Commit 9163f011 authored by Anshuman Khandual's avatar Anshuman Khandual Committed by Will Deacon
Browse files

arm64/mm: Fix ttbr0 values stored in struct thread_info for software-pan 



When using CONFIG_ARM64_SW_TTBR0_PAN, a task's thread_info::ttbr0 must be
the TTBR0_EL1 value used to run userspace. With 52-bit PAs, the PA must be
packed into the TTBR using phys_to_ttbr(), but we forget to do this in some
of the SW PAN code. Thus, if the value is installed into TTBR0_EL1 (as may
happen in the uaccess routines), this could result in UNPREDICTABLE
behaviour.

Since hardware with 52-bit PA support almost certainly has HW PAN, which
will be used in preference, this shouldn't be a practical issue, but let's
fix this for consistency.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Fixes: 529c4b05 ("arm64: handle 52-bit addresses in TTBR")
Signed-off-by: default avatarAnshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/1623749578-11231-1-git-send-email-anshuman.khandual@arm.com


Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent 84c5e23e

arch/arm64/include/asm/mmu_context.h

+2 −2
Original line number Diff line number Diff line
@@ -177,9 +177,9 @@ static inline void update_saved_ttbr0(struct task_struct *tsk, 
		return;



	if (mm == &init_mm)

		ttbr = __pa_symbol(reserved_pg_dir);

		ttbr = phys_to_ttbr(__pa_symbol(reserved_pg_dir));

	else

		ttbr = virt_to_phys(mm->pgd) | ASID(mm) << 48;

		ttbr = phys_to_ttbr(virt_to_phys(mm->pgd)) | ASID(mm) << 48;



	WRITE_ONCE(task_thread_info(tsk)->ttbr0, ttbr);

}

arch/arm64/kernel/setup.c

+1 −1
Original line number Diff line number Diff line
@@ -381,7 +381,7 @@ void __init __no_sanitize_address setup_arch(char **cmdline_p) 
	 * faults in case uaccess_enable() is inadvertently called by the init

	 * thread.

	 */

	init_task.thread_info.ttbr0 = __pa_symbol(reserved_pg_dir);

	init_task.thread_info.ttbr0 = phys_to_ttbr(__pa_symbol(reserved_pg_dir));

#endif



	if (boot_args[1] || boot_args[2] || boot_args[3]) {