix circular include dependency on arm64 after addition of percpu.h

Grygorii Strashko <[email protected]>
ARM: percpu.h: fix build error

Willy Tarreau <[email protected]>
random32: update the net random state on interrupt and activity

-------------

Diffstat:

 Makefile                              |  4 +-
 arch/arm/include/asm/percpu.h         |  2 +
 arch/arm64/include/asm/pointer_auth.h |  8 +++-
 drivers/char/random.c                 |  1 +
 include/linux/prandom.h               | 78 +++++++++++++++++++++++++++++++++++
 include/linux/random.h                | 63 ++--------------------------
 kernel/time/timer.c                   |  8 ++++
 lib/random32.c                        |  2 +-
 8 files changed, 103 insertions(+), 63 deletions(-)

From: Willy Tarreau <[email protected]>

commit f227e3ec3b5cad859ad15666874405e8c1bbc1d4 upstream.

This modifies the first 32 bits out of the 128 bits of a random CPU's net_rand_state on interrupt or CPU activity to complicate remote observations that could lead to guessing the network RNG's internal state.

Note that depending on some network devices' interrupt rate moderation or binding, this re-seeding might happen on every packet or even almost never.

In addition, with NOHZ some CPUs might not even get timer interrupts, leaving their local state rarely updated, while they are running networked processes making use of the random state. For this reason, we also perform this update in update_process_times() in order to at least update the state when there is user or system activity, since it's the only case we care about.

---
 drivers/char/random.c  |    1 +
 include/linux/random.h |    3 +++
 kernel/time/timer.c    |    8 ++++++++
 lib/random32.c         |    2 +-
 4 files changed, 13 insertions(+), 1 deletion(-)

@@ -1277,6 +1277,7 @@ void add_interrupt_randomness(int irq, i
 
 	fast_mix(fast_pool);
 	add_interrupt_bench(cycles);
+	this_cpu_add(net_rand_state.s1, fast_pool->pool[cycles & 3]);
 
 	if (unlikely(crng_init == 0)) {
 		if ((fast_pool->count >= 64) &&

@@ -11,6 +11,7 @@
 #include <linux/kernel.h>
 #include <linux/list.h>
 #include <linux/once.h>
+#include <linux/percpu.h>
 
 #include <uapi/linux/random.h>
 

@@ -119,6 +120,8 @@ struct rnd_state {
 	__u32 s1, s2, s3, s4;
 };
 
+DECLARE_PER_CPU(struct rnd_state, net_rand_state) __latent_entropy;
+
 u32 prandom_u32_state(struct rnd_state *state);
 void prandom_bytes_state(struct rnd_state *state, void *buf, size_t nbytes);
 void prandom_seed_full_state(struct rnd_state __percpu *pcpu_state);

@@ -43,6 +43,7 @@
 #include <linux/sched/debug.h>
 #include <linux/slab.h>
 #include <linux/compat.h>
+#include <linux/random.h>
 
 #include <linux/uaccess.h>
 #include <asm/unistd.h>

@@ -1743,6 +1744,13 @@ void update_process_times(int user_tick)
 	scheduler_tick();
 	if (IS_ENABLED(CONFIG_POSIX_TIMERS))
 		run_posix_cpu_timers();
+
+	/* The current CPU might make use of net randoms without receiving IRQs
+	 * to renew them often enough. Let's update the net_rand_state from a
+	 * non-constant value that's not affine to the number of calls to make
+	 * sure it's updated when there's some activity (we don't care in idle).
+	 */
+	this_cpu_add(net_rand_state.s1, rol32(jiffies, 24) + user_tick);
 }
 
 /**

@@ -48,7 +48,7 @@ static inline void prandom_state_selftes
 }
 #endif
 
-static DEFINE_PER_CPU(struct rnd_state, net_rand_state) __latent_entropy;
+DEFINE_PER_CPU(struct rnd_state, net_rand_state) __latent_entropy;
 
 /**
  *	prandom_u32_state - seeded pseudo-random number generator.

From: Grygorii Strashko <[email protected]>

commit aa54ea903abb02303bf55855fb51e3fcee135d70 upstream.

