]> git.proxmox.com Git - mirror_ubuntu-kernels.git/commit
arm64: kernel: fix __cpu_suspend mm switch on warm-boot
authorLorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Fri, 19 Dec 2014 17:03:47 +0000 (17:03 +0000)
committerCatalin Marinas <catalin.marinas@arm.com>
Tue, 23 Dec 2014 16:38:50 +0000 (16:38 +0000)
commitf43c27188a49111b58e9611afa2f0365b0b55625
treec6754b45630fd0278d3a52222a1721f9d0dd4d30
parent31dde116cb084bc0042cafe48975ffb7d1a4ae5d
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: <stable@vger.kernel.org> # 3.14+: 18ab7db
Cc: <stable@vger.kernel.org> # 3.14+: 714f599
Cc: <stable@vger.kernel.org> # 3.14+: c3684fb
Cc: <stable@vger.kernel.org> # 3.14+
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
arch/arm64/kernel/suspend.c