Messages in this thread | | | Date | Wed, 5 Jan 2022 18:03:57 +0000 | From | Catalin Marinas <> | Subject | Re: [PATCH v3] arm64/mm: avoid fixmap race condition when create pud mapping |
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On Thu, Dec 16, 2021 at 04:28:12PM +0800, Jianyong Wu wrote: > 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(). > > Signed-off-by: Jianyong Wu <jianyong.wu@arm.com>
I tried to queue this patch but with certain configurations it doesn't boot under Qemu. Starting from defconfig, update .config with (I had this in one of my build scripts):
$ ./scripts/config \ -e DEBUG_KERNEL \ -e DEBUG_PAGEALLOC \ -e DEBUG_PAGEALLOC_ENABLE_DEFAULT \ -e DEBUG_WX \ -e DEBUG_SET_MODULE_RONX \ -e DEBUG_ALIGN_RODATA \ -e ARM64_PTDUMP_DEBUGFS \ -e DEBUG_OBJECTS \ -e DEBUG_OBJECTS_FREE \ -e DEBUG_OBJECTS_TIMERS \ -e DEBUG_KOBJECT_RELEASE \ -e DEBUG_LOCKING_API_SELFTESTS \ -e DEBUG_PREEMPT \ -e DEBUG_TIMEKEEPING \ -e DEBUG_VM \ -e DEBUG_VM_VMACACHE \ -e DEBUG_VM_RB \ -e DEBUG_VM_PGFLAGS \ -e DEBUG_VIRTUAL \ -e DEBUG_LIST \ -e DEBUG_PI_LIST \ -e DEBUG_SG \ -e PROVE_LOCKING \ -e DEBUG_RT_MUTEXES \ -e DEBUG_ATOMIC_SLEEP \ -e ATOMIC64_SELFTEST
It stop after exiting the EFI boot services. I did not have time to debug.
-- Catalin
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