Fix build error for the case:
defined(CONFIG_SMP) && !defined(CONFIG_CPU_V6)

config: keystone_defconfig

CC arch/arm/kernel/signal.o
In file included from ../include/linux/random.h:14,

                    from ../arch/arm/kernel/signal.c:8:
  ../arch/arm/include/asm/percpu.h: In function ‘__my_cpu_offset’:
  ../arch/arm/include/asm/percpu.h:29:34: error: ‘current_stack_pointer’ undeclared (first use in this function); did you mean ‘user_stack_pointer’?
      : "Q" (*(const unsigned long *)current_stack_pointer));
                                     ^~~~~~~~~~~~~~~~~~~~~
                                     user_stack_pointer

---
 arch/arm/include/asm/percpu.h |    2 ++
 1 file changed, 2 insertions(+)

@@ -5,6 +5,8 @@
 #ifndef _ASM_ARM_PERCPU_H_
 #define _ASM_ARM_PERCPU_H_
 
+#include <asm/thread_info.h>
+
 /*
  * Same as asm-generic/percpu.h, except that we store the per cpu offset
  * in the TPIDRPRW. TPIDRPRW only exists on V6K and V7

From: Willy Tarreau <[email protected]>

commit 1c9df907da83812e4f33b59d3d142c864d9da57f upstream.

Daniel Díaz and Kees Cook independently reported that commit f227e3ec3b5c ("random32: update the net random state on interrupt and activity") broke arm64 due to a circular dependency on include files since the addition of percpu.h in random.h.

The correct fix would definitely be to move all the prandom32 stuff out of random.h but for backporting, a smaller solution is preferred.

This one replaces linux/percpu.h with asm/percpu.h, and this fixes the problem on x86_64, arm64, arm, and mips. Note that moving percpu.h around didn't change anything and that removing it entirely broke differently. When backporting, such options might still be considered if this patch fails to help.

[ It turns out that an alternate fix seems to be to just remove the
troublesome <asm/pointer_auth.h> remove from the arm64 <asm/smp.h> that causes the circular dependency.

But we might as well do the whole belt-and-suspenders thing, and minimize inclusion in <linux/random.h> too. Either will fix the
problem, and both are good changes. - Linus ]

---
 include/linux/random.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -11,7 +11,7 @@
 #include <linux/kernel.h>
 #include <linux/list.h>
 #include <linux/once.h>
-#include <linux/percpu.h>
+#include <asm/percpu.h>
 
 #include <uapi/linux/random.h>
 

[ sorry if it is not interesting ! ]

While building with old gcc-7.3.0 the build breaks for arm64 whereas build PASS on gcc-8, gcc-9 and gcc-10.

with gcc 7.3.0 build breaks log,

In file included from arch/arm64/include/asm/archrandom.h:9:0,

                 from arch/arm64/kernel/kaslr.c:14:

include/linux/random.h: In function 'arch_get_random_seed_long_early':
include/linux/random.h:149:9: error: implicit declaration of function 'arch_get_random_seed_long'; did you mean 'arch_get_random_seed_long_early'? [-Werror=implicit-function-declaration]

  return arch_get_random_seed_long(v);
         ^~~~~~~~~~~~~~~~~~~~~~~~~
         arch_get_random_seed_long_early

include/linux/random.h: In function 'arch_get_random_long_early':
include/linux/random.h:157:9: error: implicit declaration of function 'arch_get_random_long'; did you mean 'get_random_long'? [-Werror=implicit-function-declaration]

  return arch_get_random_long(v);
         ^~~~~~~~~~~~~~~~~~~~
         get_random_long

In file included from arch/arm64/kernel/kaslr.c:14:0:
arch/arm64/include/asm/archrandom.h: At top level:
arch/arm64/include/asm/archrandom.h:30:33: error: conflicting types for 'arch_get_random_long'
static inline bool __must_check arch_get_random_long(unsigned long *v)

                                 ^~~~~~~~~~~~~~~~~~~~
In file included from arch/arm64/include/asm/archrandom.h:9:0,
                 from arch/arm64/kernel/kaslr.c:14:
include/linux/random.h:157:9: note: previous implicit declaration of
'arch_get_random_long' was here
  return arch_get_random_long(v);
         ^~~~~~~~~~~~~~~~~~~~

