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From: Rick Edgecombe <rick.p.edgecombe@intel.com>
To: dave.hansen@intel.com, luto@kernel.org, peterz@infradead.org,
	x86@kernel.org, akpm@linux-foundation.org, keescook@chromium.org,
	shakeelb@google.com, vbabka@suse.cz, rppt@kernel.org
Cc: Rick Edgecombe <rick.p.edgecombe@intel.com>,
	linux-mm@kvack.org, linux-hardening@vger.kernel.org,
	kernel-hardening@lists.openwall.com, ira.weiny@intel.com,
	dan.j.williams@intel.com, linux-kernel@vger.kernel.org
Subject: [RFC PATCH v2 04/19] mm: Explicitly zero page table lock ptr
Date: Mon, 30 Aug 2021 16:59:12 -0700	[thread overview]
Message-ID: <20210830235927.6443-5-rick.p.edgecombe@intel.com> (raw)
In-Reply-To: <20210830235927.6443-1-rick.p.edgecombe@intel.com>

In ptlock_init() there is a VM_BUG_ON_PAGE() check on the page table lock
pointer. Explicitly zero the lock in ptlock_free() so a page table lock
can be re-initialized without triggering the BUG_ON().

It appears this doesn't normally trigger because the private field
shares the same space in struct page as ptl and page tables always
return to the buddy allocator before being re-initialized as new page
tables. When the page returns to the buddy allocator, private gets
used to store the page order, so it inadvertently clears ptl as well.
In future patches, pages will get re-initialized as page tables without
returning to the buddy allocator so this is needed.

Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
---
 mm/memory.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/memory.c b/mm/memory.c
index 25fc46e87214..e6d630463c7f 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -5465,5 +5465,6 @@ bool ptlock_alloc(struct page *page)
 void ptlock_free(struct page *page)
 {
 	kmem_cache_free(page_ptl_cachep, page->ptl);
+	page->ptl = 0;
 }
 #endif
-- 
2.17.1


  parent reply	other threads:[~2021-08-31  0:00 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-30 23:59 [RFC PATCH v2 00/19] PKS write protected page tables Rick Edgecombe
2021-08-30 23:59 ` [RFC PATCH v2 01/19] list: Support getting most recent element in list_lru Rick Edgecombe
2021-08-30 23:59 ` [RFC PATCH v2 02/19] list: Support list head not in object for list_lru Rick Edgecombe
2021-08-30 23:59 ` [RFC PATCH v2 03/19] x86/mm/cpa: Add grouped page allocations Rick Edgecombe
2021-08-30 23:59 ` Rick Edgecombe [this message]
2021-08-30 23:59 ` [RFC PATCH v2 05/19] x86, mm: Use cache of page tables Rick Edgecombe
2021-08-31  8:40   ` Mike Rapoport
2021-08-31 19:09     ` Edgecombe, Rick P
2021-08-30 23:59 ` [RFC PATCH v2 06/19] x86/mm/cpa: Add perm callbacks to grouped pages Rick Edgecombe
2021-08-30 23:59 ` [RFC PATCH v2 07/19] x86/cpufeatures: Add feature for pks tables Rick Edgecombe
2021-08-30 23:59 ` [RFC PATCH v2 08/19] x86/mm/cpa: Add get_grouped_page_atomic() Rick Edgecombe
2021-08-30 23:59 ` [RFC PATCH v2 09/19] x86/mm: Support GFP_ATOMIC in alloc_table_node() Rick Edgecombe
2021-08-31  8:32   ` Mike Rapoport
2021-08-30 23:59 ` [RFC PATCH v2 10/19] x86/mm: Use alloc_table() for fill_pte(), etc Rick Edgecombe
2021-08-31  8:47   ` Mike Rapoport
2021-08-31 18:48     ` Edgecombe, Rick P
2021-08-30 23:59 ` [RFC PATCH v2 11/19] mm/sparsemem: Use alloc_table() for table allocations Rick Edgecombe
2021-08-31  8:55   ` Mike Rapoport
2021-08-31 18:25     ` Edgecombe, Rick P
2021-09-01  7:22       ` Mike Rapoport
2021-09-02 13:56         ` Vlastimil Babka
2021-08-30 23:59 ` [RFC PATCH v2 12/19] x86/mm: Use free_table in unmap path Rick Edgecombe
2021-08-30 23:59 ` [RFC PATCH v2 13/19] mm/debug_vm_page_table: Use setters instead of WRITE_ONCE Rick Edgecombe
2021-08-30 23:59 ` [RFC PATCH v2 14/19] x86/efi: Toggle table protections when copying Rick Edgecombe
2021-08-30 23:59 ` [RFC PATCH v2 15/19] x86/mm/cpa: Add set_memory_pks() Rick Edgecombe
2021-08-30 23:59 ` [RFC PATCH v2 16/19] x86/mm: Protect page tables with PKS Rick Edgecombe
2021-08-31  8:56   ` Mike Rapoport
2021-08-31 17:55     ` Edgecombe, Rick P
2021-08-30 23:59 ` [RFC PATCH v2 17/19] x86/mm/cpa: PKS protect direct map page tables Rick Edgecombe
2021-08-31 10:14   ` Mike Rapoport
2021-08-31 17:58     ` Edgecombe, Rick P
2021-08-30 23:59 ` [RFC PATCH v2 18/19] x86/mm: Add PKS table soft mode Rick Edgecombe
2021-08-31  3:49   ` Randy Dunlap
2021-08-31 17:55     ` Edgecombe, Rick P
2021-08-30 23:59 ` [RFC PATCH v2 19/19] x86/mm: Add PKS table debug checking Rick Edgecombe

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