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arm64: Revert support for execute-only user mappings

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commit 24cecc3774 upstream.

The ARMv8 64-bit architecture supports execute-only user permissions by
clearing the PTE_USER and PTE_UXN bits, practically making it a mostly
privileged mapping but from which user running at EL0 can still execute.

The downside, however, is that the kernel at EL1 inadvertently reading
such mapping would not trip over the PAN (privileged access never)
protection.

Revert the relevant bits from commit cab15ce604 ("arm64: Introduce
execute-only page access permissions") so that PROT_EXEC implies
PROT_READ (and therefore PTE_USER) until the architecture gains proper
support for execute-only user mappings.

Fixes: cab15ce604 ("arm64: Introduce execute-only page access permissions")
Cc: <stable@vger.kernel.org> # 4.9.x-
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Catalin Marinas
2020-01-06 14:35:39 +00:00
committed by Greg Kroah-Hartman
parent b9227aacdc
commit d89a351b08
4 changed files with 6 additions and 17 deletions
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2
arch/arm64/mm/fault.c
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@@ -428,7 +428,7 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
struct mm_struct *mm;
struct siginfo si;
vm_fault_t fault, major = 0;
unsigned long vm_flags = VM_READ | VM_WRITE;
unsigned long vm_flags = VM_READ | VM_WRITE | VM_EXEC;
unsigned int mm_flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
if (notify_page_fault(regs, esr))