arm64: kernel: fix __cpu_suspend mm switch on warm-boot
On arm64 the TTBR0_EL1 register is set to either the reserved TTBR0 page tables on boot or to the active_mm mappings belonging to user space processes, it must never be set to swapper_pg_dir page tables mappings. When a CPU is booted its active_mm is set to init_mm even though its TTBR0_EL1 points at the reserved TTBR0 page mappings. This implies that when __cpu_suspend is triggered the active_mm can point at init_mm even if the current TTBR0_EL1 register contains the reserved TTBR0_EL1 mappings. Therefore, the mm save and restore executed in __cpu_suspend might turn out to be erroneous in that, if the current->active_mm corresponds to init_mm, on resume from low power it ends up restoring in the TTBR0_EL1 the init_mm mappings that are global and can cause speculation of TLB entries which end up being propagated to user space. This patch fixes the issue by checking the active_mm pointer before restoring the TTBR0 mappings. If the current active_mm == &init_mm, the code sets the TTBR0_EL1 to the reserved TTBR0 mapping instead of switching back to the active_mm, which is the expected behaviour corresponding to the TTBR0_EL1 settings when __cpu_suspend was entered. Fixes: 95322526 ("arm64: kernel: cpu_{suspend/resume} implementation") Cc: <stable@vger.kernel.org> # 3.14+: 18ab7db6 Cc: <stable@vger.kernel.org> # 3.14+: 714f5992 Cc: <stable@vger.kernel.org> # 3.14+: c3684fbb Cc: <stable@vger.kernel.org> # 3.14+ Cc: Will Deacon <will.deacon@arm.com> Signed-off-by: NLorenzo Pieralisi <lorenzo.pieralisi@arm.com> Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>
Showing
想要评论请 注册 或 登录