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Jianyong Wu c17eb1586c arm64/mm: avoid fixmap race condition when create pud mapping

[ Upstream commit ee017ee353506fcec58e481673e4331ff198a80e ]

The 'fixmap' is a global resource and is used recursively by
create pud mapping(), leading to a potential race condition in the
presence of a concurrent call to alloc_init_pud():

kernel_init thread                          virtio-mem workqueue thread
==================                          ===========================

  alloc_init_pud(...)                       alloc_init_pud(...)
  pudp = pud_set_fixmap_offset(...)         pudp = pud_set_fixmap_offset(...)
  READ_ONCE(*pudp)
  pud_clear_fixmap(...)
                                            READ_ONCE(*pudp) // CRASH!

As kernel may sleep during creating pud mapping, introduce a mutex lock to
serialise use of the fixmap entries by alloc_init_pud(). However, there is
no need for locking in early boot stage and it doesn't work well with
KASLR enabled when early boot. So, enable lock when system_state doesn't
equal to "SYSTEM_BOOTING".

Signed-off-by: Jianyong Wu <jianyong.wu@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Fixes: f4710445458c ("arm64: mm: use fixmap when creating page tables")
Link: https://lore.kernel.org/r/20220201114400.56885-1-jianyong.wu@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

2022-04-08 14:23:06 +02:00

alpha

alpha: enable GENERIC_PCI_IOMAP unconditionally

2021-09-19 10:37:00 -07:00

arc

signal: Replace force_sigsegv(SIGSEGV) with force_fatal_sig(SIGSEGV)

2021-11-25 09:49:06 +01:00

arm

ARM: dts: exynos: add missing HDMI supplies on SMDK5420

2022-04-08 14:23:00 +02:00

arm64

arm64/mm: avoid fixmap race condition when create pud mapping