From: Max Filippov <jcmvbkbc@gmail.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Max Filippov <jcmvbkbc@gmail.com>
Subject: [PATCH] highmem: fix checks in __kmap_local_sched_{in,out}
Date: Sun, 3 Apr 2022 16:51:59 -0700 [thread overview]
Message-ID: <20220403235159.3498065-1-jcmvbkbc@gmail.com> (raw)
When CONFIG_DEBUG_KMAP_LOCAL is enabled __kmap_local_sched_{in,out}
check that even slots in the tsk->kmap_ctrl.pteval are unmapped. The
slots are initialized with 0 value, but the check is done with pte_none.
0 pte however does not necessarily mean that pte_none will return true.
e.g. on xtensa it returns false, resulting in the following runtime
warnings:
WARNING: CPU: 0 PID: 101 at mm/highmem.c:627 __kmap_local_sched_out+0x51/0x108
CPU: 0 PID: 101 Comm: touch Not tainted 5.17.0-rc7-00010-gd3a1cdde80d2-dirty #13
Call Trace:
dump_stack+0xc/0x40
__warn+0x8f/0x174
warn_slowpath_fmt+0x48/0xac
__kmap_local_sched_out+0x51/0x108
__schedule+0x71a/0x9c4
preempt_schedule_irq+0xa0/0xe0
common_exception_return+0x5c/0x93
do_wp_page+0x30e/0x330
handle_mm_fault+0xa70/0xc3c
do_page_fault+0x1d8/0x3c4
common_exception+0x7f/0x7f
WARNING: CPU: 0 PID: 101 at mm/highmem.c:664 __kmap_local_sched_in+0x50/0xe0
CPU: 0 PID: 101 Comm: touch Tainted: G W 5.17.0-rc7-00010-gd3a1cdde80d2-dirty #13
Call Trace:
dump_stack+0xc/0x40
__warn+0x8f/0x174
warn_slowpath_fmt+0x48/0xac
__kmap_local_sched_in+0x50/0xe0
finish_task_switch$isra$0+0x1ce/0x2f8
__schedule+0x86e/0x9c4
preempt_schedule_irq+0xa0/0xe0
common_exception_return+0x5c/0x93
do_wp_page+0x30e/0x330
handle_mm_fault+0xa70/0xc3c
do_page_fault+0x1d8/0x3c4
common_exception+0x7f/0x7f
Fix it by replacing !pte_none(pteval) with pte_val(pteval) != 0.
Fixes: 5fbda3ecd14a ("sched: highmem: Store local kmaps in task struct")
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
---
mm/highmem.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/mm/highmem.c b/mm/highmem.c
index 762679050c9a..916b66e0776c 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -624,7 +624,7 @@ void __kmap_local_sched_out(void)
/* With debug all even slots are unmapped and act as guard */
if (IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL) && !(i & 0x01)) {
- WARN_ON_ONCE(!pte_none(pteval));
+ WARN_ON_ONCE(pte_val(pteval) != 0);
continue;
}
if (WARN_ON_ONCE(pte_none(pteval)))
@@ -661,7 +661,7 @@ void __kmap_local_sched_in(void)
/* With debug all even slots are unmapped and act as guard */
if (IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL) && !(i & 0x01)) {
- WARN_ON_ONCE(!pte_none(pteval));
+ WARN_ON_ONCE(pte_val(pteval) != 0);
continue;
}
if (WARN_ON_ONCE(pte_none(pteval)))
--
2.30.2
next reply other threads:[~2022-04-03 23:52 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-03 23:51 Max Filippov [this message]
2022-04-04 15:12 ` Thomas Gleixner
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