From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
stable@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
Arnd Bergmann <arnd@arndb.de>,
"Russell King (Oracle)" <rmk+kernel@armlinux.org.uk>,
"Jason A. Donenfeld" <Jason@zx2c4.com>
Subject: [PATCH 5.18 14/47] arm: use fallback for random_get_entropy() instead of zero
Date: Fri, 27 May 2022 10:49:54 +0200 [thread overview]
Message-ID: <20220527084803.662215479@linuxfoundation.org> (raw)
In-Reply-To: <20220527084801.223648383@linuxfoundation.org>
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
commit ff8a8f59c99f6a7c656387addc4d9f2247d75077 upstream.
In the event that random_get_entropy() can't access a cycle counter or
similar, falling back to returning 0 is really not the best we can do.
Instead, at least calling random_get_entropy_fallback() would be
preferable, because that always needs to return _something_, even
falling back to jiffies eventually. It's not as though
random_get_entropy_fallback() is super high precision or guaranteed to
be entropic, but basically anything that's not zero all the time is
better than returning zero all the time.
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/arm/include/asm/timex.h | 1 +
1 file changed, 1 insertion(+)
--- a/arch/arm/include/asm/timex.h
+++ b/arch/arm/include/asm/timex.h
@@ -11,5 +11,6 @@
typedef unsigned long cycles_t;
#define get_cycles() ({ cycles_t c; read_current_timer(&c) ? 0 : c; })
+#define random_get_entropy() (((unsigned long)get_cycles()) ?: random_get_entropy_fallback())
#endif
next prev parent reply other threads:[~2022-05-27 8:52 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-27 8:49 [PATCH 5.18 00/47] 5.18.1-rc1 review Greg Kroah-Hartman
2022-05-27 8:49 ` [PATCH 5.18 01/47] lockdown: also lock down previous kgdb use Greg Kroah-Hartman
2022-05-27 8:49 ` [PATCH 5.18 02/47] HID: amd_sfh: Add support for sensor discovery Greg Kroah-Hartman
2022-05-27 8:49 ` [PATCH 5.18 03/47] random: fix sysctl documentation nits Greg Kroah-Hartman
2022-05-27 8:49 ` [PATCH 5.18 04/47] init: call time_init() before rand_initialize() Greg Kroah-Hartman
2022-05-27 8:49 ` [PATCH 5.18 05/47] ia64: define get_cycles macro for arch-override Greg Kroah-Hartman
2022-05-27 8:49 ` [PATCH 5.18 06/47] s390: " Greg Kroah-Hartman
2022-05-27 8:49 ` [PATCH 5.18 07/47] parisc: " Greg Kroah-Hartman
2022-05-27 8:49 ` [PATCH 5.18 08/47] alpha: " Greg Kroah-Hartman
2022-05-27 8:49 ` [PATCH 5.18 09/47] powerpc: " Greg Kroah-Hartman
2022-05-27 8:49 ` [PATCH 5.18 10/47] timekeeping: Add raw clock fallback for random_get_entropy() Greg Kroah-Hartman
2022-05-27 8:49 ` [PATCH 5.18 11/47] m68k: use fallback for random_get_entropy() instead of zero Greg Kroah-Hartman
2022-05-27 8:49 ` [PATCH 5.18 12/47] riscv: " Greg Kroah-Hartman
2022-05-27 8:49 ` [PATCH 5.18 13/47] mips: use fallback for random_get_entropy() instead of just c0 random Greg Kroah-Hartman
2022-05-27 8:49 ` Greg Kroah-Hartman [this message]
2022-05-27 8:49 ` [PATCH 5.18 15/47] nios2: use fallback for random_get_entropy() instead of zero Greg Kroah-Hartman
2022-05-27 8:49 ` [PATCH 5.18 16/47] x86/tsc: Use " Greg Kroah-Hartman
2022-05-27 8:49 ` [PATCH 5.18 17/47] um: use " Greg Kroah-Hartman
2022-05-27 8:49 ` [PATCH 5.18 18/47] sparc: " Greg Kroah-Hartman
2022-05-27 8:49 ` [PATCH 5.18 19/47] xtensa: " Greg Kroah-Hartman
