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From: paulmck@kernel.org
To: linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com,
	kernel-team@fb.com, mingo@kernel.org
Cc: elver@google.com, andreyknvl@google.com, glider@google.com,
	dvyukov@google.com, cai@lca.pw, boqun.feng@gmail.com,
	"Paul E . McKenney" <paulmck@kernel.org>
Subject: [PATCH tip/core/rcu 02/10] x86/mm/pat: Mark an intentional data race
Date: Mon, 22 Jun 2020 17:43:25 -0700	[thread overview]
Message-ID: <20200623004333.27227-2-paulmck@kernel.org> (raw)
In-Reply-To: <20200623003731.GA26717@paulmck-ThinkPad-P72>

From: Qian Cai <cai@lca.pw>

cpa_4k_install could be accessed concurrently as noticed by KCSAN,

read to 0xffffffffaa59a000 of 8 bytes by interrupt on cpu 7:
cpa_inc_4k_install arch/x86/mm/pat/set_memory.c:131 [inline]
__change_page_attr+0x10cf/0x1840 arch/x86/mm/pat/set_memory.c:1514
__change_page_attr_set_clr+0xce/0x490 arch/x86/mm/pat/set_memory.c:1636
__set_pages_np+0xc4/0xf0 arch/x86/mm/pat/set_memory.c:2148
__kernel_map_pages+0xb0/0xc8 arch/x86/mm/pat/set_memory.c:2178
kernel_map_pages include/linux/mm.h:2719 [inline] <snip>

write to 0xffffffffaa59a000 of 8 bytes by task 1 on cpu 6:
cpa_inc_4k_install arch/x86/mm/pat/set_memory.c:131 [inline]
__change_page_attr+0x10ea/0x1840 arch/x86/mm/pat/set_memory.c:1514
__change_page_attr_set_clr+0xce/0x490 arch/x86/mm/pat/set_memory.c:1636
__set_pages_p+0xc4/0xf0 arch/x86/mm/pat/set_memory.c:2129
__kernel_map_pages+0x2e/0xc8 arch/x86/mm/pat/set_memory.c:2176
kernel_map_pages include/linux/mm.h:2719 [inline] <snip>

Both accesses are due to the same "cpa_4k_install++" in
cpa_inc_4k_install. A data race here could be potentially undesirable:
depending on compiler optimizations or how x86 executes a non-LOCK'd
increment, it may lose increments, corrupt the counter, etc. Since this
counter only seems to be used for printing some stats, this data race
itself is unlikely to cause harm to the system though. Thus, mark this
intentional data race using the data_race() marco.

Suggested-by: Macro Elver <elver@google.com>
Signed-off-by: Qian Cai <cai@lca.pw>
Acked-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 arch/x86/mm/pat/set_memory.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index 77e0430..d1b2a88 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -135,7 +135,7 @@ static inline void cpa_inc_2m_checked(void)
 
 static inline void cpa_inc_4k_install(void)
 {
-	cpa_4k_install++;
+	data_race(cpa_4k_install++);
 }
 
