CVE-2024-35818

In the Linux kernel, the following vulnerability has been resolved:
LoongArch: Define the __io_aw() hook as mmiowb() Commit
fb24ea52f78e0d595852e (“drivers: Remove explicit invocations of mmiowb()”)
remove all mmiowb() in drivers, but it says: “NOTE: mmiowb() has only ever
guaranteed ordering in conjunction with spin_unlock(). However, pairing
each mmiowb() removal in this patch with the corresponding call to
spin_unlock() is not at all trivial, so there is a small chance that this
change may regress any drivers incorrectly relying on mmiowb() to order
MMIO writes between CPUs using lock-free synchronisation.” The mmio in
radeon_ring_commit() is protected by a mutex rather than a spinlock, but in
the mutex fastpath it behaves similar to spinlock. We can add mmiowb()
calls in the radeon driver but the maintainer says he doesn’t like such a
workaround, and radeon is not the only example of mutex protected mmio. So
we should extend the mmiowb tracking system from spinlock to mutex, and
maybe other locking primitives. This is not easy and error prone, so we
solve it in the architectural code, by simply defining the __io_aw() hook
as mmiowb(). And we no longer need to override queued_spin_unlock() so use
the generic definition. Without this, we get such an error when run
‘glxgears’ on weak ordering architectures such as LoongArch: radeon
0000:04:00.0: ring 0 stalled for more than 10324msec radeon 0000:04:00.0:
ring 3 stalled for more than 10240msec radeon 0000:04:00.0: GPU lockup
(current fence id 0x000000000001f412 last fence id 0x000000000001f414 on
ring 3) radeon 0000:04:00.0: GPU lockup (current fence id
0x000000000000f940 last fence id 0x000000000000f941 on ring 0) radeon
0000:04:00.0: scheduling IB failed (-35). [drm:radeon_gem_va_ioctl
[radeon]] ERROR Couldn’t update BO_VA (-35) radeon 0000:04:00.0:
scheduling IB failed (-35). [drm:radeon_gem_va_ioctl [radeon]] ERROR
Couldn’t update BO_VA (-35) radeon 0000:04:00.0: scheduling IB failed
(-35). [drm:radeon_gem_va_ioctl [radeon]] ERROR Couldn’t update BO_VA
(-35) radeon 0000:04:00.0: scheduling IB failed (-35).
[drm:radeon_gem_va_ioctl [radeon]] ERROR Couldn’t update BO_VA (-35)
radeon 0000:04:00.0: scheduling IB failed (-35). [drm:radeon_gem_va_ioctl
[radeon]] ERROR Couldn’t update BO_VA (-35) radeon 0000:04:00.0:
scheduling IB failed (-35). [drm:radeon_gem_va_ioctl [radeon]] ERROR
Couldn’t update BO_VA (-35) radeon 0000:04:00.0: scheduling IB failed
(-35). [drm:radeon_gem_va_ioctl [radeon]] ERROR Couldn’t update BO_VA
(-35)

Notes