In file included from arch/arm64/kernel/kaslr.c:14:0:
arch/arm64/include/asm/archrandom.h:40:33: error: conflicting types for 'arch_get_random_seed_long'
static inline bool __must_check arch_get_random_seed_long(unsigned long *v)

                                 ^~~~~~~~~~~~~~~~~~~~~~~~~
In file included from arch/arm64/include/asm/archrandom.h:9:0,
                 from arch/arm64/kernel/kaslr.c:14:
include/linux/random.h:149:9: note: previous implicit declaration of
'arch_get_random_seed_long' was here
  return arch_get_random_seed_long(v);
         ^~~~~~~~~~~~~~~~~~~~~~~~~

In file included from arch/arm64/kernel/kaslr.c:14:0:
arch/arm64/include/asm/archrandom.h:72:1: error: redefinition of 'arch_get_random_seed_long_early'
arch_get_random_seed_long_early(unsigned long *v) ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from arch/arm64/include/asm/archrandom.h:9:0,

                 from arch/arm64/kernel/kaslr.c:14:

include/linux/random.h:146:27: note: previous definition of 'arch_get_random_seed_long_early' was here
static inline bool __init arch_get_random_seed_long_early(unsigned long *v)

Linaro LKFT
https://lkft.linaro.org

It's a bit interesting only because it is so odd.

Can you double-check that your gcc-7.3 setup is actually building the same tree?

Yeah, I know that's a slightly strange thing to ask, but your build log really looks very odd. There should be nothing in that error that is in any way compiler version specific.

Sure, we may have some header that checks the compiler version and does something different based on that, and I guess that could be going on. Except I don't even find anything remotely like that anywhere. I do find some compiler version tests, but most ofd them would trigger for all those compiler versions

Or is there perhaps some other configuration difference?

Linus

I see the same problem. I built images manually, using the same source tree, so I am quite sure it is the same tree (at least in my case).

Same confusion here. I'll be stuck in a meeting for the next hour; unless someone else figures out what is going on I'll get back to it afterwards.

Guenter

Same with older versions of gcc. I don't see the problem with the mainline kernel.

I think this is caused by more recursive includes. arch/arm64/include/asm/archrandom.h includes include/linux/random.h which includes arch/arm64/include/asm/archrandom.h to get the definition of arch_get_random_seed_long_early (which it won't get because of the recursion).

What I don't really understand is how this works with new versions of gcc.

Guenter

https://www.youtube.com/watch?v=-b5aW08ivHU

Is that the only place it triggers?

Because the trivial fix would be something like the appended, which is the right thing to do anyway.

Linus

index 07c4c8cc4a67..9ded4237e1c1 100644
@@ -11,8 +11,8 @@
 #include <linux/sched.h>
 #include <linux/types.h>
 #include <linux/pgtable.h>
+#include <linux/random.h>
 
-#include <asm/archrandom.h>
 #include <asm/cacheflush.h>
 #include <asm/fixmap.h>
 #include <asm/kernel-pgtable.h>

Correct.

gcc-7.x and older don't support CONFIG_ARM64_PTR_AUTH. Result is that ./arch/arm64/include/asm/pointer_auth.h doesn't include <linux/random.h> for those compiler versions, which results in the problem.

In the mainline kernel, ./arch/arm64/include/asm/pointer_auth.h always includes <linux/random.h>, so the problem isn't seen (or, rather, it is hidden) there.

The problem is caused (exposed) by Marc's commit ("arm64: Workaround circular dependency in pointer_auth.h"), which makes the include of linux/random.h conditional.

Guenter

I'll take that as an Ack, and also remove the crazy reverse include from archrandom.h that most definitely shouldn't be there.

It's now commit 585524081ecd ("random: random.h should include archrandom.h, not the other way around") in my tree, because a grep for "archrandom.h" shows that now the only place it exists is <linux/random.h> and a few files that cannot possibly affect arm64 (because they are on x86 and powerpc, neither of which has that insane reverse include).

Linus

Thanks, I've queued this up for 5.7.y now. Doesn't look relevant for older kernels, but I haven't gotten reports of them not building just yet :)

thanks,

greg k-h

Thanks, appreciated.

