| From 66f133ceab7456c789f70a242991ed1b27ba1c3d Mon Sep 17 00:00:00 2001 |
| From: Max Filippov <jcmvbkbc@gmail.com> |
| Date: Fri, 8 Apr 2022 13:08:55 -0700 |
| Subject: highmem: fix checks in __kmap_local_sched_{in,out} |
| |
| From: Max Filippov <jcmvbkbc@gmail.com> |
| |
| commit 66f133ceab7456c789f70a242991ed1b27ba1c3d upstream. |
| |
| 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> |
| Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| mm/highmem.c | 4 ++-- |
| 1 file changed, 2 insertions(+), 2 deletions(-) |
| |
| --- 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))) |