 static inline void cpa_inc_lp_sameprot(int level)
-- 
2.9.5


  parent reply	other threads:[~2020-06-23  0:44 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-23  0:37 [PATCH tip/core/rcu 0/23] Torture-test updates for v5.9 Paul E. McKenney
2020-06-23  0:37 ` [PATCH tip/core/rcu 01/23] torture: Remove qemu dependency on EFI firmware paulmck
2020-06-23  0:37 ` [PATCH tip/core/rcu 02/23] torture: Add script to smoke-test commits in a branch paulmck
2020-06-23  0:37 ` [PATCH tip/core/rcu 03/23] locktorture: Use true and false to assign to bool variables paulmck
2020-06-23  0:37 ` [PATCH tip/core/rcu 04/23] rcutorture: Add races with task-exit processing paulmck
2020-06-23  0:37 ` [PATCH tip/core/rcu 05/23] torture: Set configfile variable to current scenario paulmck
2020-06-23  0:37 ` [PATCH tip/core/rcu 06/23] rcutorture: Handle non-statistic bang-string error messages paulmck
2020-06-23  0:37 ` [PATCH tip/core/rcu 07/23] rcutorture: NULL rcu_torture_current earlier in cleanup code paulmck
2020-06-23  0:37 ` [PATCH tip/core/rcu 08/23] torture: Remove whitespace from identify_qemu_vcpus output paulmck
2020-06-23  0:37 ` [PATCH tip/core/rcu 09/23] torture: Add --allcpus argument to the kvm.sh script paulmck
2020-06-23  0:37 ` [PATCH tip/core/rcu 10/23] rcu/rcutorture: Replace 0 with false paulmck
2020-06-23  0:37 ` [PATCH tip/core/rcu 11/23] torture: Create qemu-cmd in --buildonly runs paulmck
2020-06-23  0:37 ` [PATCH tip/core/rcu 12/23] torture: Add a stop-run capability paulmck
2020-06-23  0:37 ` [PATCH tip/core/rcu 13/23] torture: Abstract out console-log error detection paulmck
2020-06-23  0:37 ` [PATCH tip/core/rcu 14/23] rcutorture: Check for unwatched readers paulmck
2020-06-23  0:37 ` [PATCH tip/core/rcu 15/23] torture: Pass --kmake-arg to all make invocations paulmck
2020-06-23  0:37 ` [PATCH tip/core/rcu 16/23] torture: Correctly summarize build-only runs paulmck
2020-06-23  0:37 ` [PATCH tip/core/rcu 17/23] torture: Improve diagnostic for KCSAN-incapable compilers paulmck
2020-06-23  0:37 ` [PATCH tip/core/rcu 18/23] torture: Add more tracing crib notes to kvm.sh paulmck
2020-06-23  0:37 ` [PATCH tip/core/rcu 19/23] torture: Add kvm-tranform.sh script for qemu-cmd files paulmck
2020-06-23  0:37 ` [PATCH tip/core/rcu 20/23] torture: Dump ftrace at shutdown only if requested paulmck
2020-06-23  0:37 ` [PATCH tip/core/rcu 21/23] torture: Avoid duplicate specification of qemu command paulmck
2020-06-23  0:37 ` [PATCH tip/core/rcu 22/23] torture: Remove obsolete "cd $KVM" paulmck
2020-06-23  0:37 ` [PATCH tip/core/rcu 23/23] rcutorture: Remove KCSAN stubs paulmck
2020-06-23  0:43 ` [PATCH tip/core/rcu 01/10] fork: Annotate a data race in vm_area_dup() paulmck
2020-06-23  0:43 ` paulmck [this message]
2020-06-23  0:43 ` [PATCH tip/core/rcu 03/10] rculist: Add ASSERT_EXCLUSIVE_ACCESS() to __list_splice_init_rcu() paulmck
2020-06-23  0:43 ` [PATCH tip/core/rcu 04/10] kcsan: Add test suite paulmck
2020-06-23  0:43 ` [PATCH tip/core/rcu 05/10] locking/osq_lock: Annotate a data race in osq_lock paulmck
2020-06-23  0:43 ` [PATCH tip/core/rcu 06/10] kcsan: Prefer '__no_kcsan inline' in test paulmck
2020-06-23  0:43 ` [PATCH tip/core/rcu 07/10] kcsan: Silence -Wmissing-prototypes warning with W=1 paulmck
2020-06-23  0:43 ` [PATCH tip/core/rcu 08/10] kcsan: Rename test.c to selftest.c paulmck
2020-06-23  0:43 ` [PATCH tip/core/rcu 09/10] kcsan: Remove existing special atomic rules paulmck
2020-06-23  0:43 ` [PATCH tip/core/rcu 10/10] kcsan: Add jiffies test to test suite paulmck

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