I tried to build arm64 on current mainline, after reverting the dts patches which cause the build failures there. Builds fine with both gcc 7.4.0 and 9.3.0. 5.7.14-rc2 builds as well with both old and new compilers. So hopefully we are fine.

Guenter

Hello!

Yes

From: Linus Torvalds <[email protected]>

commit 83bdc7275e6206f560d247be856bceba3e1ed8f2 upstream.

It turns out that the plugin right now ends up being really unhappy about the change from 'static' to 'extern' storage that happened in commit f227e3ec3b5c ("random32: update the net random state on interrupt and activity").

This is probably a trivial fix for the latent_entropy plugin, but for now, just remove net_rand_state from the list of things the plugin worries about.

---
 include/linux/random.h |    2 +-
 lib/random32.c         |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

@@ -120,7 +120,7 @@ struct rnd_state {
 	__u32 s1, s2, s3, s4;
 };
 
-DECLARE_PER_CPU(struct rnd_state, net_rand_state) __latent_entropy;
+DECLARE_PER_CPU(struct rnd_state, net_rand_state);
 
 u32 prandom_u32_state(struct rnd_state *state);
 void prandom_bytes_state(struct rnd_state *state, void *buf, size_t nbytes);

@@ -48,7 +48,7 @@ static inline void prandom_state_selftes
 }
 #endif
 
-DEFINE_PER_CPU(struct rnd_state, net_rand_state) __latent_entropy;
+DEFINE_PER_CPU(struct rnd_state, net_rand_state);
 
 /**
  *	prandom_u32_state - seeded pseudo-random number generator.

All tests passing for Tegra ...

Test results for stable-v5.7:

    11 builds:	11 pass, 0 fail
    26 boots:	26 pass, 0 fail
    56 tests:	56 pass, 0 fail

Linux version: 5.7.14-rc1-g3bd8d605f0dc
Boards tested: tegra124-jetson-tk1, tegra186-p2771-0000,

                tegra194-p2972-0000, tegra20-ventana,
                tegra210-p2371-2180, tegra210-p3450-0000,
                tegra30-cardhu-a04

Jon

From: Linus Torvalds <[email protected]>

commit c0842fbc1b18c7a044e6ff3e8fa78bfa822c7d1a upstream.

The addition of percpu.h to the list of includes in random.h revealed some circular dependencies on arm64 and possibly other platforms. This include was added solely for the pseudo-random definitions, which have nothing to do with the rest of the definitions in this file but are still there for legacy reasons.

This patch moves the pseudo-random parts to linux/prandom.h and the percpu.h include with it, which is now guarded by _LINUX_PRANDOM_H and protected against recursive inclusion.

A further cleanup step would be to remove this from <linux/random.h> entirely, and make people who use the prandom infrastructure include just the new header file. That's a bit of a churn patch, but grepping for "prandom_" and "next_pseudo_random32" "struct rnd_state" should catch most users.

But it turns out that that nice cleanup step is fairly painful, because a _lot_ of code currently seems to depend on the implicit include of <linux/random.h>, which can currently come in a lot of ways, including such fairly core headfers as <linux/net.h>.

So the "nice cleanup" part may or may never happen.

---
 include/linux/prandom.h |   78 ++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/random.h  |   66 ++--------------------------------------
 2 files changed, 82 insertions(+), 62 deletions(-)

