Re: [PATCH v2] KVM: arm64: Fix error path in init_hyp_mode()

[Quentin Perret <qperret@google.com>]

On Wednesday 25 Jun 2025 at 12:30:58 (+0000), Mostafa Saleh wrote:
> In the unlikely case pKVM failed to allocate carveout, the error path
> tries to access NULL ptr when it de-reference the SVE state from the
> uninitialized nVHE per-cpu base.
> 
> [    1.575420] pstate: 61400005 (nZCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--)
> [    1.576010] pc : teardown_hyp_mode+0xe4/0x180
> [    1.576920] lr : teardown_hyp_mode+0xd0/0x180
> [    1.577308] sp : ffff8000826fb9d0
> [    1.577600] x29: ffff8000826fb9d0 x28: 0000000000000000 x27: ffff80008209b000
> [    1.578383] x26: ffff800081dde000 x25: ffff8000820493c0 x24: ffff80008209eb00
> [    1.579180] x23: 0000000000000040 x22: 0000000000000001 x21: 0000000000000000
> [    1.579881] x20: 0000000000000002 x19: ffff800081d540b8 x18: 0000000000000000
> [    1.580544] x17: ffff800081205230 x16: 0000000000000152 x15: 00000000fffffff8
> [    1.581183] x14: 0000000000000008 x13: fff00000ff7f6880 x12: 000000000000003e
> [    1.581813] x11: 0000000000000002 x10: 00000000000000ff x9 : 0000000000000000
> [    1.582503] x8 : 0000000000000000 x7 : 7f7f7f7f7f7f7f7f x6 : 43485e525851ff30
> [    1.583140] x5 : fff00000ff6e9030 x4 : fff00000ff6e8f80 x3 : 0000000000000000
> [    1.583780] x2 : 0000000000000000 x1 : 0000000000000002 x0 : 0000000000000000
> [    1.584526] Call trace:
> [    1.584945]  teardown_hyp_mode+0xe4/0x180 (P)
> [    1.585578]  init_hyp_mode+0x920/0x994
> [    1.586005]  kvm_arm_init+0xb4/0x25c
> [    1.586387]  do_one_initcall+0xe0/0x258
> [    1.586819]  do_initcall_level+0xa0/0xd4
> [    1.587224]  do_initcalls+0x54/0x94
> [    1.587606]  do_basic_setup+0x1c/0x28
> [    1.587998]  kernel_init_freeable+0xc8/0x130
> [    1.588409]  kernel_init+0x20/0x1a4
> [    1.588768]  ret_from_fork+0x10/0x20
> [    1.589568] Code: f875db48 8b1c0109 f100011f 9a8903e8 (f9463100)
> [    1.590332] ---[ end trace 0000000000000000 ]---
> 
> As Quentin pointed, the order of free is also wrong, we need to free
> SVE state first before freeing the per CPU ptrs.
> 
> I initially observed this on 6.12, but I could also repro in master.
> 
> Signed-off-by: Mostafa Saleh <smostafa@google.com>

Probably worth adding:

  Fixes: 66d5b53e20a6 ("KVM: arm64: Allocate memory mapped at hyp for host sve state in pKVM")

With that:

  Reviewed-by: Quentin Perret <qperret@google.com>

Thanks,
Quentin