From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:38598 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751092AbdFZGn7 (ORCPT ); Mon, 26 Jun 2017 02:43:59 -0400 Subject: Patch "random: silence compiler warnings and fix race" has been added to the 4.11-stable tree To: Jason@zx2c4.com, gregkh@linuxfoundation.org, tytso@mit.edu Cc: , From: Date: Mon, 26 Jun 2017 08:15:40 +0200 Message-ID: <1498457740245253@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled random: silence compiler warnings and fix race to the 4.11-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: random-silence-compiler-warnings-and-fix-race.patch and it can be found in the queue-4.11 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 4a072c71f49b0a0e495ea13423bdb850da73c58c Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Thu, 15 Jun 2017 00:45:26 +0200 Subject: random: silence compiler warnings and fix race From: Jason A. Donenfeld commit 4a072c71f49b0a0e495ea13423bdb850da73c58c upstream. Odd versions of gcc for the sh4 architecture will actually warn about flags being used while uninitialized, so we set them to zero. Non crazy gccs will optimize that out again, so it doesn't make a difference. Next, over aggressive gccs could inline the expression that defines use_lock, which could then introduce a race resulting in a lock imbalance. By using READ_ONCE, we prevent that fate. Finally, we make that assignment const, so that gcc can still optimize a nice amount. Finally, we fix a potential deadlock between primary_crng.lock and batched_entropy_reset_lock, where they could be called in opposite order. Moving the call to invalidate_batched_entropy to outside the lock rectifies this issue. Fixes: b169c13de473a85b3c859bb36216a4cb5f00a54a Signed-off-by: Jason A. Donenfeld Signed-off-by: Theodore Ts'o Signed-off-by: Greg Kroah-Hartman --- drivers/char/random.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -803,13 +803,13 @@ static int crng_fast_load(const char *cp p[crng_init_cnt % CHACHA20_KEY_SIZE] ^= *cp; cp++; crng_init_cnt++; len--; } + spin_unlock_irqrestore(&primary_crng.lock, flags); if (crng_init_cnt >= CRNG_INIT_CNT_THRESH) { invalidate_batched_entropy(); crng_init = 1; wake_up_interruptible(&crng_init_wait); pr_notice("random: fast init done\n"); } - spin_unlock_irqrestore(&primary_crng.lock, flags); return 1; } @@ -841,6 +841,7 @@ static void crng_reseed(struct crng_stat } memzero_explicit(&buf, sizeof(buf)); crng->init_time = jiffies; + spin_unlock_irqrestore(&primary_crng.lock, flags); if (crng == &primary_crng && crng_init < 2) { invalidate_batched_entropy(); crng_init = 2; @@ -848,7 +849,6 @@ static void crng_reseed(struct crng_stat wake_up_interruptible(&crng_init_wait); pr_notice("random: crng init done\n"); } - spin_unlock_irqrestore(&primary_crng.lock, flags); } static inline void crng_wait_ready(void) @@ -2037,8 +2037,8 @@ static DEFINE_PER_CPU(struct batched_ent u64 get_random_u64(void) { u64 ret; - bool use_lock = crng_init < 2; - unsigned long flags; + bool use_lock = READ_ONCE(crng_init) < 2; + unsigned long flags = 0; struct batched_entropy *batch; #if BITS_PER_LONG == 64 @@ -2069,8 +2069,8 @@ static DEFINE_PER_CPU(struct batched_ent u32 get_random_u32(void) { u32 ret; - bool use_lock = crng_init < 2; - unsigned long flags; + bool use_lock = READ_ONCE(crng_init) < 2; + unsigned long flags = 0; struct batched_entropy *batch; if (arch_get_random_int(&ret)) Patches currently in stable-queue which might be from Jason@zx2c4.com are queue-4.11/random-silence-compiler-warnings-and-fix-race.patch