@@ -0,0 +1,78 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * include/linux/prandom.h
+ *
+ * Include file for the fast pseudo-random 32-bit
+ * generation.
+ */
+#ifndef _LINUX_PRANDOM_H
+#define _LINUX_PRANDOM_H
+
+#include <linux/types.h>
+#include <linux/percpu.h>
+
+u32 prandom_u32(void);
+void prandom_bytes(void *buf, size_t nbytes);
+void prandom_seed(u32 seed);
+void prandom_reseed_late(void);
+
+struct rnd_state {
+	__u32 s1, s2, s3, s4;
+};
+
+DECLARE_PER_CPU(struct rnd_state, net_rand_state);
+
+u32 prandom_u32_state(struct rnd_state *state);
+void prandom_bytes_state(struct rnd_state *state, void *buf, size_t nbytes);
+void prandom_seed_full_state(struct rnd_state __percpu *pcpu_state);
+
+#define prandom_init_once(pcpu_state)			\
+	DO_ONCE(prandom_seed_full_state, (pcpu_state))
+
+/**
+ * prandom_u32_max - returns a pseudo-random number in interval [0, ep_ro)
+ * @ep_ro: right open interval endpoint
+ *
+ * Returns a pseudo-random number that is in interval [0, ep_ro). Note
+ * that the result depends on PRNG being well distributed in [0, ~0U]
+ * u32 space. Here we use maximally equidistributed combined Tausworthe
+ * generator, that is, prandom_u32(). This is useful when requesting a
+ * random index of an array containing ep_ro elements, for example.
+ *
+ * Returns: pseudo-random number in interval [0, ep_ro)
+ */
+static inline u32 prandom_u32_max(u32 ep_ro)
+{
+	return (u32)(((u64) prandom_u32() * ep_ro) >> 32);
+}
+
+/*
+ * Handle minimum values for seeds
+ */
+static inline u32 __seed(u32 x, u32 m)
+{
+	return (x < m) ? x + m : x;
+}
+
+/**
+ * prandom_seed_state - set seed for prandom_u32_state().
+ * @state: pointer to state structure to receive the seed.
+ * @seed: arbitrary 64-bit value to use as a seed.
+ */
+static inline void prandom_seed_state(struct rnd_state *state, u64 seed)
+{
+	u32 i = (seed >> 32) ^ (seed << 10) ^ seed;
+
+	state->s1 = __seed(i,   2U);
+	state->s2 = __seed(i,   8U);
+	state->s3 = __seed(i,  16U);
+	state->s4 = __seed(i, 128U);
+}
+
+/* Pseudo random number generator from numerical recipes. */
+static inline u32 next_pseudo_random32(u32 seed)
+{
+	return seed * 1664525 + 1013904223;
+}
+
+#endif

From: Marc Zyngier <[email protected]>

With the backport of f227e3ec3b5c ("random32: update the net random state on interrupt and activity") and its associated fixes, the arm64 build explodes early:

In file included from ../include/linux/smp.h:67,

                  from ../include/linux/percpu.h:7,
                  from ../include/linux/prandom.h:12,
                  from ../include/linux/random.h:118,
                  from ../arch/arm64/include/asm/pointer_auth.h:6,
                  from ../arch/arm64/include/asm/processor.h:39,
                  from ../include/linux/mutex.h:19,
                  from ../include/linux/kernfs.h:12,
                  from ../include/linux/sysfs.h:16,
                  from ../include/linux/kobject.h:20,
                  from ../include/linux/of.h:17,
                  from ../include/linux/irqdomain.h:35,
                  from ../include/linux/acpi.h:13,
                  from ../include/acpi/apei.h:9,
                  from ../include/acpi/ghes.h:5,
                  from ../include/linux/arm_sdei.h:8,
                  from ../arch/arm64/kernel/asm-offsets.c:10:

../arch/arm64/include/asm/smp.h:100:29: error: field ‘ptrauth_key’ has incomplete type

This is due to struct ptrauth_keys_kernel not being defined before we transitively include asm/smp.h from linux/random.h.

Paper over it by moving the inclusion of linux/random.h *after* the type has been defined.

---
 arch/arm64/include/asm/pointer_auth.h |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

@@ -3,7 +3,6 @@
 #define __ASM_POINTER_AUTH_H
 
 #include <linux/bitops.h>
-#include <linux/random.h>
 
 #include <asm/cpufeature.h>
 #include <asm/memory.h>

@@ -34,6 +33,13 @@ struct ptrauth_keys_kernel {
 	struct ptrauth_key apia;
 };
 
+/*
+ * Only include random.h once ptrauth_keys_* structures are defined
+ * to avoid yet another circular include hell (random.h * ends up
+ * including asm/smp.h, which requires ptrauth_keys_kernel).
+ */
+#include <linux/random.h>
+
 static inline void ptrauth_keys_init_user(struct ptrauth_keys_user *keys)
 {
 	if (system_supports_address_auth()) {