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arm64: Ensure VM_WRITE|VM_SHARED ptes are clean by default

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Shared and writable mappings (__S.1.) should be clean (!dirty) initially
and made dirty on a subsequent write either through the hardware DBM
(dirty bit management) mechanism or through a write page fault. A clean
pte for the arm64 kernel is one that has PTE_RDONLY set and PTE_DIRTY
clear.

The PAGE_SHARED{,_EXEC} attributes have PTE_WRITE set (PTE_DBM) and
PTE_DIRTY clear. Prior to commit 73e86cb03c ("arm64: Move PTE_RDONLY
bit handling out of set_pte_at()"), it was the responsibility of
set_pte_at() to set the PTE_RDONLY bit and mark the pte clean if the
software PTE_DIRTY bit was not set. However, the above commit removed
the pte_sw_dirty() check and the subsequent setting of PTE_RDONLY in
set_pte_at() while leaving the PAGE_SHARED{,_EXEC} definitions
unchanged. The result is that shared+writable mappings are now dirty by
default

Fix the above by explicitly setting PTE_RDONLY in PAGE_SHARED{,_EXEC}.
In addition, remove the superfluous PTE_DIRTY bit from the kernel PROT_*
attributes.

Fixes: 73e86cb03c ("arm64: Move PTE_RDONLY bit handling out of set_pte_at()")
Cc: <stable@vger.kernel.org> # 4.14.x-
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Catalin Marinas 2019-10-29 15:30:51 +00:00 committed by Will Deacon
parent 777d062e5b
commit aa57157be6
1 changed files with 8 additions and 7 deletions
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15
arch/arm64/include/asm/pgtable-prot.h
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@ -32,11 +32,11 @@
#define PROT_DEFAULT (_PROT_DEFAULT | PTE_MAYBE_NG)
#define PROT_SECT_DEFAULT (_PROT_SECT_DEFAULT | PMD_MAYBE_NG)
#define PROT_DEVICE_nGnRnE (PROT_DEFAULT | PTE_PXN | PTE_UXN | PTE_DIRTY | PTE_WRITE | PTE_ATTRINDX(MT_DEVICE_nGnRnE))
#define PROT_DEVICE_nGnRE (PROT_DEFAULT | PTE_PXN | PTE_UXN | PTE_DIRTY | PTE_WRITE | PTE_ATTRINDX(MT_DEVICE_nGnRE))
#define PROT_NORMAL_NC (PROT_DEFAULT | PTE_PXN | PTE_UXN | PTE_DIRTY | PTE_WRITE | PTE_ATTRINDX(MT_NORMAL_NC))
#define PROT_NORMAL_WT (PROT_DEFAULT | PTE_PXN | PTE_UXN | PTE_DIRTY | PTE_WRITE | PTE_ATTRINDX(MT_NORMAL_WT))
#define PROT_NORMAL (PROT_DEFAULT | PTE_PXN | PTE_UXN | PTE_DIRTY | PTE_WRITE | PTE_ATTRINDX(MT_NORMAL))
#define PROT_DEVICE_nGnRnE (PROT_DEFAULT | PTE_PXN | PTE_UXN | PTE_WRITE | PTE_ATTRINDX(MT_DEVICE_nGnRnE))
#define PROT_DEVICE_nGnRE (PROT_DEFAULT | PTE_PXN | PTE_UXN | PTE_WRITE | PTE_ATTRINDX(MT_DEVICE_nGnRE))
#define PROT_NORMAL_NC (PROT_DEFAULT | PTE_PXN | PTE_UXN | PTE_WRITE | PTE_ATTRINDX(MT_NORMAL_NC))
#define PROT_NORMAL_WT (PROT_DEFAULT | PTE_PXN | PTE_UXN | PTE_WRITE | PTE_ATTRINDX(MT_NORMAL_WT))
#define PROT_NORMAL (PROT_DEFAULT | PTE_PXN | PTE_UXN | PTE_WRITE | PTE_ATTRINDX(MT_NORMAL))
#define PROT_SECT_DEVICE_nGnRE (PROT_SECT_DEFAULT | PMD_SECT_PXN | PMD_SECT_UXN | PMD_ATTRINDX(MT_DEVICE_nGnRE))
#define PROT_SECT_NORMAL (PROT_SECT_DEFAULT | PMD_SECT_PXN | PMD_SECT_UXN | PMD_ATTRINDX(MT_NORMAL))
@ -80,8 +80,9 @@
#define PAGE_S2_DEVICE __pgprot(_PROT_DEFAULT | PAGE_S2_MEMATTR(DEVICE_nGnRE) | PTE_S2_RDONLY | PTE_S2_XN)
#define PAGE_NONE __pgprot(((_PAGE_DEFAULT) & ~PTE_VALID) | PTE_PROT_NONE | PTE_RDONLY | PTE_NG | PTE_PXN | PTE_UXN)
#define PAGE_SHARED __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN | PTE_UXN | PTE_WRITE)
#define PAGE_SHARED_EXEC __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN | PTE_WRITE)
/* shared+writable pages are clean by default, hence PTE_RDONLY|PTE_WRITE */
#define PAGE_SHARED __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_RDONLY | PTE_NG | PTE_PXN | PTE_UXN | PTE_WRITE)
#define PAGE_SHARED_EXEC __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_RDONLY | PTE_NG | PTE_PXN | PTE_WRITE)
#define PAGE_READONLY __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_RDONLY | PTE_NG | PTE_PXN | PTE_UXN)
#define PAGE_READONLY_EXEC __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_RDONLY | PTE_NG | PTE_PXN)
#define PAGE_EXECONLY __pgprot(_PAGE_DEFAULT | PTE_RDONLY | PTE_NG | PTE_PXN)