2022-05-27 8:50 ` [PATCH 5.18 20/47] random: insist on random_get_entropy() existing in order to simplify Greg Kroah-Hartman
2022-05-27 8:50 ` [PATCH 5.18 21/47] random: do not use batches when !crng_ready() Greg Kroah-Hartman
2022-05-27 8:50 ` [PATCH 5.18 22/47] random: use first 128 bits of input as fast init Greg Kroah-Hartman
2022-05-27 8:50 ` [PATCH 5.18 23/47] random: do not pretend to handle premature next security model Greg Kroah-Hartman
2022-05-27 8:50 ` [PATCH 5.18 24/47] random: order timer entropy functions below interrupt functions Greg Kroah-Hartman
2022-05-27 8:50 ` [PATCH 5.18 25/47] random: do not use input pool from hard IRQs Greg Kroah-Hartman
2022-05-27 8:50 ` [PATCH 5.18 26/47] random: help compiler out with fast_mix() by using simpler arguments Greg Kroah-Hartman
2022-05-27 8:50 ` [PATCH 5.18 27/47] siphash: use one source of truth for siphash permutations Greg Kroah-Hartman
2022-05-27 8:50 ` [PATCH 5.18 28/47] random: use symbolic constants for crng_init states Greg Kroah-Hartman
2022-05-27 8:50 ` [PATCH 5.18 29/47] random: avoid initializing twice in credit race Greg Kroah-Hartman
2022-05-27 8:50 ` [PATCH 5.18 30/47] random: move initialization out of reseeding hot path Greg Kroah-Hartman
2022-05-27 8:50 ` [PATCH 5.18 31/47] random: remove ratelimiting for in-kernel unseeded randomness Greg Kroah-Hartman
2022-05-27 8:50 ` [PATCH 5.18 32/47] random: use proper jiffies comparison macro Greg Kroah-Hartman
2022-05-27 8:50 ` [PATCH 5.18 33/47] random: handle latent entropy and command line from random_init() Greg Kroah-Hartman
2022-05-27 8:50 ` [PATCH 5.18 34/47] random: credit architectural init the exact amount Greg Kroah-Hartman
2022-05-27 8:50 ` [PATCH 5.18 35/47] random: use static branch for crng_ready() Greg Kroah-Hartman
2022-05-27 8:50 ` [PATCH 5.18 36/47] random: remove extern from functions in header Greg Kroah-Hartman
2022-05-27 8:50 ` [PATCH 5.18 37/47] random: use proper return types on get_random_{int,long}_wait() Greg Kroah-Hartman
2022-05-27 8:50 ` [PATCH 5.18 38/47] random: make consistent use of buf and len Greg Kroah-Hartman
2022-05-27 8:50 ` [PATCH 5.18 39/47] random: move initialization functions out of hot pages Greg Kroah-Hartman
2022-05-27 8:50 ` [PATCH 5.18 40/47] random: move randomize_page() into mm where it belongs Greg Kroah-Hartman
2022-05-27 8:50 ` [PATCH 5.18 41/47] random: unify batched entropy implementations Greg Kroah-Hartman
2022-05-27 8:50 ` [PATCH 5.18 42/47] random: convert to using fops->read_iter() Greg Kroah-Hartman
2022-05-27 8:50 ` [PATCH 5.18 43/47] random: convert to using fops->write_iter() Greg Kroah-Hartman
2022-05-27 8:50 ` [PATCH 5.18 44/47] random: wire up fops->splice_{read,write}_iter() Greg Kroah-Hartman
2022-05-27 8:50 ` [PATCH 5.18 45/47] random: check for signals after page of pool writes Greg Kroah-Hartman
2022-05-27 8:50 ` [PATCH 5.18 46/47] ACPI: sysfs: Fix BERT error region memory mapping Greg Kroah-Hartman
2022-05-27 8:50 ` [PATCH 5.18 47/47] ALSA: ctxfi: Add SB046x PCI ID Greg Kroah-Hartman
2022-05-27 22:40 ` [PATCH 5.18 00/47] 5.18.1-rc1 review Guenter Roeck
2022-05-28 1:53 ` Justin Forbes
2022-05-28 2:24 ` Ron Economos
2022-05-28 2:50 ` Bagas Sanjaya
2022-05-28 11:16 ` Naresh Kamboju
2022-05-28 13:39 ` Rudi Heitbaum
2022-05-29 2:48 ` Fox Chen
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