diff mbox

[PATCHv2,1/2] arm64: mm: detect bad __create_mapping uses

Message ID 1448285180-15389-1-git-send-email-mark.rutland@arm.com
State Accepted
Commit cc5d2b3b95cdbb3fed4e38e667d17b9ac7250f7a
Headers show

Commit Message

Mark Rutland Nov. 23, 2015, 1:26 p.m. UTC 
If a caller of __create_mapping provides a PA and VA which have
different sub-page offsets, it is not clear which offset they expect to
apply to the mapping, and is indicative of a bad caller.

In some cases, the region we wish to map may validly have a sub-page
offset in the physical and virtual addresses. For example, EFI runtime
regions have 4K granularity, yet may be mapped by a 64K page kernel. So
long as the physical and virtual offsets are the same, the region will
be mapped at the expected VAs.

Disallow calls with differing sub-page offsets, and WARN when they are
encountered, so that we can detect and fix such cases.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>

Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

Reviewed-by: Steve Capper <steve.capper@linaro.org>

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Laura Abbott <labbott@fedoraproject.org>
Cc: Will Deacon <will.deacon@arm.com>
---
 arch/arm64/mm/mmu.c | 7 +++++++
 1 file changed, 7 insertions(+)

Since v1 [1]:
* Describe why we permit sub-page offsets.
* Fix Catalin's email address.
* Add acks.

[1] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-November/386930.html

-- 
1.9.1


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Comments

Catalin Marinas Nov. 26, 2015, 6:17 p.m. UTC | #1 
On Mon, Nov 23, 2015 at 01:26:19PM +0000, Mark Rutland wrote:
> If a caller of __create_mapping provides a PA and VA which have

> different sub-page offsets, it is not clear which offset they expect to

> apply to the mapping, and is indicative of a bad caller.

> 

> In some cases, the region we wish to map may validly have a sub-page

> offset in the physical and virtual addresses. For example, EFI runtime

> regions have 4K granularity, yet may be mapped by a 64K page kernel. So

> long as the physical and virtual offsets are the same, the region will

> be mapped at the expected VAs.

> 

> Disallow calls with differing sub-page offsets, and WARN when they are

> encountered, so that we can detect and fix such cases.

> 

> Signed-off-by: Mark Rutland <mark.rutland@arm.com>

> Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

> Reviewed-by: Steve Capper <steve.capper@linaro.org>

> Cc: Catalin Marinas <catalin.marinas@arm.com>

> Cc: Laura Abbott <labbott@fedoraproject.org>

> Cc: Will Deacon <will.deacon@arm.com>


On both patches:

Acked-by: Catalin Marinas <catalin.marinas@arm.com>


Since they don't look urgent, I'll leave them to Will for 4.5.

-- 
Catalin

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diff mbox

Patch

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index abb66f8..2250d89 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -300,6 +300,13 @@  static void  __create_mapping(struct mm_struct *mm, pgd_t *pgd,
 {
 	unsigned long addr, length, end, next;
 
+	/*
+	 * If the virtual and physical address don't have the same offset
+	 * within a page, we cannot map the region as the caller expects.
+	 */
+	if (WARN_ON((phys ^ virt) & ~PAGE_MASK))
+		return;
+
 	addr = virt & PAGE_MASK;
 	length = PAGE_ALIGN(size + (virt & ~PAGE_MASK));