Messages in this thread | | | Date | Fri, 4 Feb 2022 18:44:11 +0000 | From | Catalin Marinas <> | Subject | Re: [PATCH] [PATCH v4] arm64/mm: avoid fixmap race condition when create pud mapping |
| |
On Tue, Feb 01, 2022 at 07:44:00PM +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(). 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>
This looks fine to me but I'd rather leave it in -next for a bit given that we attempted to fix it a couple of times and got it wrong.
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
| |