• Catalin Marinas's avatar
    arm64: Revert support for execute-only user mappings · 24cecc37
    Catalin Marinas authored
    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 cab15ce6 ("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: cab15ce6 ("arm64: Introduce execute-only page access permissions")
    Cc: <stable@vger.kernel.org> # 4.9.x-
    Acked-by: default avatarWill Deacon <will@kernel.org>
    Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    24cecc37
pgtable.h 25.2 KB