From f43c27188a49111b58e9611afa2f0365b0b55625 Mon Sep 17 00:00:00 2001 From: Lorenzo Pieralisi Date: Fri, 19 Dec 2014 17:03:47 +0000 Subject: 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: 95322526ef62 ("arm64: kernel: cpu_{suspend/resume} implementation") Cc: # 3.14+: 18ab7db Cc: # 3.14+: 714f599 Cc: # 3.14+: c3684fb Cc: # 3.14+ Cc: Will Deacon Signed-off-by: Lorenzo Pieralisi Signed-off-by: Catalin Marinas --- arch/arm64/kernel/suspend.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) (limited to 'arch') diff --git a/arch/arm64/kernel/suspend.c b/arch/arm64/kernel/suspend.c index 3771b72b6569..2d6b6065fe7f 100644 --- a/arch/arm64/kernel/suspend.c +++ b/arch/arm64/kernel/suspend.c @@ -5,6 +5,7 @@ #include #include #include +#include #include #include #include @@ -98,7 +99,18 @@ int __cpu_suspend(unsigned long arg, int (*fn)(unsigned long)) */ ret = __cpu_suspend_enter(arg, fn); if (ret == 0) { - cpu_switch_mm(mm->pgd, mm); + /* + * We are resuming from reset with TTBR0_EL1 set to the + * idmap to enable the MMU; restore the active_mm mappings in + * TTBR0_EL1 unless the active_mm == &init_mm, in which case + * the thread entered __cpu_suspend with TTBR0_EL1 set to + * reserved TTBR0 page tables and should be restored as such. + */ + if (mm == &init_mm) + cpu_set_reserved_ttbr0(); + else + cpu_switch_mm(mm->pgd, mm); + flush_tlb_all(); /* -- cgit v1.2.3-59-g8ed1b