diff mbox series

[2/9] highmem: fix checks in __kmap_local_sched_{in,out}

Message ID 20220408200856.602F9C385A6@smtp.kernel.org (mailing list archive)
State New
Headers show
Series [1/9] mm: migrate: use thp_order instead of HPAGE_PMD_ORDER for new page allocation. | expand

Commit Message

Andrew Morton April 8, 2022, 8:08 p.m. UTC 
From: Max Filippov <jcmvbkbc@gmail.com>
Subject: highmem: fix checks in __kmap_local_sched_{in,out}

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.

Link: https://lkml.kernel.org/r/20220403235159.3498065-1-jcmvbkbc@gmail.com
Fixes: 5fbda3ecd14a ("sched: highmem: Store local kmaps in task struct")
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/highmem.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
diff mbox series

Patch

--- a/mm/highmem.c~highmem-fix-checks-in-__kmap_local_sched_inout
+++ a/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)))